Preparation of Furo[3,2-c]coumarins from 3-Cinnamoyl-4-hydroxy-2H-chromen-2-ones and Acyl Chlorides: A Bu3P-Mediated C-Acylation/Cyclization Sequence

A Bu3P‐mediated cyclization reaction of 3‐cinnamoyl‐4‐hydroxy‐2H‐chromen‐2‐ones though electrophilic addition of acyl chlorides towards the synthesis of highly functionalized furo[3,2‐c]coumarins bearing a phosphorus ylide moiety is described. These unprecedented cyclization reaction proceeds under mild reaction conditions within short reaction times (1 min to 1 h), and can be further applied in the synthesis of alkenyl‐substituted furo[3,2‐c]coumarins by the treatment with carbonyl electrophiles under basic conditions. Building rings: The preparation of furo[3,2‐c]coumarins with appending phosphorus ylides is realized through a Bu3P‐mediated cyclization reaction of 3‐cinnamoyl‐4‐hydroxy‐2H‐chromen‐2‐ones by electrophilic addition of acyl chlorides as the key step. These in situ generated ylide intermediates can efficiently react with carbonyl electrophiles to synthesize alkenyl‐substituted furo[3,2‐c]coumarins in moderate to high yields.