Cycloaddition von benzothiet an oxime, oximether und oximester

Benzothiete 1 generates by thermal ring opening an 8π electron system 2 which undergoes [8π + 2π] 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 .