Experimental Selection Logic for Phase-Transfer Catalysts: Choosing Catalysts by Phase-State System, Source of Anionic Species, and Reaction Task

1. What Is a Phase-Transfer Catalyst

 

Phase-transfer catalysis (PTC) refers to the use of a small amount of catalyst in two immiscible phases, or in a multiphase system composed of a solid and a liquid, to transfer one reactant from its original phase into another phase so that the reaction can proceed more rapidly. The transferred reactant is most commonly an anion. Common phase-transfer catalysts include onium salts such as quaternary ammonium salts and quaternary phosphonium salts, as well as ligand-type catalysts capable of complexing inorganic cations, such as crown ethers.

 

The purpose of phase-transfer catalysis is not to "dissolve all materials into a single phase," but to solve two more specific problems. First, reactants in different phases have insufficient contact with each other, so the reaction rate is limited by the interface. Second, inorganic salts, inorganic bases, or the ionic reactive species generated from them cannot readily enter the phase in which the organic reaction is more likely to occur. The role of a phase-transfer catalyst is to connect "interphase transfer" with "chemical reaction."

 

2. What Phase-Transfer Catalysts Do in Reactions

 

The two most common modes of action in phase-transfer catalysis are as follows.

 

The first is anion transfer. Onium salts such as quaternary ammonium salts and quaternary phosphonium salts first undergo ion exchange with anions in the aqueous phase or solid phase, carrying the anions into the organic phase. Once in the organic phase, the anions then react with the organic substrate. Starks's classic 1971 work dealt precisely with this type of anion-transfer reaction mediated by quaternary ammonium and phosphonium salts.

 

The second is cation complexation. When the main limitation is not that the anion cannot enter the organic phase, but rather that alkali metal cations such as sodium and potassium are strongly ion-paired with the anion, crown ethers can complex these cations, weaken ion pairing, and thereby increase the nucleophilicity or basicity of the corresponding anion in the organic phase. The key role of crown ether catalysts is to complex alkali metal cations and modulate the ion-pair state; the key role of onium-salt catalysts is to form organic-phase-soluble ion pairs through ion exchange and transfer the anion into the organic phase to participate in the reaction.

 

For systems such as active methylene compounds and glycine Schiff bases, which must first undergo deprotonation before reacting, the process can often be understood in terms of an interfacial mechanism: the substrate first forms an anionic species paired with a metal cation near the interface, and the catalyst then converts it into an onium ion pair in the organic phase.

 

3. First Judge Whether Phase-Transfer Catalysis Is Needed Based on the Phase-State System

 

Phase-transfer catalysis is mainly used in liquid-liquid biphasic systems and solid-liquid multiphase systems. If the substrate is in the organic phase and the inorganic base or inorganic salt is in the aqueous phase, or if the inorganic base or inorganic salt is present as a solid, and the reaction depends on anion transfer or interfacial deprotonation, then phase-transfer catalysis should be considered. If the reaction is already a stable homogeneous system, whether to use phase-transfer catalysis is usually not the first issue to address.

 

System State	Common Situation	Whether Phase-Transfer Catalysis Should Be Prioritized	Explanation
Liquid-liquid biphasic	Organic substrate in the organic phase; inorganic base or inorganic salt in the aqueous phase	Worth prioritizing for evaluation	This is a typical phase-transfer catalysis scenario
Solid-liquid multiphase	Organic substrate dissolved in an organic solvent; inorganic base or inorganic salt present as a solid	Worth prioritizing for evaluation	Crown ethers and onium salts are both common in this type of system
Already homogeneous	Substrate, base, and nucleophile all react stably in a single phase	Generally not the first choice	In this case, the bottleneck is often not interphase transfer
Substrate is clearly sensitive to water or to a strong-base interface	Prone to hydrolysis, decomposition, or racemization	Small-scale feasibility testing is needed first	The multiphase conditions themselves may introduce side reactions before the desired reaction proceeds

 

4. Select the Catalyst Type According to the Source of the Anionic Species

 

When selecting a phase-transfer catalyst, the first step is to determine how the bond-forming anionic species in the reaction is generated. If the anion is supplied directly by an inorganic salt, the key issue is transferring the anion from the aqueous phase or solid phase into the organic phase. If the anion is generated in situ from the substrate under the action of an inorganic base, the key issues are interfacial deprotonation and its subsequent transfer. If the reaction is limited by strong ion pairing between alkali metal cations and anions, cation-complexing catalysts should be considered first.

