Transposition of an acrylate moiety in TMSOTf-mediated reaction of alkynyl vinylogous carbonates gives heterocyclic dienes

TMSOTf-mediated reaction of alkynyl vinylogous carbonates serendipitously gave 1,4-oxazepine and dihydropyran dienes via transposition of an ethyl acrylate moiety involving intramolecular cascade Prins-type cyclization/retro-oxa-Michael reaction/cycloisomerisation. The developed atom-economical protocol selectively provides an E double bond geometry. Dihydropyran dienes could be reduced diastereoselectively using Et3SiH/TMSOTf or could be transformed into polycyclic heterocycles by Heck reaction.

Automated summary

The TMSOTf-mediated reaction of alkynyl vinylogous carbonates unexpectedly generates 1,4-oxazepine and dihydropyran dienes through the transposition of an ethyl acrylate moiety via an intramolecular cascade Prins-type cyclization/retro-oxa-Michael reaction/cycloisomerisation. This atom-economical protocol selectively produces a specific E double bond geometry, and the dihydropyran dienes can be further transformed into polycyclic heterocycles using the Heck reaction.