A new method for the synthesis of azaheterocycles based on cascade reactions of nitrogen- and phosphorus-containing ylides with methyl diazoacetate

A new approach to functionally substituted pyrazoles and pyridazines based on the interaction of diazoesters with triphenylphosphonium or pyridinium carbonyl ylides and subsequent reactions of the so formed reactive azines with a further equivalent(s) of the initial ylides followed by a cyclocondensation into the corresponding five- or six-membered heterocycles is described.