 

Source of the Anionic Species	Catalyst Type to Prioritize	Main Function
The anion is supplied directly by an inorganic salt	Onium-salt-type phase-transfer catalyst	Transfer the anion from the aqueous phase or solid phase into the organic phase
The anion is generated in situ by deprotonation of the substrate	Onium-salt-type phase-transfer catalyst, often combined with a biphasic inorganic base system	Promote entry of the ion species formed after interfacial deprotonation into the organic phase for reaction
The reaction is limited by strong ion pairing between alkali metal cations and anions	Cation-complexing catalysts such as crown ethers	Complex alkali metal cations, alter the ion-pair state, and increase the reactivity of the anion in the organic phase
Both interphase reaction and enantioselective control are required	Chiral quaternary ammonium phase-transfer catalyst	Form a chiral onium ion pair and control the asymmetric reaction process

 

For systems in which the anion is supplied directly by an inorganic salt, the key selection criterion is whether the anion can efficiently enter the organic phase. For systems in which the anion is generated in situ from the substrate, the key criterion is whether interfacial generation and subsequent transfer are properly matched. For systems in which ion pairing with alkali metal salts is strong, the key criterion is whether the cation-complexing ability is sufficient to alter the ion-pairing state.

 

5. Understand Common Selection Strategies by Reaction Task

 

5.1 Anionic Nucleophilic Substitution, Etherification, and Thioetherification

 

These reactions are commonly encountered in systems where the organic substrate is in the organic phase and the inorganic anion is in the aqueous phase or solid phase. Whether the reaction proceeds smoothly depends on whether the anion can effectively enter the organic phase, so onium-salt-type phase-transfer catalysts are usually considered first. During condition screening for such systems, the source of the inorganic salt, the amount of water, the phase ratio, and the stirring conditions should all be examined together. If interfacial transfer is insufficient, both the reaction rate and reproducibility can be significantly affected even when a catalyst is present.

 

5.2 Active Methylene Compounds, Carbonyl α-Positions, and Related Alkylation Reactions

 

In these reactions, the key step is usually that the substrate is first deprotonated by an inorganic base to generate an anionic species, which is then converted by the phase-transfer catalyst into an onium ion pair in the organic phase and continues reacting there. The Makosza interfacial mechanism and its later developments provide an important mechanistic basis for understanding this type of system.

 

In such systems, base strength, interfacial area, the mode of electrophile addition, and catalyst hydrophobicity can all affect the outcome. In systems that depend on interfacial deprotonation and ion exchange, excessively high lipophilicity of the catalyst may be unfavorable for its function at the interface. Under strongly basic conditions, the onium intermediates or even the catalyst itself may undergo decomposition, such as Hofmann elimination, nucleophilic substitution, or Stevens rearrangement.

 

5.3 Asymmetric Phase-Transfer Catalysis

 

In asymmetric phase-transfer catalysis (APTC), the asymmetric alkylation of glycine Schiff bases and related substrates catalyzed by chiral quaternary ammonium salts is a representative system for constructing chiral α-amino acid derivatives. Reviews in this field have long treated this direction as a core topic in chiral phase-transfer catalysis.

 

In addition to interphase transfer, these reactions require simultaneous control over chiral ion-pair formation, enantioselectivity, racemization, and overreaction. Therefore, the choice of chiral phase-transfer catalyst must be considered together with substrate structure, base type, temperature, and phase composition.

 

6. Key Experimental Conditions That Affect the Outcome

 

The outcome of phase-transfer catalysis is often determined jointly by the phase-state system, the base, and mass transfer. Interfacial area, base strength, catalyst hydrophobicity, and the amount of water are all key factors that directly influence the result.

