Haloheterocycles and Cross-Coupling: A Research-Oriented Selection Framework from Substrate Identification to Bond-Forming Routes (Including Product Navigation and Tables 1–5)

I. Introduction

Haloheterocycles have long occupied an important place in modern organic synthesis not simply because they are “heterocycles bearing halogens,” but because they simultaneously provide two layers of information: the heterocyclic core and an editable site. The former determines the molecule's fundamental electronic environment, polarity, coordination characteristics, and potential bioactivity background; the latter provides a clearly defined entry point for subsequent structural modification.

Cross-coupling is the key tool that turns this “editable entry point” into real structural diversity. The 2010 Nobel Prize in Chemistry was awarded to Heck, Negishi, and Suzuki for palladium-catalyzed cross-couplings in organic synthesis. Judging from the core content recognized by the Nobel Prize, the representative contribution centered primarily on C–C bond-forming methodology; in practical impact, however, the value of this class of reactions has long extended far beyond a single bond type and is now widely applied in medicinal chemistry, materials chemistry, and the synthesis of complex organic molecules.

II. Basic Concepts and the Focus of This Article

Module	Core meaning	Focus of this article
Heterocycle	An organic cyclic compound containing at least one non-carbon atom in the ring	Acts as the molecular core scaffold and determines the fundamental electronic environment and structural characteristics
Haloheterocycle	A compound formed by introducing one or more halogen atoms onto a heterocyclic scaffold	Focus here is on substrate platforms that can serve as entry points for subsequent coupling
Cross-coupling	A bond-forming method that joins two fragments under metal catalysis	Focus here is on haloheterocycle-directed C–C, C–N, and C–O bond formation
Main thread of this article	From “substrate platform” to “target bond formation”	To establish a selection framework

III. Why Haloheterocycles Are High-Value Building Blocks

1. The most important value of haloheterocycles is that they are often not the endpoint of synthesis, but the starting point for further elaboration. A haloheterocycle can often serve as a common intermediate and, while retaining the heterocyclic core, can be diversified through different reactions to introduce aryl, heteroaryl, amino, alkynyl, or alkoxy groups, thereby yielding a series of structurally related derivatives with different properties.

2. Even more importantly, haloheterocycles simultaneously provide two layers of information that can be used separately: the heterocyclic core determines the molecule's fundamental electronic environment, polarity, and scaffold characteristics, while the halogenated position provides the reactive entry point for subsequent bond construction. Because these two elements can be combined strategically, haloheterocycles are especially well suited to series optimization, comparative modification at different connection sites, and structure–activity relationship studies.

3. In this sense, cross-coupling is not simply a matter of “attaching a group”; rather, it is a way to efficiently expand a chosen heterocyclic scaffold into a family of structurally related derivatives. This allows researchers to systematically vary substituent types and connection patterns while retaining the core scaffold.

IV. Functional Roles of the Three Main Pathways: C–C, C–N, and C–O Bond Formation

Bond-forming track	Primary objective	Common fragments introduced	Representative methods	Typical role in heterocycle design
C–C	Expand or modify the carbon framework	Aryl, heteroaryl, alkenyl, alkynyl	Suzuki–Miyaura, Sonogashira, Heck, Negishi, Stille	Rapid scaffold expansion; tuning conjugation and spatial geometry
C–N	Introduce amine functionality	Primary amines, secondary amines, heterocyclic amines, etc.	Buchwald–Hartwig amination	Introduces nitrogen-containing functional sites and tunes basicity, polarity, hydrogen bonding, and medicinal-chemistry properties
C–O	Construct aryloxy or alkoxy substitution patterns	Phenols, alcohols, alkoxy fragments	Pd-catalyzed O-arylation / alkoxylation; for some substrates, Cu-catalyzed Ullmann-type C–O coupling is also common, and SNAr should be evaluated for electron-deficient N-heterocycles	Tunes electronic effects, substitution patterns, and downstream derivatization space

V. Three Common Method Classes in “Haloheterocycle–Cross-Coupling” Chemistry

Method	Core problem addressed	Typical coupling partners	Method features	Typical use scenarios
Suzuki–Miyaura	Introduce aryl / heteroaryl groups onto a heterocyclic scaffold	Various organoboron reagents	Highly general and well suited to rapidly generating a family of scaffold variants	Scaffold expansion and systematic SAR studies
Buchwald–Hartwig amination	Install amine fragments onto a heterocyclic scaffold	Various amines	A classical and highly general method for constructing C–N bonds	Amination, polarity tuning, and medicinal-chemistry-oriented modification
Sonogashira	Introduce alkynyl groups onto a heterocyclic scaffold	Terminal alkynes	Introduces linear alkynyl linking units with strong downstream extendability	Conjugation extension, linker chemistry, and further functionalization

