Divergent Synthesis of -Difluorinated Oxa-Spirocyclohexadienones by One-Pot Sequential Reactions of -Hydroxybenzyl Alcohols with Difluoroenoxysilanes.

A new efficient formal [2 + 3] cyclization of -hydroxybenzyl alcohols with difluoroenoxysilanes has been established. This convenient one-pot sequential procedure enables the divergent construction of highly functionalized -difluorinated oxa-spirocyclohexadienones under mild conditions. As opposed to the common C1 synthons in previous studies, difluoroenoxysilanes acted as new 3-atom (CCO) synthons for the first time here. The AcOH and HO generated in the reaction are critical for the reactions to proceed smoothly.