Studies of heterocyclic compounds. Part 29. The formation and reactions of 5-(2-chlorovinyl)-2-phenyl-1,2,3-thiadiazolylium salts: routes to 6aλ4-thia-1,2,6-triazapentalenes and 6aλ4-thia-6-selena-1,2-diazapentalenes

Abstract

The reaction of 3,4-dimethyl-1-phenyl-6-oxa-6aλ⁴-thia-1,2-diazapentalene and 6,7-dihydro-2-phenyl-5H-3-oxa-2aλ⁴-thia-1,2-diazacyclopent[cd]indene with phosphoryl chloride in dimethylformamide or 1,2-dichloroethane gave respectively 4-methyl-5-(1-methyl-2-chlorovinyl)-2-phenyl-1,2,3-thiadiazolylium phosphorodichloridate and 7-chloromethylene-4,5,6,7-tetrahydro-2-phenylbenz[d][1,2,3]thiadiazolylium phosphorodichloridate as oils which, with perchloric acid, afford the corresponding stable crystalline perchlorates. The mechanism of formation of the phosphorodichloridates is discussed. The phosphorodichloridates reacted with aromatic amines to give in high yield the corresponding 6-aryl-1-phenyl-taλ⁴-thia-1,2,6-triazapentalenes. With o-phenylenediamine reaction took place at one of the amino-groups to give the 6-o-aminophenyl-1-phenyl-6aλ⁴-thia-1,2,6-triazapentalenes or at both amino-groups to give 1,2-bis-(1-phenyl-6aλ⁴-thia-1,2,6-triazapentalen-6-yl)benzenes. The perchlorates reacted with 2-amino-4-methylpyridine to give in modest yield 6-(4-methyl-2-pyridyl)-1-phenyl-6aλ⁴-thia-1,2,6-triazapentalenes. The phosphorodichloridates also reacted with methylamine to give the previously reported 6-methyl-1-phenyl-6aλ⁴-thia-1,2,6-triazapentalenes. The phosphorodichloridates reacted with hydroxylamine and O-methylhydroxylamine to give, respectively, 6-hydroxy- and 6-methoxy-1-phenyl-6aλ⁴-thia-1,2,6-triazapentalenes. The results of spectral studies of these compounds are discussed in relation to structure. The phosphorodichloridates reacted with p-nitrophenylhydrazine and acetylhydrazine to give stable 6-p-nitrophenylamino- and 6-acetamido-1-phenyl-6aλ⁴-thia-1,2,6-triazapentalenes. 4-Methyl-5-(1-methyl-2-chlorovinyl)-2-phenyl-1,2,3-thiadiazolylium phosphorodichloridate reacted with sodium hydrogen sulphide to give 3,4-dimethyl-1-phenyl-6,6aλ⁴-dithia-1,2-diazapentalene, together with 3,5-dimethyl-1-phenylpyridazine-4-thione, but 7-chloromethylene-4,5,6,7-tetrahydro-2-phenylbenz-[d][1,2,3]thiadiazolylium phosphorodichloridate gave 6,7-dihydro-2-phenyl-5H-2aλ⁴,3-dithia-1,2-diazacyclopent[cd]indene quantitatively. The phosphorodichloridates reacted with potassium seleno-sulphate to give 6aλ⁴-thia-6-selena-1,2-diazapentalenes, a new class of four-electron three-centre bonded compound.