VI. Key Factors to Consider in Cross-Coupling of Haloheterocycles

Factor	Why it matters	How to think about it
Halogen identity	Influences C–X bond cleavage and the ease of oxidative addition	Do not look only at the empirical order I > Br > Cl; the specific substrate must also be considered
Heterocyclic core	Changes electronic distribution, polarity, and coordination behavior	Different heterocycles can differ dramatically in coupling reactivity
Site pattern	Determines which position is better suited as the connection point	For polyhalogenated substrates, sequence and selectivity are especially important
Catalytic system	Controls activation, selectivity, and side-reaction suppression	Ligand, metal, base, and solvent often determine whether the reaction works at all
Type of coupling partner	Affects transmetalation, reductive elimination, and substrate compatibility	The same haloheterocycle may require different conditions when the coupling partner changes

Why is halogen order alone not enough?

1. Halogen order can only serve as a preliminary rule of thumb within a specific context, not as a universal rule for all aromatic substitution reactions.

In Pd-catalyzed cross-coupling, especially when oxidative addition / substrate activation difficulty is used as an initial guide, Ar–I > Ar–Br > Ar–Cl > Ar–F can often be taken as a general trend for substrate reactivity. Accordingly, in many cross-coupling designs, aryl or heteroaryl iodides and bromides are usually considered before the corresponding chlorides.

But this order cannot be mechanically extrapolated to all aromatic substitution reactions. Once the chemistry enters the domain of nucleophilic aromatic substitution (SNAr), leaving-group behavior can be quite different: in classical SNAr on activated aromatic rings, the familiar “element effect” often appears as F > Cl ≈ Br > I. In other words, the Ar–F class that is typically hardest to activate in Pd cross-coupling is not necessarily the least reactive in SNAr. Therefore, “halogen order” is only a local heuristic once the reaction mode is clear, and should not be used independently of mechanistic context.

2. Heterocyclic substrates, in particular, cannot be interpreted simply by applying a “halogen reactivity order.”

The presence of heteroatoms changes the electronic distribution, degree of polarization, and metal-coordination behavior at different positions on the ring. As a result, the actual reactivity of heterocyclic substrates often depends not only on whether the leaving group is Br or Cl, but also on the heterocycle type, the halogenation site, and the overall substrate architecture. For polyhalogenated heterocycles, site selectivity is often jointly determined by the intrinsic polarization of the ring carbons and the halogen identity, rather than by a simple ranking of which halogen is “more reactive.”

It is also important to note that N-containing haloheterocycles should not all be interpreted first through the lens of Pd-catalyzed C–N coupling. For electron-deficient N-containing haloheterocycles, especially pyrimidines, pyrazines, quinazolines, and related systems, the first question in reactions with amines is often whether nucleophilic aromatic substitution (SNAr) should be evaluated, rather than moving directly into Buchwald–Hartwig amination screening. Classical electrophilic substrates such as 4-chloroquinazoline have long been widely used in medicinal chemistry for amination, and substrates such as 2,4-dichloropyrimidine also have literature precedent for regioselective SNAr amination. Therefore, in transformations of the type “haloheterocycle + amine,” a more reliable decision order is often not to search for ligands first, but to ask whether the substrate is already sufficiently electron-deficient and intrinsically suited to direct SNAr.

3. The most reliable approach is to distinguish the reaction mode first and only then discuss halogen trends.

If the target transformation is a metal-catalyzed cross-coupling such as Suzuki, Buchwald–Hartwig, or Sonogashira, then halogen identity is indeed an important reference factor. But if the substrate is an obviously electron-deficient N-heterocycle and the coupling partner is an amine, alkoxide, or another nucleophile, it is also necessary to judge whether the system is closer to an SNAr reaction window. In other words, when making research-oriented route choices, the first question should not be “Which halogen is more reactive?” but rather “Which reaction mode is this substrate more likely to follow under the current transformation objective?” Only after that distinction is made does discussion of halogen order become truly reliable.

