Reaction of 3-Ethoxycarbonyl-2-methylthiothiazolo [2, 3-α] isoquinolinium Sulfate with Active Methyl and Methylene Compounds

Abstract

The reaction of 3-ethoxycarbonyl-2-methylthiothiazolo [2, 3-a] isoquinolinium sulfate (II) with various active methyl and methylene compounds in the presence of a base afforded mesoionic compound (V, VI) substituted by methylthio group with active methylene and pyrrolo [2, 1-a] isoquinoline (=benzoindolizine) derivatives (III, IV, VII, VIII, IX, Xa, b, XI) with opening of the thiazole ring and formation of a pyrrole ring. 1, 3-Diethoxycarbonyl-2-methylthiopyrrolo [2, 1-a] isoquinoline (Xb) was converted to 1-ethoxycarbonyl-2-methylthiopyrrolo [2, 1-a] isoquinoline (XII) by the treatment with polyphosphoric acid (PPA).