(ALKYLTHIO)METHOXYCARBENES AND (PHENYLTHIO)METHOXYCARBENES FROM OXADIAZOLINES

Four -methoxy-5,5-dimethyl-Delta(3)-1,3,4-oxadiazolines bearing an alk ylthio or arylthio group at C2 were prepared. The oxadiazolines underg o thermolysis at 60-80 degrees C in solution to afford the correspondi ng oxythiocarbene intermediates. In the absence of carbene traps, dime rs of the carbenes were formed. The carbenes were trapped with ethyl c rotonate, with dichloromaleic anhydride, with dimethyl acetylenedicarb oxylate, and with phenyl isocyanate. Phenyl isocyanate traps methoxy(m ethylthio)carbene to form two types of adducts, both fundamentally dif ferent from the product obtained from reaction of dimethoxycarbene wit h phenyl isocyanate. All of the adducts have structures consistent wit h nucleophilic behaviour of the carbenes.