Junjappa-ila annulation: α-oxoketene dithioacetal mediated synthesis of substituted benzotriazoles

(Chemical Equation Presented) 2-(1-Benzyl-1H-1,2,3-triazole-4-yl)-3- methylsulfanyl-5-oxo-5-substituted-pent-2-enenitrile 3a-e were obtained in good yields by condensation of (1-benzyl-1H-1,2,3-triazole-4-yl)acetonitrile (1) with various α-oxoketene dithioacetals 2a-e in the presence of sodium hydride. The intermediates 3a-e underwent facile acid-induced cyclization in the presence of PTSA to afford the corresponding benzotriazoles 4a-e in moderate yields.