Activation of Cyanate Anions by Phosphine Radical Cations Enables Formal Hydrocarbamoylation of Alkenes

TL;DR

A new photocatalytic method uses cyanate anions to create N-acyl iminophosphorane products from alkenes through radical chemistry.

Contribution

The study introduces a redox-neutral formal hydrocarbamoylation strategy using phosphine radical cations and cyanate anions.

Findings

The phosphoranyl radical is generated by adding cyanate anion to a phosphine radical cation.

The method works on diverse alkenes with sensitive functional groups.

N-acyl iminophosphorane products can be converted to other nitrogen-containing functional groups.

Abstract

Catalytic methods that enable functionalization of alkenes with radical intermediates generated from common feedstock chemicals are valuable in synthetic chemistry. In this study, we disclose a photocatalytic formal hydrocarbamoylation strategy for preparation of N‐acyl iminophosphorane products from activated alkenes through isocyanate‐derived phosphoranyl radicals. Mechanistic investigations suggest generation of the phosphoranyl radical by addition of a cyanate anion to a phosphine radical cation and provide support for its reactivity through the isocyanate moiety. This redox‐neutral method enables hydrofunctionalization of diverse alkenylarene and electron‐deficient alkene substrates containing sensitive groups such as epoxide, unactivated alkene, amine, or electron‐rich and electron‐deficient heterocycles. The synthetic versatility of the N‐acyl iminophosphorane functionality is demonstrated through one‐step conversion to other valuable nitrogen‐containing functional groups.

A photocatalytic formal hydrocarbamoylation reaction that employs a cyanate anion as the C1 source and provides N‐acyl iminophosphorane products from activated alkenes is described. Mechanistic investigations suggest generation of a phosphoranyl radical by addition of the cyanate anion to a phosphine radical cation, which enables the delivery of the carbamoyl group across alkenes.

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