Wolff Rearrangement of Oxidatively Generated alpha-Oxo Gold Carbenes: An Effective Approach to Silylketenes

摘要

Gold-catalyzed oxidations of alkynes by N-oxides offer direct access to reactive alpha-oxo gold carbene intermediates from benign and readily available alkynes instead of hazardous diazo carbonyl compounds Despite various versatile synthetic methods developed based on this strategy, one of the hallmarks of alpha-oxo carbene/carbenoid chemistry, that is, the Wolff rearrangement, has not been realized in this context. This study discloses the first examples that show the Wolff rearrangement can be readily realized by alpha-oxo gold carbenes oxidatively generated from TBS-terminated alkynes (TBS = tert-butyldimethylsilyl). The thus-generated silylketenes can be either isolated pure or subsequently trapped by various internal or external nucleophiles in one pot to afford alpha-silylated carboxylic acids, their derivatives, or TBS-substituted allenes.