Abstract
Stable 3-methyl-1-phenacylbenzotriazolium ylide (2) adds acetylene-carboxylic esters to form tricycles (3). Araldehydes react with two moles of 2 give poly-substituted 4,5-dihydrofurans (5). The pyrazoloquinoxaline structure of 3 was confirmed by X-ray analysis.