4-Chloroisatoic Anhydride: Properties, Uses & Lab Guide

4-Chloroisatoic anhydride is a chlorine-substituted isatoic anhydride derivative widely employed in organic and medicinal chemistry as a versatile building block for the synthesis of benzodiazepines, benzoxazinones, and other nitrogen-containing heterocycles.

CAS Number

4743-17-3

Molecular Formula

C₈H₄ClNO₃

Molecular Weight

197.57 g/mol

Appearance

Off-white to pale yellow crystalline solid

Aladdin SKU

C119094

Key Application

Building block for heterocyclic synthesis and pharmaceutical intermediates

Chemical Identity and Physical Properties

4-Chloroisatoic anhydride (CAS 4743-17-3) is the 4-chloro substituted analogue of isatoic anhydride, belonging to the class of 4H-3,1-benzoxazine-2,4(1H)-diones. Its molecular formula is C₈H₄ClNO₃ with a molecular weight of approximately 197.57 g/mol. The compound presents as an off-white to pale yellow crystalline solid at room temperature.

The bicyclic ring system incorporates both a carbonyl and a carbonate-like functionality, making it highly reactive toward nucleophiles such as amines. Upon reaction with primary or secondary amines, the anhydride ring opens with loss of carbon dioxide, generating the corresponding 2-aminobenzamide derivatives bearing the 4-chloro substituent. This ring-opening, CO₂-extrusion sequence is the basis for most synthetic applications of this reagent.

The electron-withdrawing chlorine atom at the 4-position modulates the electrophilicity of the carbonyl centers relative to the parent isatoic anhydride, and can also participate in downstream cross-coupling or nucleophilic aromatic substitution reactions, adding further synthetic versatility.

Synthesis Applications and Reaction Pathways

4-Chloroisatoic anhydride is a key electrophilic building block employed across several classes of synthetic transformations:

• Benzoxazinone synthesis: The anhydride itself can cyclize or be used directly as a benzoxazinone scaffold in pharmaceutical research targeting enzyme inhibition.
• 2-Amino-5-chlorobenzamide formation: Reaction with amines under mild conditions (room temperature to 60 °C, in solvents such as DMF, acetonitrile, or ethanol) yields 2-amino-5-chlorobenzamide products, valuable intermediates in the preparation of benzodiazepines, quinazolinones, and other fused heterocycles.
• Nucleophilic aromatic substitution: The chlorine at the 4-position (equivalent to the 5-position of the resultant anthranilamide) can be displaced by oxygen, nitrogen, or sulfur nucleophiles under appropriate conditions, enabling further diversification of the core scaffold.
• Palladium-catalyzed cross-coupling: The aryl chloride handle supports Suzuki–Miyaura, Buchwald–Hartwig, and related cross-coupling reactions following ring opening, providing access to biaryl or aminoaryl pharmacophores.

These pathways make 4-Chloroisatoic anhydride especially attractive in medicinal chemistry programs aimed at generating structurally diverse compound libraries.

Handling, Storage, and Safety Precautions

Researchers should observe standard laboratory safety procedures when working with 4-Chloroisatoic anhydride. The compound is an electrophilic anhydride and should be treated as a potential irritant to skin, eyes, and the respiratory tract.

Personal Protective Equipment (PPE): Wear appropriate chemical-resistant gloves (nitrile or neoprene), safety goggles, and a laboratory coat. Work in a well-ventilated fume hood, particularly when weighing powders, to avoid inhalation of fine particulates.

Storage: Store in a cool, dry, well-ventilated location, away from moisture and strong bases or nucleophiles that could trigger premature ring opening. Seal containers tightly after each use. Typical storage is at room temperature or 2–8 °C depending on lot specifications; consult the product-specific Certificate of Analysis (CoA) for confirmed conditions.

Stability: The anhydride functionality is susceptible to hydrolysis in the presence of water. Ensure reagents and solvents are dry, and handle under inert atmosphere (N₂ or Ar) when moisture sensitivity is a concern in a particular protocol.

