4-Methylpyrimidinium ylides II: Selective reactions of pyrimidinium ylideswith activated alkynes

The reaction of 4-methylpyrimidinium ylides (as 1,3-dipoles) with DMAD (dim ethyl acetylenedicarboxylate) and DFA (diphenylacetylene) as dipolarophiles is presented. 4-Methylpyrimidinium ylides did not react with DFA. A select ive route to obtain new azabicyclic structures derived from pyrimidine via the reaction of pyrimidinium ylides with DMAD is also presented. In additio n to the azabicyclic compounds, an unexpected betaine structure has been ob tained, and a possible mechanism for the reaction pathway is proposed. A se lective way to increase the proportion of azabicyclic compound or betaine w as determined.