VII. A Five-Step Selection Framework from Substrate to Route

Step	Core question	Selection focus
Step 1	Which heterocyclic core should be chosen?	First define the fundamental electronic environment, polarity, aromaticity, coordination characteristics, and potential application background; these are the basis for subsequent site reactivity, reaction mode, and property tuning.
Step 2	Which halogenated position should be chosen?	Define the subsequent connection site and judge whether the position is suitable for sequential modification; for polyhalogenated substrates, positional differences and regioselectivity deserve special attention.
Step 3	What bond needs to be formed?	First clarify whether the target is a C–C, C–N, or C–O bond; this determines whether Suzuki / Sonogashira / Buchwald–Hartwig or another more direct substitution route should be prioritized.
Step 4	Is metal catalysis truly necessary?	For clearly electron-deficient N-containing haloheterocycles, especially pyrimidines, pyrazines, quinazolines, and related systems, first judge whether the target transformation can already be achieved directly through SNAr / nucleophilic substitution; if the substrate is intrinsically reactive enough, direct substitution is often more straightforward and economical than beginning with metal-catalyzed screening.
Step 5	If metal catalysis is needed, how should the system be screened?	After confirming that cross-coupling is required, then match Pd / Ni / Cu, ligands, bases, solvents, and additives according to the substrate features, coupling partner, and target bond type. In general, Pd remains the preferred starting point for most standard cross-couplings; Ni is more suitable for side-by-side comparison in specific substrates, sp³ couplings, or special electronic systems; Cu has practical value in certain C–N, C–O, and Sonogashira-related systems.

VIII. Key Practical Considerations in Haloheterocycle Cross-Coupling

Practical consideration	What should be prioritized experimentally?	Why it matters
Different haloheterocycles cannot be handled by simply applying one set of conditions	First examine the heterocycle type, halogenation site, and substrate electronics, and then decide on the coupling route and catalytic system	Differences among heterocyclic substrates are often substantial; this is especially true for N-heterocycles, fused heterocycles, and polyhalogenated substrates, whose actual behavior can differ markedly
When choosing a route, do not focus only on reaction names	First clarify whether the goal is C–C, C–N, or C–O bond formation, and then choose the corresponding method	What really determines experimental design is usually not the reaction name itself, but whether the target bond type matches the substrate and coupling partner
N-containing heterocycles often require closer attention to catalytic-system matching	Pay particular attention to the catalyst, ligand, base, and solvent	N-containing heterocycles can alter substrate electronics and may also coordinate to the metal center, so they are often more condition-sensitive than ordinary aryl substrates
C–O coupling should not be treated too simply by analogy with C–N coupling	The ligand, base, oxygen nucleophile type, and side-reaction control all need to be evaluated separately	C–O coupling is often more condition-sensitive and can be just as challenging to optimize
Polyhalogenated or differentiated dihalogenated substrates require separate analysis of site order	Focus on which site should couple first and which should be reserved for the next step	Such substrates are often used in sequential coupling and series construction, so site assignment can directly determine whether the route design is viable

