Phosphine‐Mediated Rauhut‐Currier‐Type/Acyl Transfer/Wittig Strategy for Synthesis of Spirocyclopenta[c]chromene‐Indolinones

Abstract

AbstractA phosphine‐mediated reaction for the construction of spirocyclopenta[c]chromene‐indolinones is reported via a Rauhut‐Currier (RC)‐type/acyl transfer/Wittig sequence. This methodology attributes the chemoselective phosphine addition to the alkynoate which generates the phosphorus zwitterion via RC‐type reaction, and that further undergoes O‐acylation to form the seven‐membered betaine intermediate with acyl chloride in the presence of base. Extensive investigations reveal that the exceptional δ‐acylation occurs through the C−O bond cleavage upon the seven‐membered betaine, and the subsequent Wittig reaction preferentially result in the aforementioned spiro compounds. Furthermore, our protocol could also be applicable to different alkynoates to provide a series of spirocyclopenta[c]chromenones bearing privileged skeletons.magnified image