Facile Synthesis of Aza-Baylis-Hillman Adducts of Gycloalkenones:FeCl3-Mediated Direct Amination of Baylis-Hillman Alcohols

摘要

The Baylis-Hillman adducts of cycloalkenones have been used widely in organic synthesis.The synthesis of Baylis-Hillman adducts from the reaction of cycloalkenones and aldehydes has been carried out with a variety of catalyst system including the use of TMPDA~(2a) or DMAP.~(2b) However,the synthesis of aza-Baylis-Hillman adducts of cycloalkenones was not reported much.Direct synthesis of aza-Baylis-Hillman adducts from the reaction of cycloalkene-ones and N-tosylimines was examined by using DMAP~(3a,b) or N-heterocyclic carbene catalyst very recently.However,the methods suffer from low yields of products~(3a,b) and the use of special catalyst.In addition,these direct methods require the preparation of N-tosylimines,which could be hydrolyzed to some extent into the corresponding aldehydes and tosylamide during the separation of N-tosylimine and during the next Baylis-Hillman reaction,and this makes the separation of product tedious and lowers the yield.