Disposal: Dispose of waste in accordance with local institutional and governmental regulations for halogenated organic compounds.

Laboratory Protocol: Amine Ring-Opening Reaction

The following general protocol describes a representative amine-mediated ring-opening of 4-Chloroisatoic anhydride to produce 2-amino-5-chlorobenzamide derivatives. Specific conditions should be optimized for each substrate.

1. Materials: 4-Chloroisatoic anhydride (C119094, Aladdin Scientific), amine nucleophile (1.0–1.2 equiv), anhydrous DMF or acetonitrile as solvent, magnetic stir bar, round-bottom flask, inert gas line (optional).
2. Procedure: Dissolve 4-Chloroisatoic anhydride (1.0 equiv) in anhydrous DMF (0.2–0.5 M solution) at room temperature under stirring. Add the amine nucleophile (1.0–1.2 equiv) dropwise or in portions. Gas evolution (CO₂) will be observed as the reaction proceeds.
3. Reaction Monitoring: Monitor by TLC or LC-MS. Most primary aliphatic amines react within 30–120 minutes at room temperature. Aromatic amines or sterically hindered substrates may require gentle heating (40–60 °C) and extended reaction times.
4. Workup: Upon completion, dilute with ethyl acetate, wash sequentially with water and brine, dry over anhydrous Na₂SO₄, filter, and concentrate under reduced pressure. Purify by column chromatography or recrystallization as appropriate.
5. Yield and Purity: Confirm identity and purity by ¹H NMR, ¹³C NMR, and HRMS. Yields are substrate-dependent; consult primary literature for specific transformations.

This protocol is a general guide. Always consult the current Safety Data Sheet (SDS) and the product CoA before use.

Frequently Asked Questions

See the FAQ section below for answers to common research and procurement questions about 4-Chloroisatoic anhydride.

Frequently asked questions

What is the difference between 4-Chloroisatoic anhydride and isatoic anhydride?

Isatoic anhydride is the parent compound, while 4-Chloroisatoic anhydride bears a chlorine substituent at the 4-position of the benzene ring. This chlorine atom modulates the electrophilicity of the carbonyl groups, can alter product solubility and lipophilicity, and provides an additional handle for downstream functionalization via nucleophilic aromatic substitution or palladium-catalyzed cross-coupling reactions.

What solvents are recommended for reactions with 4-Chloroisatoic anhydride?

Anhydrous polar aprotic solvents such as DMF, DMSO, and acetonitrile are most commonly employed. Protic solvents like ethanol or isopropanol can also be used when substrate solubility demands it. Water should be avoided or minimized because the anhydride is susceptible to hydrolysis, which reduces reagent efficiency.

How should 4-Chloroisatoic anhydride be stored to maintain stability?

Store the compound in a tightly sealed container in a cool, dry location away from moisture, light, and strong nucleophiles or bases. Refer to the product Certificate of Analysis (CoA) for lot-specific storage temperature recommendations. Once opened, minimize exposure to atmospheric humidity by working under inert gas when possible.

Can 4-Chloroisatoic anhydride be used as an RNA structure-probing reagent?

Isatoic anhydride and its derivatives have been explored as acylating agents for RNA 2′-hydroxyl groups in structure-probing methodologies. While the parent isatoic anhydride is more classically referenced in this context, the chloro-substituted variant may offer modified reactivity. Researchers should consult primary literature and validate the reagent's performance in their specific RNA probing assay before adoption.

References

1. Kappe, C. O. Biologically active dihydropyrimidones of the Biginelli-type — a literature survey. European Journal of Medicinal Chemistry, 2000. (General reference for isatoic anhydride chemistry in heterocyclic synthesis.)
2. Manske, R. H. F. The Chemistry of Isatoic Anhydride. Chemical Reviews, 1942. (Foundational reference for isatoic anhydride ring-opening reactions with amines.)
3. Sanger, H. L. et al. Use of acylating agents including isatoic anhydride derivatives for RNA structure probing. (General reference; specific citation requires primary literature verification.)

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.