IX. Product Navigation for Haloheterocycles and Cross-Coupling: Quickly Locate Tables 1–5 by Research Task

Research task / experimental need	Product types to prioritize	Which table to consult first	How to use it
Need to choose a suitable N-containing haloheterocyclic electrophilic substrate as the starting point for subsequent coupling	Halopyridines, pyrimidines, pyrazines, pyridazines, quinazolines, quinolines, and pyridyl triflates	Table 1	Table 1 concentrates six-membered N-heterocycles, fused N-heterocycles, and pseudohalide substrates. It is the first substrate table to consult for medicinal-chemistry scaffold modification, heterocycle platform construction, and site selection.
Want to carry out coupling-based modification of five-membered heteroaryls such as thiophene, furan, thiazole, and pyrazole	Five-membered halogenated heteroaryl substrates	Table 2	Table 2 focuses on five-membered heteroaryl substrates and is well suited to conjugation extension, heterocycle-fragment introduction, methodology development on five-membered ring scaffolds, or materials-related molecular construction.
Want to run a Suzuki–Miyaura coupling and need organoboron partners	Aryl boronic acids, heteroaryl boronic acids, boronate esters, potassium trifluoroborates, MIDA boron derivatives, and diboron reagents	Table 3	Table 3 is the core companion table for the Suzuki track. It contains both direct coupling partners and more stable organoboron surrogates or borylation precursors, making it useful when introducing aryl / heteroaryl groups.
Want to perform Buchwald–Hartwig amination and install amine fragments onto a haloheterocycle	Aminic coupling partners such as anilines, benzylamine, morpholine, piperidine, and piperazine	Table 4	Table 4 brings together common nucleophiles used in C–N coupling and is especially useful for introducing N-containing side chains and tuning polarity in medicinal-chemistry optimization.
Want to perform C–O coupling and build aryloxy or alkoxy-substituted structures	Phenol, substituted phenols, and other oxygen nucleophiles	Table 4	Table 4 is not limited to amination; it also covers common oxygen nucleophiles used in C–O coupling. When the goal is to attach a phenoxy group to a haloheterocycle, this is the table to consult first.
Want to perform Sonogashira coupling and attach an alkynyl group to a haloheterocycle	Phenylacetylene, substituted arylacetylenes, and TMS-protected acetylene	Table 4	Table 4 lists the most common terminal alkynes and protected alkyne sources for the Sonogashira track, making it useful for alkynyl extension, linker chemistry, and further downstream transformation.
The substrate and coupling partner have already been chosen, and the next step is to find catalysts, ligands, and bases	Pd / Ni catalysts, Buchwald ligands, bases, CuI, and Tf₂O	Table 5	Table 5 is the condition-system table. It is best consulted after the reaction type is clear and is useful for Pd vs Ni screening, ligand switching, base optimization, and cocatalyst selection.
Want to work on difficult substrates or compare different catalytic systems	Pd(dppf)Cl₂, Pd(PPh₃)₄, Pd₂(dba)₃, XPhos / SPhos / BrettPhos / RuPhos, and Ni precursors	Table 5	When the substrate is strongly electron-deficient, contains multiple heteroatoms, is sterically hindered, or when Pd / Ni routes are to be compared, Table 5 is especially informative.
Want to perform sequential coupling, dual-site modification, or regioselective construction	Dihalogenated substrates, differentiated dihalogenated substrates, and dual-site five-membered heterocycle substrates	Tables 1 and 2	Tables 1 and 2 include 2,4- / 2,5-dihalogenated N-heterocycles, Br/Cl-differentiated substrates, and examples such as 2,5-dibromothiophene, making them especially useful for multistep, sequential, and site-programmable construction.
Want to rapidly expand one heterocyclic scaffold into a family of derivatives	Haloheterocycle substrates + organoboron coupling partners	Table 1 / Table 2 + Table 3	If the research focus is to append different aryl / heteroaryl groups to the same core scaffold, the most practical approach is to select the electrophilic substrate from Table 1 or Table 2 first, and then choose the corresponding organoboron partners from Table 3.
Want to turn one heterocyclic scaffold into a series of nitrogen-containing derivatives	Haloheterocycle substrates + amine coupling partners	Table 1 / Table 2 + Table 4	When the goal is a series of C–N coupling modifications, it is advisable to choose the substrate first from Table 1 or Table 2 and then identify the appropriate amine fragment in Table 4.
Want to convert a non-halogenated substrate into a coupling entry point before entering a cross-coupling route	Triflate precursor activating reagents and pseudohalide substrates	Table 5, together with Table 1	If the starting site is not a halogen but a hydroxyl group or a related precursor, first consult the activating reagents in Table 5 and then design the route in combination with the pseudohalide substrate logic in Table 1.

Table 1. Six-Membered N-Heterocyclic Halo / Pseudohalide / Fused Heteroaryl Substrates (Main Electrophilic Substrate Track for Cross-Coupling)

