Microwave-accelerated Claisen rearrangements of allyl tetronates and tetramates

摘要

[3,3]Sigmatropic rearrangements of allyl tetronates and allyl tetramates to give 3-allyltetronic or -tetramic acids,respectively,proceed within 20-60 min under microwave irradiation (300 W,130-190 deg C).Consecutive (homo)sigmatropic [1,5]H-shifts such as oxa-ene reactions are promoted less effectively,which allows the isolation of Claisen intermediates of sigmatropic domino sequences,in contrast to conventional heating.