Studies on the Reactions of Heterocyclic Compounds. VI. 1, 3-Dipolar Cycloaddition Reaction of Disubstituted Methylides of Isoquinoline and Pyridine with Acetylenic Compounds

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Tetramethyl 3, 10b-dihydropyrrolo [2, 1-α] isoquinoline-1, 2, 3, 3-tetracarboxylate (VI) was isolated for the first time as the primary addition product of a reaction between isoquinolinlium bis (methoxycarbonyl) methylide (V) and dimethyl acetylenedicarboxylate (IV). Treatment of VI with hydrogen chloride and then with potassium carbonate resulted in its isomerization into 2, 3-dihydropyrrolo [2, 1-α] isoquinoline derivative (VII). In the reaction of isoquinolinium dicyanomethylide (XI) with IV, the isomerized 2, 3-dihydro compound (XIII) and the eliminated product (XIV) were produced, instead of their primary adduct (XII). The relation between a substituent group in the 2, 3-dihydrotype compounds and their reactivity was examined. On the other hand, in the reaction of disubstituted pyridinium methylides with acetylenic compounds, only aromatized products were obtained.