Category	CAS No.	Aladdin Cat. No.	Name	Grade or purity	Product features and applications
Six-membered N-heteroaryl monohalide (chloropyridine)	109-09-1	C474470	2-Chloropyridine	99%	A foundational haloheterocyclic building block; 2-chloropyridine is commonly used in Suzuki, amination, and other couplings, making it a high-frequency substrate in medicinal chemistry and heterocycle methodology.
Six-membered N-heteroaryl monohalide (bromopyridine)	109-04-6	B109679	2-Bromopyridine	≥98%	A classical halopyridine building block; commonly used in Suzuki, Sonogashira, C–N coupling, and subsequent metalation-based transformations, and one of the most common heterocyclic substrates.
Six-membered N-heteroaryl monohalide (bromopyridine)	626-55-1	B106977	3-Bromopyridine	≥98%	A commonly used monohalopyridine building block; used in C–C, C–N, Sonogashira, and related couplings, and a frequent substrate for heterocycle modification.
Six-membered N-heteroaryl monohalide (chloropyrimidine)	1722-12-9	C132282	2-Chloropyrimidine	≥99%(GC)	An electron-deficient diazine chloride substrate; commonly used in amination and Suzuki coupling, and a common entry point for medicinal chemistry and N-heterocycle modification.
Six-membered N-heteroaryl monohalide (bromopyrimidine)	4595-60-2	B120301	2-Bromopyrimidine	≥98%	A commonly used monobromopyrimidine substrate; suitable for Suzuki, amination, and related couplings in diazine-scaffold modification.
Six-membered N-heteroaryl monohalide (bromopyrimidine)	4595-59-9	B107005	5-Bromopyrimidine	≥98%	Another commonly used bromopyrimidine positional isomer; well suited to comparing site effects and building derivative series.
Six-membered N-heteroaryl monohalide (chloropyrazine)	14508-49-7	C124227	2-Chloropyrazine	≥98%	An electron-deficient chlorinated diazine; suitable for amination and C–C coupling, and a common substrate in medicinal chemistry and electron-deficient heterocycle methodology.
Six-membered N-heteroaryl monohalide (bromopyrazine)	56423-63-3	B135014	2-Bromopyrazine	≥97%	An electron-deficient brominated diazine substrate; commonly used in Suzuki and amination, and a common entry point for heterocycle medicinal-chemistry modification.
Six-membered N-heteroaryl monohalide (bromopyridazine)	88491-61-6	B590520	3-Bromopyridazine	≥97%	A representative pyridazine-type electrophilic substrate; suitable for Suzuki, Sonogashira, or amination, and useful for expanding polyaza heterocyclic scaffolds.
Fused N-heteroaryl monohalide (chloroquinazoline)	5190-68-1	C123527	4-Chloroquinazoline	≥97%	A classical quinazoline modification entry point; in medicinal chemistry, substituents are often introduced further through C–N or C–C coupling.
Six-membered N-heteroaryl dihalide (dichloropyridine)	16110-09-1	D120567	2,5-Dichloropyridine	≥99%	Contains two editable sites; suitable for sequential coupling or site-selective modification, and useful for rapidly building pyridine derivative series.
Six-membered N-heteroaryl dihalide (dichloropyridine)	26452-80-2	D154414	2,4-Dichloropyridine	≥98%(GC)	A commonly used differentiated-site dihalide substrate; suitable for comparing site reactivity and conducting sequential coupling / regioselective construction.
Six-membered N-heteroaryl dihalide (dibromopyridine)	625-92-3	D115760	3,5-Dibromopyridine	≥98%	A typical dual-site halopyridine substrate; suitable for sequential coupling, difunctionalization, and the construction of symmetrical / unsymmetrical derivatives.
Differentiated dihalogenated six-membered N-heteroaryl substrate	40473-01-6	B102594	2-Bromo-5-chloropyridine	≥98%	Contains two differentiated leaving-group sites, Br and Cl; especially well suited to stepwise sequential coupling and regioselective construction, and a representative platform substrate.
Six-membered N-heteroaryl dihalide (dichloropyrimidine)	3934-20-1	D103228	2,4-Dichloropyrimidine	≥98%	A highly reactive diazine dihalide substrate; especially suitable for sequential amination, Suzuki coupling, or multistep platform-style modification based on site differences.
Six-membered N-heteroaryl dihalide (dichloropyrimidine)	1193-21-1	D106524	4,6-Dichloropyrimidine	≥98%	A highly reactive diazine dihalide substrate; suitable for regioselective substitution, sequential coupling, and platform-style derivatization.
Fused N-heteroaryl dihalide (quinazoline type)	607-68-1	D185530	2,4-Dichloroquinazoline	≥95%	A dual-site quinazoline platform substrate; suitable for sequential coupling and multi-site modification, and a common core scaffold in structure–activity relationship studies.
Fused N-heteroaryl dihalide (quinoline type)	86-98-6	D155356	4,7-Dichloroquinoline	≥98%(GC)	A fused N-heterocycle building block; commonly used for quinoline scaffold modification and also suitable for dual-site extension and structure–activity relationship studies.
Six-membered N-heteroaryl pseudohalide (pyridyl triflate)	65007-00-3	P160048	2-Pyridyl Trifluoromethanesulfonate	≥98%(GC)	A 2-pyridyl triflate-type pseudohalide substrate; used in place of certain halopyridines to enter cross-coupling routes and suitable for site-diversified design.
Six-membered N-heteroaryl pseudohalide (pyridyl triflate)	107658-27-5	P160508	3-Pyridyl Trifluoromethanesulfonate	≥98%	A representative heteroaryl triflate electrophilic substrate; used to bring pseudohalide substrates into Suzuki, amination, and related cross-coupling systems.

Table 2. Five-Membered Halogenated Heteroaryl Substrates (Thiophene / Furan / Thiazole / Pyrazole)

