Efficient Benzimidazolidinone Synthesis via Rhodium-Catalyzed Double-Decarbonylative C–C Activation/Cycloaddition between Isatins and Isocyanates

The
first decarbonylative cycloaddition of less-strained cyclic
ketones (isatins) with isocyanates is reported. Initiated by C–C
activation, this distinct [5 – 2 + 2] transformation provides
a rapid entry to access various benzimidazolidinone derivatives, and
a wide range of isocyanates can be efficiently coupled with broad
functional group tolerance. A modified one-pot process combining a
Curtius rearrangement and C–C activation was also achieved
by using acyl azides as the starting materials. A detailed mechanistic
study revealed a surprising double-decarbonylative reaction pathway.
The novel reactivity discovered in this basic research is expected
to shed light on the development of new heterocycle formation methods
through C–C/isocyanate coupling.