CYCLOADDITION OF BENZOTHIETE TO OXIMES, OXIME ETHERS AND OXIME ESTERS

Benzothiete 1 generates by thermal ring opening an 8-pi-electron system 2 which undergoes [8-pi + 2-pi] cycloaddition reactions with the oxime systems 3a-g. In accordance with the FMO theory the 1,3-thiazine derivatives 4a-g are formed in a regiospecific and 4f additionally in a stereospecific manner. The O-acylated adducts 4h-j enter the same cycloaddition; however, an elimination reaction 4 --> 5, 6 can provoke the addition of a second benzothiete, yielding the tetracyclic compounds 7j, and 8i,j.