Ritter-Type Reactions in Organic Synthesis

Ritter‐type reactions represent a cornerstone of amide bond construction through the interception of carbocationic intermediates with nitriles. Traditionally catalysed by strong acids or Lewis acids, the classical pathway involves protonation or activation of an alcohol or alkene to generate a carbocation, which is then trapped by a nitrile to form an N-alkyl nitrilium ion. Subsequent hydrolysis furnishes the corresponding tertiary amide. The broad substrate scope, operational simplicity and compatibility with diverse nitriles have rendered the Ritter reaction a versatile tool for the synthesis of pharmaceuticals, agrochemicals and natural products. Recent advances have extended the methodology beyond conventional acid activation to encompass redox and photocatalytic strategies, enabling oxidative C–H functionalisation and selective amination of unactivated C–H bonds. These innovations have addressed longstanding challenges in atom economy, reaction selectivity and sustainability, while opening new avenues for late‐stage functionalisation of complex scaffolds. Moreover, the development of heterogeneous and supported Lewis acid catalysts has improved recyclability and process safety, aligning Ritter‐type amidations with modern green‐chemistry principles. Across academia and industry, ongoing work continues to refine mechanistic understanding, expand functional‐group tolerance and integrate Ritter‐type processes into multistep and flow protocols.

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Ritter-Type Reactions in Organic Synthesis publication trend

The graph below shows the total number of articles in ritter-type reactions in organic synthesis across all publications each year (not limited to Nature Index journals).

Technical terms

Carbocation: a positively charged carbon intermediate formed by loss of a leaving group or by electron transfer, central to the Ritter mechanism.

Nitrile: an organic functional group containing a carbon–nitrogen triple bond, serving as nitrogen source in Ritter reactions.

Lewis acid: an electron‐pair acceptor that activates substrates toward nucleophilic attack, often used to promote Ritter reactions.

Photocatalysis: the acceleration of a chemical reaction by light in the presence of a catalyst, enabling mild oxidative Ritter variants.

References

1. Organo-redox-catalysis for the difunctionalization of alkenes and oxidative Ritter reactions by C–H functionalization. Organic Chemistry Frontiers (2021).
2. Visible-light-mediated aerobic Ritter-type C–H amination of diarylmethanes using DDQ/ tert -butyl nitrite. Organic & Biomolecular Chemistry (2022).
3. Microwave Activation of the [FeCl3·6H2O–TsOH·H2O]-Catalyzed Reaction of Norbornene with Organic Nitriles. Russian Journal of Organic Chemistry (2024).