(Alkylthio)- and (phenylthio)methoxycarbenes from oxadiazolines

Four 2-methoxy-5,5-dimethyl-Δ 3 -1,3,4-oxadiazolines bearing an alkylthio or arylthio group at C2 were prepared. The oxadiazolines undergo thermolysis at 60-80 °C in solution to afford the corresponding oxythiocarbene intermediates. In the absence of carbene traps, dimers of the carbenes were formed. The carbenes were trapped with ethyl crotonate, with dichloromaleic anhydride, with dimethyl acetylenedicarboxylate, and with phenyl isocyanate. Phenyl isocyanate traps methoxy(methylthio)carbene to form two types of adducts, both fundamentally different from the product obtained from reaction of dimethoxycarbene with phenyl isocyanate. All of the adducts have structures consistent with nucleophilic behaviour of the carbenes. Key words: oxythiocarbene, oxadiazoline, thermolysis, nucleophilic.