Cyclizative dearomative rearrangement of pyridines with isocyanates

Abstract

Dearomatization of pyridines is a robust synthetic method to access aza-heterocycles. Simultaneously, intermolecular cyclizative rearrangement is a recently developed strategy for efficiently constructing tetrasubstituted carbons. Here, we show that an effective integration of the dearomatization approach with strategic cyclizative rearrangement enables 2-acyl-substituted pyridines and their analogues with common isocyanates to undergo a tandem [3 + 2] heteroannulation, followed by an extensive 1,2-carbon shift, thus providing a straightforward access to readily functionalized bicyclohydantoins. Based on the promotion of organophosphorus, we have shown for the first time that different types of migrating groups, such as ester, amide, aryl and trifluoromethyl groups, are all well-tolerated in the same reaction.