Category	CAS No.	Aladdin Cat. No.	Name	Grade or purity	Product features and applications
Five-membered sulfur heteroaryl monohalide (bromothiophene)	1003-09-4	B107006	2-Bromothiophene	≥98%	A representative five-membered sulfur heteroaryl electrophilic substrate; commonly used in Suzuki, Sonogashira, and other C–C couplings to introduce thiophene fragments into target molecules or serve as a further functionalization platform.
Five-membered sulfur heteroaryl monohalide (bromothiophene)	872-31-1	B103164	3-Bromothiophene	≥97%	A common thiophene cross-coupling substrate; used to build substituted thiophene structures and conjugation-extending units.
Five-membered sulfur heteroaryl dihalide (dibromothiophene)	3141-27-3	D100660	2,5-Dibromothiophene	≥96%	A dual-site thiophene substrate; suitable for sequential coupling, bidirectional extension, and conjugated-material scaffold construction.
Five-membered oxygen heteroaryl monohalide (bromofuran)	584-12-3	B665004	2-Bromofuran	≥93%	A reactive bromofuran building block; suitable for rapid introduction of a furan unit through C–C coupling.
Five-membered oxygen heteroaryl monohalide (bromofuran)	22037-28-1	B123116	3-Bromofuran	≥97%	A reactive five-membered oxygen heteroaryl substrate; commonly used in C–C coupling to append furan fragments to target molecules.
Five-membered sulfur/nitrogen heteroaryl monohalide (bromothiazole)	3034-53-5	B123649	2-Bromothiazole	≥99%	A relatively reactive five-membered heteroaryl electrophilic substrate; commonly used in Suzuki, Sonogashira, and amination to introduce thiazole fragments.
Five-membered sulfur/nitrogen heteroaryl monohalide (bromothiazole)	34259-99-9	B122730	4-Bromothiazole	≥97%	A commonly used bromothiazole substrate; suitable for Suzuki, Sonogashira, and related couplings to introduce thiazole heteroaryl fragments.
Five-membered nitrogen heteroaryl monohalide (bromopyrazole)	14521-80-3	B132639	3-Bromopyrazole	≥97%	A representative five-membered nitrogen heteroaryl substrate; suitable for building substituted pyrazole derivatives and useful in medicinal chemistry and heterocycle methodology research.

Table 3. Organoboron Coupling Partners and Borylation Precursors (Suzuki–Miyaura Track)

Category	CAS No.	Aladdin Cat. No.	Name	Grade or purity	Product features and applications
Aryl boronic acid coupling partner	98-80-6	P396095	Phenylboronic acid (PBA) (contains varying amounts of Anhydride)	≥99.5%	One of the most fundamental Suzuki–Miyaura coupling partners; used to introduce phenyl groups into haloheterocycles and build biaryl or aryl-substituted heterocycles.
Aryl boronate ester coupling partner	24388-23-6	P119610	Phenylboronic Acid Pinacol Ester	≥98%	A commonly used phenyl Suzuki coupling partner; more stable than some boronic acids and well suited to method development and condition screening.
Stable organoboron surrogate	153766-81-5	P160808	Potassium Phenyltrifluoroborate	≥98%	A stable phenyl organoboron reagent; used in Suzuki coupling to introduce phenyl groups and offers good handling and storage stability.
Substituted aryl boronic acid coupling partner	5720-07-0	M109431	4-Methoxybenzeneboronic Acid (contains varying amounts of Anhydride)	≥95%	A commonly used para-methoxy aryl Suzuki coupling partner for introducing electron-donating aryl fragments.
Heteroaryl boronic acid coupling partner	6165-68-0	T107124	2-Thienylboronic acid(contains varying amounts of Anhydride)	≥98%	A representative heteroaryl boronic acid; used in Suzuki coupling to append a thiophene unit to haloheterocycles and construct heteroaryl–heteroaryl linked scaffolds.
Heteroaryl boronic acid coupling partner	1692-25-7	P396303	3-Pyridineboronic acid (contains varying amounts of Anhydride)	≥98%	A typical 3-pyridyl Suzuki coupling partner used to append a pyridine unit to haloheterocyclic scaffolds.
Heteroaryl boronate ester coupling partner	329214-79-1	T162805	3-(4,4,5,5-Tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine	≥98%	A stable pyridyl boronate ester-type Suzuki partner; suitable for introducing a 3-pyridyl fragment into haloheterocycles.
Stable heteroaryl organoboron surrogate	561328-69-6	P138999	Potassium pyridine-3-trifluoroborate	≥98%	A stable 3-pyridyl Suzuki coupling partner; easier to store and handle than the corresponding boronic acid, and suitable for heteroaryl introduction.
Heteroaryl boronic acid coupling partner	197958-29-5	P123314	Pyridine-2-boronic acid(contains varying amounts of Anhydride)	≥95%	A 2-pyridyl Suzuki coupling partner that can directly introduce a neighboring N-containing heteroaryl fragment, although its stability often requires attention in practice.
Stable heteroaryl boronic acid surrogate	1104637-58-2	P165911	2-Pyridylboronic acid MIDA ester	≥95%	A stable 2-pyridyl organoboron surrogate; used to address the stability and handling issues of 2-pyridylboronic acid and suitable for Suzuki coupling.
Diboron reagent / borylation precursor	73183-34-3	B396365	Bis(pinacolato)diboron	≥99%	One of the most commonly used diboron reagents; used in Miyaura borylation to prepare aryl / heterocyclic boronate esters and serves as an important precursor for the “borylation first, then Suzuki” route.
Hydroboration / borylation reagent	25015-63-8	T113748	4,4,5,5-Tetramethyl-1,3,2-dioxaborolane	≥97%	A commonly used HBpin borylation reagent; used in hydroboration or in building organoboron intermediates from other substrates, thereby serving subsequent Suzuki routes.

