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

A 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. (Figure presented.).