 

Variable	Main Influence
Stirring intensity and interfacial area	Affect the efficiency of interphase contact and transfer
Amount of water and phase ratio	Affect the state of the inorganic base, phase distribution, and side reactions
Type and strength of inorganic base	Affect deprotonation efficiency and the tendency toward side reactions
Catalyst hydrophobicity	Affect its distribution between the interface and the organic phase
Temperature	Affects mass transfer, ion exchange, and equilibrium, and also influences side reactions
Catalyst loading	Affects the rate of interphase transfer, but cannot replace optimization of phase-state and base conditions

 

Therefore, a safer and more practical experimental sequence is usually: first determine the phase-state system and the inorganic base system, and then compare catalysts; first ensure that the system can establish an effective interphase reaction, and only then further pursue higher conversion or better selectivity.

 

7. Screening Sequence for Phase-Transfer Catalysts

 

(1) First determine whether the reaction is suitable for phase-transfer catalysis screening.

 

When a reaction is limited by interphase transfer, interfacial deprotonation, or ion pairing of alkali metal salts in a liquid-liquid biphasic or solid-liquid multiphase system, phase-transfer catalysis can be considered. If the reaction already proceeds stably in a homogeneous system, phase-transfer catalysis is usually not treated as the priority direction for optimization. For substrates and intermediates that are clearly sensitive to water, strong base, or the interfacial environment, small-scale feasibility testing should be carried out first.

 

(2) Then determine how the anionic species involved in the reaction is generated.

 

If the anion is supplied directly by an inorganic salt, onium-salt-type phase-transfer catalysts should be considered first. If the anion is generated in situ from the substrate under the action of an inorganic base, the focus should be on interfacial deprotonation and subsequent ion-pair transfer. If the reaction is limited by ion pairing between alkali metal cations and anions, cation-complexing catalysts such as crown ethers should be prioritized.

 

(3) First determine the broad catalyst class, and then compare specific structures within that class.

 

For most phase-transfer catalytic reactions, the first choice is made among broad classes such as quaternary ammonium salts, quaternary phosphonium salts, crown ethers, or chiral quaternary ammonium salts, and only then are structural differences among catalysts within the same class compared.

 

(4) After fixing the phase-state system and base system, carry out small-scale catalyst screening and assess mass-transfer factors in light of the results.

 

During screening, one organic phase and one inorganic base system should be fixed first, and catalyst structures should then be compared. If scale-up leads to severe emulsification, difficult phase separation, or results that are highly sensitive to stirring conditions, the phase-state system, interface, and mass-transfer conditions should be re-examined rather than attributing the problem only to catalyst structure itself.

 

(5) After determining the catalyst direction, then optimize the amount of water, phase ratio, stirring, temperature, and catalyst loading.

 

This sequence helps distinguish the respective effects of catalyst selection and condition optimization on the reaction outcome.

 

8. Navigation Table of Representative Chemicals Related to Phase-Transfer Catalysts (Choose Table 1 to Table 5 by Research or Experimental Objective)

 