Table 4. Amine / Phenol / Alkyne Coupling Partners (C–N / C–O / Sonogashira Track)

Category	CAS No.	Aladdin Cat. No.	Name	Grade or purity	Product features and applications
Aniline coupling partner (basic aniline feedstock)	62-53-3	A112120	Aniline	AR, ≥99.5%,	One of the most basic and commonly used aromatic amine coupling partners; suitable for Buchwald–Hartwig amination, Ullmann-type C–N coupling, and some nucleophilic substitution routes, and used to introduce an aniline fragment into haloheterocycles. It is a representative feedstock for C–N bond-formation screening, method development, and aromatic amine derivative construction.
Substituted aniline coupling partner	104-94-9	A106071	p-Anisidine	≥99%	A typical para-methoxy-substituted aniline; used in Buchwald–Hartwig amination to introduce electron-rich aniline fragments and tune electronic properties.
Benzylamine coupling partner	100-46-9	B108477	Benzylamine	AR, ≥99%	A commonly used monoamine coupling partner; introduces a benzylamine fragment into haloheterocycles through C–N coupling and offers further derivatization and side-chain extension potential.
Heterocyclic amine coupling partner (morpholine introduction)	110-91-8	M109058	Morpholine	Distilled grade, ≥99.5%	A commonly used oxygen-containing six-membered cyclic amine; used in C–N coupling to introduce a morpholine unit and help tune polarity, basicity, and drug-like properties.
Heterocyclic amine coupling partner (piperidine introduction)	110-89-4	P1506301	Piperidine	AR,≥99.5%	A typical secondary amine coupling partner; used in Buchwald–Hartwig C–N coupling to introduce a piperidine unit into haloheterocycles and is a high-frequency fragment in medicinal-chemistry optimization.
Heterocyclic diamine coupling partner (piperazine introduction)	110-85-0	P755827	Piperazine	UltraBio™, anhydrous, ≥99%(T)	A typical diamine-type coupling partner; used in haloheterocycle amination to introduce a piperazine motif and is a high-frequency polar fragment in medicinal chemistry.
C–O coupling oxygen nucleophile (basic phenol feedstock)	108-95-2	P100770	Phenol	≥99.5%(GC)	One of the most basic and commonly used phenolic oxygen nucleophiles; suitable for Pd- or Cu-catalyzed C–O coupling and can also serve as a nucleophilic substitution partner for some electron-deficient heterocyclic substrates. It is used to build aryloxy or diaryl ether structures and is a representative feedstock for O-arylation condition screening, method development, and aryloxy-fragment introduction.
C–O coupling oxygen nucleophile (substituted phenol)	150-76-5	M104222	4-Methoxyphenol（MEHQ）	AR, ≥99%	A representative substituted phenolic oxygen nucleophile; can be used to construct aryloxy / diaryl ether structures and also serves as a model fragment for electron-donating substituent effects.
Aryl terminal alkyne coupling partner	536-74-3	P107030	Phenylacetylene	≥97%	One of the most classical terminal alkynes in Sonogashira coupling; used to attach a phenylacetylenyl group to haloheterocycles and extend conjugation.
Aryl terminal alkyne coupling partner	768-60-5	M111332	4-Methoxyphenylacetylene	≥99%	A representative Sonogashira coupling partner; introduces a para-methoxy aryl alkyne into haloheterocycles for conjugation extension and electronic-effect tuning.
Deprotectable alkyne source / alkynyl-transfer precursor	1066-54-2	E106615	(Trimethylsilyl)acetylene	≥98%	A protected alkyne source; can participate in coupling first and then undergo TMS deprotection, helping reduce terminal-alkyne self-polymerization or other side-reaction risks.

Table 5. Catalysts, Ligands, Bases, Cocatalysts, and Activating Reagents (Condition-System Module)

