PHOTOLYTIC FORMATION OF NITRILE SULFIDES FROM FIVE-MEMBERED HETEROCYCLIC-COMPOUNDS

A number of phenyl-substituted five-membered heterocyclic compounds containing C, N, and S atoms have been examined for the possibility of their photolytic formation of benzonitrile sulphide. The latter is thermally unstable, giving rise to benzonitrile and sulphur, but in neat dimethyl acetylenedicarboxylate the cycloaddition product (20) is formed: this is considered to be strong evidence for photolytic formation of benzonitrile sulphide. The yield of (20) obtained from compounds (1)-(12) was 5-21%, depending on the individual heterocyclic compound. Ready photolytic fragmentation of the heterocyclic compounds with formation of nitrile sulphide apparently takes place when extrusion of a small inorganic fragment (CO, CO 2, COS, CS2, or N2, etc.) is possible, a process which appears to be general for this type of compound.