Research or Experimental Objective	Recommended Table to Consult First	Why Start with This Table	Recommended Related Table(s)	Navigation Notes
Establish an initial screening system for conventional liquid-liquid biphasic phase-transfer catalytic reactions	Table 1	Quaternary ammonium phase-transfer catalysts are the most common starting point and have broad applicability, making them suitable for first assessing whether the system shows a clear phase-transfer-promoting effect	Table 5	Suitable for initial catalyst screening in conventional multiphase reactions such as etherification, alkylation, and nucleophilic substitution, followed by adjustment of the phase-state system and reactivity in combination with inorganic bases and inorganic salts
Screen solid-liquid multiphase reactions, or compare the effects of different quaternary ammonium salt structures on the reaction	Table 1	Table 1 includes tetraalkylammonium salts, benzyl quaternary ammonium salts, and long-chain quaternary ammonium salts, making it suitable for comparing differences in ion-transfer ability and compatibility with the organic phase	Table 5	Suitable for systems in which the substrate is in the organic phase and the inorganic salt or inorganic base is present in solid form; screening should also consider base type, salt source, and stirring conditions
Compare differences between quaternary ammonium and quaternary phosphonium onium catalysts in the same reaction	Table 2	Table 2 focuses on quaternary phosphonium phase-transfer catalysts and is suitable for parallel comparison with the quaternary ammonium salts in Table 1	Tables 1 and 5	Suitable for comparing the effects of different onium centers on conversion, phase distribution, and side reactions under the same substrate, the same base, and the same phase-state system
The substrate is relatively hydrophobic, or there is a need to examine the performance of highly lipophilic onium catalysts in the organic phase	Table 1	Table 1 contains long-chain quaternary ammonium salts and benzyl quaternary ammonium salts, making it suitable for first evaluating catalyst lipophilicity and compatibility with the organic phase	Tables 2 and 5	When ordinary tetrabutylammonium salts perform only moderately, Table 2 can be further consulted to examine long-chain quaternary phosphonium salts, while Table 5 can be used to adjust the source of the base and salt
The reaction involves inorganic salts such as potassium salts or sodium salts, and the key issue is cation association rather than simple anion transfer	Table 3	Crown ethers and cryptands change the ion-pair state by complexing alkali metal cations, making them suitable for this type of problem	Table 5	Suitable for solid-liquid systems or nearly anhydrous systems involving salts such as potassium fluoride, potassium iodide, potassium bromide, potassium carbonate, and cesium carbonate; the salt type should be considered together with the complexing agent
Conduct research on nucleophilic fluorination, anhydrous nucleophilic substitution, or systems requiring enhanced reactivity of alkali metal salts in the organic phase	Table 3	Crown ethers and cryptands are key additives in such systems and can help alkali metal salts exhibit reactivity in the organic phase	Table 5	In such experiments, the complexing agent should usually be evaluated together with matched base/salt components such as potassium fluoride, potassium carbonate, and cesium carbonate, rather than screening the complexing agent alone
Carry out research on asymmetric phase-transfer catalysis, such as alkylation of glycine Schiff bases or reactions controlled by chiral ion pairs	Table 4	Table 4 focuses on cinchona alkaloid parent structures and chiral phase-transfer catalysts and is the core product table for entering chiral screening	Table 5	Suitable for first determining the chiral catalyst scaffold, then adjusting enantioselectivity and chemoselectivity in combination with inorganic base strength, phase composition, and substrate type
Plan to design or expand the structure of chiral phase-transfer catalysts starting from cinchona alkaloids	Table 4	Table 4 includes both directly usable chiral phase-transfer catalysts and cinchona alkaloid parent structures for derivatization design	Table 5	Suitable for catalyst structure modification, chiral source screening, and development of asymmetric catalytic routes; it can also be used to compare the effects of different cinchona scaffolds on the reaction outcome
First determine whether a phase-transfer catalytic system suffers from a "catalyst problem" or from a "base and salt condition problem"	Table 5	Inorganic bases and inorganic salts determine the anion source, deprotonation ability, and phase-state conditions, and form the basis for defining the operating limits of the system	Tables 1, 2, and 3	When the reaction fails to start, shows unstable conversion, or gives poor reproducibility, it is advisable to first revisit Table 5 and then decide whether to continue screening quaternary ammonium salts, quaternary phosphonium salts, or crown ethers/cryptands
Use one set of products to carry out the initial screening for "conventional phase-transfer catalytic method development"	Table 1	Table 1 is suitable as the first entry point for conventional method development, allowing an initial judgment as to whether there is a clear phase-transfer-promoting effect	Tables 5 and 3	It is recommended to use Table 1 first to establish a basic biphasic system; if the issue shifts to alkali metal salt complexation, then consult Table 3; if the problem lies in the base or salt source, return to Table 5 for adjustment

 

Table 1 | Quaternary Ammonium Phase-Transfer Catalysts

 

