α-( N -Alkyl-N-heteroarenium)-α-diazoacetates: synthesis and reactivity of a novel class of 'onium' diazo compounds.

Treatment of alkyl α-( N -heteroaryl)-α-diazoacetates with alkylating reagents affords diazoacetate N-heteroarenium salts. These novel 'onium' diazo compounds are mostly yellow solids, displaying increased thermal and acid stability. Their tetrafluoroborates undergo rhodium catalyzed [2 + 1] and Doyle-Kirmse reactions under mild conditions, suggesting the N -quaternization an effective means of elimination of N -coordination caused catalyst toxicity.