Category	CAS No.	Aladdin Cat. No.	Name	Grade or purity	Product features and applications
Classical Pd(0) catalyst	14221-01-3	T111021	Tetrakis(triphenylphosphine)palladium(0)	Pd ≥8.9%	A classical preformed Pd(0) catalyst; suitable for many types of C–C / C–N / C–O cross-coupling and a common starting choice in method development and literature reproduction.
Common Pd(II) precatalyst	72287-26-4	D107566	[1,1′-Bis(diphenylphosphino)ferrocene]dichloropalladium	Pd 14.5%	A classical Pd(dppf)Cl₂-type system; commonly used in Suzuki, Sonogashira, Negishi, and related couplings, with good compatibility toward haloheterocycles and heteroaryl coupling partners.
Common Pd(0) source	51364-51-3	T284022	Tris(dibenzylideneacetone)dipalladium(0)	≥99.95% metals basis	A commonly used Pd(0) precursor; often combined with phosphine ligands for condition screening in Suzuki, Buchwald–Hartwig, Sonogashira, and related systems.
Buchwald-type Pd precatalyst (XPhos Pd G2)	1310584-14-5	X294162	XPhos Pd G2	≥99.95% metals basis	A Buchwald-type precatalyst using XPhos as the ligand; suitable for condition development in C–N and selected C–C / C–O couplings, and convenient for in situ generation of the active species.
Buchwald-type Pd precatalyst (XPhos Pd G3)	1445085-55-1	X294596	XPhos Pd G3	≥99.95% metals basis	A third-generation XPhos precatalyst; especially common in Suzuki–Miyaura and related couplings, with fast activation, a defined ligand / metal ratio, and convenient handling.
Buchwald ligand (XPhos)	564483-18-7	D102808	2-Dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl	≥97%	A high-frequency Buchwald ligand; widely used in Suzuki, Buchwald–Hartwig, and some C–O coupling condition development.
Buchwald ligand (SPhos)	657408-07-6	D105523	2-Dicyclohexylphosphino-2′,6′-dimethoxybiphenyl	≥98%	A highly general Buchwald ligand; commonly used in Suzuki–Miyaura, especially for aryl / heteroaryl chlorides and sterically demanding substrates.
Buchwald ligand (RuPhos)	787618-22-8	D115625	2-Dicyclohexylphosphino-2′,6′-diisopropoxybiphenyl	≥98%	A commonly used biaryl phosphine ligand; suitable for more challenging C–N, C–O, and selected C–C couplings, especially in screening hard-to-activate substrates.
Buchwald ligand (BrettPhos)	1070663-78-3	B137987	Dicyclohexyl(2',4',6'-triisopropyl-3,6-dimethoxy-[1,1'-biphenyl]-2-yl)phosphine	≥97%	A representative Buchwald biaryl phosphine ligand; commonly used in challenging C–N and C–O couplings, especially for difficult substrates.
Ni(II) catalyst / precatalyst	14647-23-5	D101082	[1,2-Bis(diphenylphosphino)ethane]dichloronickel(II)	≥98%	A common nickel catalyst precursor; used to build Ni-catalyzed cross-coupling systems and suitable for side-by-side comparison with Pd routes or for development on specific substrates.
Ni(0) catalyst precursor	1295-35-8	B115561	Bis(1,5-cyclooctadiene)nickel(0)	≥96%	A classical Ni(0) catalyst precursor; used to establish Ni-catalyzed cross-coupling systems and suitable for hard-to-activate substrates or Pd / Ni comparative development.
Common cocatalyst for Sonogashira	7681-65-4	C433811	Copper(I) iodide	Anhydrous, ≥99.995% metals basis	A classical Cu cocatalyst in Sonogashira systems; helps generate copper acetylide intermediates and improves coupling efficiency between haloheterocycles and terminal alkynes.
Common inorganic base (Suzuki / Sonogashira / C–O coupling)	584-08-7	P485463	Potassium carbonate	Anhydrous, premium pure, reagent grade, ≥99%	A commonly used mild inorganic base; promotes deprotonation and transmetalation in Suzuki–Miyaura, Sonogashira, and some C–O couplings, while remaining low-cost and broadly useful.
Common inorganic base (Suzuki / C–N / C–O coupling)	7778-53-2	P434005	Potassium phosphate tribasic	Anhydrous, ≥98%	Commonly used in Suzuki, Buchwald–Hartwig, and some C–O couplings; offers stable basicity and good compatibility, making it useful for condition screening with heterocyclic substrates.
Common inorganic base (higher-activity base)	534-17-8	C432848	Cesium carbonate	purum p.a., ≥98%(T)	A stronger, more soluble base; commonly used in optimizing more difficult couplings involving heterocyclic substrates, heteroaryl boron reagents, or C–N / C–O coupling.
Common strong base (C–N / C–O coupling)	865-48-5	S109392	Sodium tert-butoxide	≥98%	A strong-base additive; commonly used in Buchwald–Hartwig amination and some C–O couplings to improve deprotonation efficiency of amines or alcohols.
Pseudohalide-precursor activating reagent (Tf₂O)	358-23-6	T398957	Trifluoromethanesulfonic anhydride	≥99%	Commonly used to convert phenol, enol, and related sites into triflates and other pseudohalide entry points, thereby bringing non-halogenated substrates into subsequent cross-coupling routes.

Note: The products above are representative Aladdin offerings. For more product specifications, please refer to the product list at the end of the article or search the Aladdin website using the product name / CAS number / catalog number.

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