Classification	CAS No.	Aladdin Catalog No.	Name	Grade or Purity	Product Features and Applications
Tetraalkylammonium phase-transfer catalyst	32503-27-8	T432627	Tetrabutylammonium hydrogensulfate (TBAHS)	Anhydrous grade, ≥97%	A classic liquid-liquid biphasic phase-transfer catalyst, commonly used in etherification, alkylation, carboxylate O-alkylation to esters, and nucleophilic substitution reactions involving an aqueous inorganic base phase
Tetraalkylammonium phase-transfer catalyst	1941-30-6	T119590	Tetrapropylammonium bromide	Ion-pair chromatography grade, ≥99% (AT)	A tetraalkylammonium-type ion-transfer reagent for screening anion transfer, halide exchange, and nucleophilic substitution conditions in solid-liquid or liquid-liquid systems
Tetraalkylammonium phase-transfer catalyst	1112-67-0	T101035	Tetrabutylammonium chloride	Ion-pair chromatography grade, ≥99%	A commonly used quaternary ammonium phase-transfer catalyst for alkyl halide substitution, etherification, and ion-transfer reactions under multiphase basic conditions
Tetraalkylammonium phase-transfer catalyst	1643-19-2	T103374	Tetrabutylammonium bromide	Ion-pair chromatography grade, ≥99%	Commonly used in solid-liquid and liquid-liquid phase-transfer catalytic systems, suitable for initial screening of alkylation, condensation, carboxylate O-alkylation to esters, and general anionic nucleophilic reactions
Tetraalkylammonium phase-transfer catalyst	311-28-4	T103715	Tetrabutylammonium iodide (TBAI)	Ion-pair chromatography grade	Combines phase-transfer capability with iodide introduction and is commonly used in multiphase systems for halide exchange, nucleophilic substitution, and improving substrate reactivity through in situ iodide exchange
Benzyl quaternary ammonium phase-transfer catalyst	56-37-1	B108417	Benzyltriethylammonium chloride	≥98%	A classic benzyl quaternary ammonium phase-transfer catalyst, commonly used in etherification, alkylation, and nucleophilic substitution reactions involving an aqueous inorganic base phase
Benzyl quaternary ammonium phase-transfer catalyst	23616-79-7	B102662	Benzyltributylammonium chloride (BTBAC)	≥98%	More lipophilic and suitable for biphasic systems with relatively hydrophobic substrates in the organic phase; can be used in halide transformation, etherification, and anion-transfer reactions
Long-chain quaternary ammonium phase-transfer catalyst	5137-55-3	M106664	Methyltrioctylammonium chloride	≥97%	A long-chain, highly lipophilic quaternary ammonium salt suitable for anion transfer in hydrophobic organic phases and for multiphase reaction systems involving strongly hydrophobic substrates

 

Table 2 | Quaternary Phosphonium Phase-Transfer Catalysts

 

Classification	CAS No.	Aladdin Catalog No.	Name	Grade or Purity	Product Features and Applications
Tetraalkylphosphonium phase-transfer catalyst	3115-68-2	T107471	Tetrabutylphosphonium bromide	≥98%	A quaternary phosphonium phase-transfer catalyst for multiphase anion transfer, nucleophilic substitution, and screening studies comparing quaternary ammonium and quaternary phosphonium salts
Tetraalkylphosphonium phase-transfer catalyst	2304-30-5	T101355	Tetrabutylphosphonium chloride	≥96%	Commonly used in comparative studies of phase-transfer catalytic methods and ion-transfer behavior; can serve as a catalyst candidate for multiphase nucleophilic reactions and biphasic basic systems
Long-chain quaternary phosphonium phase-transfer catalyst	14937-45-2	T162757	Tributylhexadecylphosphonium Bromide	≥98% (T)	Combines a quaternary phosphonium center with a long-chain lipophilic structure, making it suitable for ion transfer in hydrophobic organic phases and for multiphase reaction systems involving highly lipophilic substrates

 

Table 3 | Crown Ether-, Benzo-Crown Ether-, and Cryptand-Type Complexing Phase-Transfer Catalysts

 

