Diastereoselective construction of carbo-bridged polyheterocycles by a three-component tandem annulation reaction.

By a hydroamination-induced tandem annulation process, we herein report a new three-component reaction for room temperature construction of carbo-bridged polyheterocycles with exclusive diastereoselectivity, which features readily available feedstocks, catalyst-free conditions, good substrate and functionality compatibility, no need for transition metal catalysts, and high step and atom efficiency. The products are formed via initial formation of 1,2-dihydro-3 H -pyrazol-3-one nucleophiles from but-2-ynedioates and hydrazine followed by 2,4-difunctionalization of N -heteroarenium salts. Given that the obtained products possess structurally important tetrahydroquinoline and pyranopyrazole motifs, the developed chemistry is anticipated to be further applied to the discovery of functional molecules including biomedical ones.