Direct synthesis of indazole derivatives via Rh(iii)-catalyzed C-H activation of phthalazinones and allenes

A novel Rh(iii)-catalyzed annulation of phthalazinones or pyridazinones with various allenes was developed, leading to the formation of indazole derivatives bearing a quaternary carbon in moderate to good yields. The targeted products were synthesized via sequential C-H activation and olefin insertion, followed by beta-hydride elimination and intramolecular cyclization. The synthetic protocol proceeded efficiently with broad functional group tolerance, high atom efficiency and high Z-selectivity. The practicability of this method was proved by synthetic transformation.

Automated summary

A novel Rh(III)-catalyzed annulation method was developed for the synthesis of indazole derivatives with a quaternary carbon, through sequential C-H activation, olefin insertion, beta-hydride elimination, and intramolecular cyclization. The method showed good functional group tolerance, high atom efficiency, and high Z-selectivity, proving its practicality in synthetic transformations.