Classification	CAS No.	Aladdin Catalog No.	Name	Grade or Purity	Product Features and Applications
Crown ether complexing phase-transfer catalyst	17455-13-9	C124569	18-Crown-6	Ion-pair chromatography grade, ≥99% (GC)	A classic potassium-ion complexing agent, commonly used with potassium salts in solid-liquid phase-transfer catalysis, fluorination, etherification, and nucleophilic substitution reactions
Crown ether complexing phase-transfer catalyst	33100-27-5	C105798	15-Crown-5	≥97%	Commonly used to complex sodium ions and suitable for research on multiphase nucleophilic reactions, ion transfer, and solubility improvement involving sodium salts
Benzo-crown ether complexing phase-transfer catalyst	14098-44-3	B111880	Benzo-15-crown-5	≥98%	Possesses both an aromatic framework and cation-complexing ability, and can be used in sodium-salt-related phase-transfer systems and ion-recognition-type reaction studies
Crown ether complexing phase-transfer catalyst	16069-36-6	D119931	Dicyclohexano-18-crown-6	≥98%	Has good solubility in the organic phase and is commonly used in solid-liquid phase-transfer catalysis involving potassium salts, anhydrous nucleophilic substitution, and ion-pair modulation systems
Benzo-crown ether complexing phase-transfer catalyst	14187-32-7	D102033	Dibenzo-18-crown-6	≥98%	An aromatic crown ether complexing agent commonly used for alkali metal salt phase transfer, cation complexation, and modulation of ionic reactivity in multiphase systems
Macrocyclic crown ether complexing phase-transfer catalyst	14174-09-5	D154617	Dibenzo-24-crown 8-Ether	≥98%	The larger macrocyclic cavity favors complexation of larger guest ions and can be used in phase-transfer-related studies of ion recognition, host-guest interactions, and macrocyclic coordination
Cryptand-type complexing phase-transfer catalyst	23978-09-8	H119933	4,7,13,16,21,24-Hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane	≥98%	A strong cation-complexing agent commonly used with alkali metal salts in anhydrous multiphase systems for nucleophilic substitution, fluorination, and construction of highly reactive anionic systems

 

Table 4 | Cinchona Alkaloid Parent Structures and Chiral Phase-Transfer Catalysts

 

Classification	CAS No.	Aladdin Catalog No.	Name	Grade or Purity	Product Features and Applications
Cinchona alkaloid parent structure	118-10-5	C106926	(+)-Cinchonine	Moligand™, ≥98%	A cinchona alkaloid scaffold compound commonly used as a parent structure for quaternary ammonium chiral phase-transfer catalysts and also for studies on chiral catalyst structure modification
Cinchona alkaloid parent structure	56-54-2	Q109702	Quinidine	Moligand™, ≥98%, contains 5-15% Dihydroquinidine	A commonly used chiral source based on cinchona alkaloids, suitable for constructing quaternary ammonium chiral phase-transfer catalysts and asymmetric alkylation catalytic systems
Cinchona alkaloid parent structure	485-71-2	C109632	Cinchonidine	Moligand™, ≥98%	A representative cinchona alkaloid scaffold commonly used for preparing chiral phase-transfer catalysts and for enantioselective condition screening
Cinchona alkaloid parent structure	130-95-0	Q105031	Quinine	Moligand™, ≥97%	A common chiral natural-product scaffold that can serve as a starting structural unit for chiral phase-transfer catalysts, chiral bases, or systems related to chiral recognition
Chiral phase-transfer catalyst	69221-14-3	B120854	N-Benzylcinchoninium Chloride [Chiral Phase-Transfer Catalyst]	≥99%	A directly usable quaternary ammonium chiral phase-transfer catalyst commonly used in asymmetric alkylation, transformation of glycine Schiff base derivatives, and enantioselectivity screening
Chiral phase-transfer catalyst	200132-54-3	O302704	O-Allyl-1-(anthracen-9-ylmethyl)cinchonidinium bromide	≥95%	A cinchona-alkaloid-derived chiral quaternary ammonium salt commonly used in highly selective asymmetric phase-transfer catalytic reactions and studies on chiral ion-pair control

 

Table 5 | Common Supporting Inorganic Bases and Inorganic Salts Used in Phase-Transfer Catalysis

 

