The Wolff rearrangement is an important transformation to access ketenes via 1,2-alkyl or aryl migrations of α-diazoketones. In contrast, alkoxy group migration from free singlet carbenes has remained elusive owing to the intrinsically low migratory aptitude of alkoxy groups. Here we report a visible-light-induced 1,2-alkoxy/aryloxy shift of α-diazoacetates that generates oxy-substituted ketenes. These intermediates undergo efficient 2 + 2 cycloadditions with imines and nucleophilic addition reactions with amines. The method tolerates a wide substrate range, operates on gram scale, and is supported by mechanistic and computational studies. This work expands the scope of Wolff rearrangements and opens new chemical space for oxyketene reactivity.
Liu et al. (Thu,) studied this question.