Thermal Ene Reactions of 3-(Alk-2-enyl)benzylamino-2-(methoxycarbonyl)acrolein Derivatives Leading to 4,5-Dihydro-1H-azepines

Thermal reaction of 3-(alk-2-enyl)benzylamino-2-(methoxycarbonyl)acrolein derivatives 3 gave 4,5-dihydro-1H-azepines 4 stereoselectively in good yields via an intramolecular carbonyl-ene reaction. Conjugated diene compounds 10 from acroleins 3 also underwent olefin-ene reaction to give azepine derivatives 11. In these azepine-ring formation, the methoxycarbonyl group at the 2-position in 3 facilitated the progress of the reaction more effectively than the cyano group previously reported by us.