Synthesis of Heterocycles by HNTf2-Catalyzed C−H Functionalization of Vinyldiazo Compounds with 3-Hydroxyisoindolinone

A Brønsted acid catalyzed C−H functionalization of vinyldiazoacetates with 3-hydroxyisoindolinone has been developed. This methodology provides a general access to E-substituted isoindolinone vinyldiazo compounds in good yields and excellent diastereoseletivity with broad substrate generality under mild conditions, and with 4-substituted-2-diazo-3-butenoates produces fused bicyclic pyrrolidines. The reaction generally involves addition of the N-acyl ketiminium electrophile formed from the 3-hydroxyisoindolinone to the vinylogous position of vinyldiazo compounds that results in vinyldiazonium ion intermediates that undergo deprotonation to new vinyldiazo compounds or ring closure to fused bicyclic pyrrolidines.