Classification	CAS No.	Aladdin Catalog No.	Name	Grade or Purity	Product Features and Applications
Halide source / supporting inorganic salt	7758-02-3	P433933	Potassium bromide	Anhydrous grade, high purity, reagent grade, ≥99%	Commonly used as a bromide source in halide exchange and nucleophilic substitution reactions, and also in studies of anion transfer under phase-transfer catalytic conditions
Halide source / supporting inorganic salt	7681-11-0	P433793	Potassium iodide	Anhydrous grade, high purity, reagent grade, ≥99%	Commonly used in halide exchange, nucleophilic substitution involving iodide, and phase-transfer catalytic systems related to leaving-group activation
Strong base / supporting inorganic base	1310-73-2	S431793	Sodium hydroxide	Anhydrous grade, ≥98%, pellets	A classic strong base for biphasic systems, commonly used to generate anionic nucleophiles and promote etherification and alkylation; a common supporting base in liquid-liquid phase-transfer catalysis
Halide source / supporting inorganic salt	7789-23-3	P434124	Potassium fluoride	Suitable for analysis, ACS, guaranteed reagent grade	Commonly used with crown ethers or cryptands in nucleophilic fluorination, alkyl halide transformation, and anhydrous multiphase nucleophilic substitution reactions
Strong base / supporting inorganic base	1310-58-3	P112281	Potassium hydroxide	Electronic grade, ≥99.99% metals basis, excluding sodium	Commonly used in deprotonation, etherification, alkylation, and other reactions requiring interfacial basic activation in strongly basic biphasic systems
Medium-strong base / supporting inorganic base	534-17-8	C432848	Cesium carbonate	purum p.a., ≥98% (T)	Commonly used in relatively mild deprotonation and solid-liquid multiphase systems; can be combined with crown ethers or phase-transfer catalysts for etherification, alkylation, and condensation reactions
Medium-strong base / supporting inorganic base	584-08-7	P111556	Potassium carbonate	AR, ≥99%	A commonly used mild inorganic base in phase-transfer catalysis, suitable in solid-liquid systems for etherification, carboxylate generation and subsequent O-alkylation to esters, alkylation, and general anion-generation steps

 

Note: The products above are representative products from Aladdin. For more product specifications, search by "product name/CAS/catalog number" on the Aladdin website.

 

References

 

[1] International Union of Pure and Applied Chemistry. phase-transfer catalysis. In: Compendium of Chemical Terminology, 5th ed. 2025. DOI: 10.1351/goldbook.P04536.

 

[2] Starks C M. Phase-transfer catalysis. I. Heterogeneous reactions involving anion transfer by quaternary ammonium and phosphonium salts[J]. Journal of the American Chemical Society, 1971, 93(1): 195-199. DOI: 10.1021/ja00730a033.

 

[3] Starks C M, Liotta C L, Halpern M. Phase-Transfer Catalysis: Fundamentals, Applications, and Industrial Perspectives[M]. Dordrecht: Springer, 1994. DOI: 10.1007/978-94-011-0687-0.

 

[4] Naik S D, Doraiswamy L K. Phase transfer catalysis: Chemistry and engineering[J]. AIChE Journal, 1998, 44(3): 612-646. DOI: 10.1002/aic.690440312.

 

[5] Makosza M. Phase-transfer catalysis. A general green methodology in organic synthesis[J]. Pure and Applied Chemistry, 2000, 72(7): 1399-1403. DOI: 10.1351/pac200072071399.

 

[6] Ooi T, Maruoka K. Recent advances in asymmetric phase-transfer catalysis[J]. Angewandte Chemie International Edition, 2007, 46(23): 4222-4266. DOI: 10.1002/anie.200601737.

 

[7] Hashimoto T, Maruoka K. Recent development and application of chiral phase-transfer catalysts[J]. Chemical Reviews, 2007, 107(12): 5656-5682. DOI: 10.1021/cr068368n.

 

[8] Lee H J, Maruoka K. Asymmetric phase-transfer catalysis[J]. Nature Reviews Chemistry, 2024, 8(11): 851-869. DOI: 10.1038/s41570-024-00642-x.

 

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Cinchona Alkaloid Chiral Toolbox: Selection & Troubleshooting from Pseudoenantiomer Switching to PTC/Sharpless AD/Chiral Resolution (including Product Tables A–D)