Cycloaddition reactions of cycloimmonium ylides with triphenylcyclopropene

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Abstract
Cycloaddition reactions of 1,2,3-triphenylcyclopropene (TPP) with a variety of substituted pyridinium dicyanomethylides (1) give the corresponding 1,2,3-triphenylindolizines (3)[and (4)], 6-cyano-7,8,9-triphenyl-4H-quinolizines (5), 4-cyano-1,2,3-triphenyl-4H-quinolizines (6), and/or 1 : 1 adducts (7)[and (8)], depending on the substituents and their positions. The effect of substituents on the course of the reaction is discussed qualitatively. The pyrazinium dicyanomethylide (16) with TPP produces the 7-azaindolizine (19), whereas pyridazinium (17) and phthalazinium (18) dicyanomethylides give the primary adducts (20) and (21), respectively. Reaction of pyridinium bis(alkoxycarbonyl)methylides (22) with TPP gives, however, generally poor or no yield of the indolizines.

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