Copper(I)-carbenes as key intermediates in the [3 + 2]-cyclization of pyridine derivatives with alkenyldiazoacetates: a computational study

This work reports a computational study of the copper(I)-catalyzed regioselective synthesis of indolizine derivatives through the [3 + 2]-cyclization reaction of vinyldiazo acetates and pyridine derivatives. This reaction is predicted to proceed via a multi-step process with the initial decomposition of the diazo function and generation of an electrophilic copper(I) carbene intermediate. Subsequent attack of the pyridine derivative at the vinylogous position of the carbene would generate a vinylcuprate intermediate that would evolve to the final products through a sequence involving cyclization, reductive elimination, metal decoordination and final oxidative aromatization. According to our calculations, an alternative pathway involving the initial activation of the pyridine seems unlikely. These theoretical results could pave the way for further developments in vinyldiazo chemistry.