Substrate-Dependent Selective Synthesis of Diversely Functionalized Indazole Derivatives Based on CHA-Initiated Cascade Reactions.

Presented herein is a substrate-dependent selective synthesis of diversely functionalized indazole derivatives based on the cascade reaction of N-nitrosoanilines with diazo compounds. To be specific, indazole attached with a benzoyl carbamate moiety is obtained from the reaction of N-nitrosoaniline with diazo homophthalimide containing a N-alkyl unit. The product is formed through nitroso-directed C-H alkylation, followed by intramolecular C-nucleophilic addition, intermolecular O-nucleophilic addition, C-C bond cleavage, and dehydrogenation. When diazo homophthalimide bearing a N-phenyl unit is used, the in situ formed benzoyl carbamate-decorated indazole undergoes the second O-nucleophilic addition, followed by C-N bond cleavage and phenyl carbamate elimination to afford indazole attached with a benzoate moiety. In general, this novel synthetic protocol features readily available substrates, valuable products, excellent chemo-selectivity, intriguing reaction pathways, high efficiency, and ready scalability.