Dual Photoredox/CpTi(IV)-Catalyzed Reductive Cyclization of Tertiary Bromide with Nitrile for Constructing 4a,9a-Heterocycle-Fused Tetrahydrocarbazole

In this study, dual photoredox/CpTi(IV) catalysis has been developed for the reductive cyclization of 3a-bromo-hexahydropyrroloindoline or 3-bromo-tetrahydrofuroindole with the appendage nitrile, providing rapid access to a series of 4a,9a-heterocycle-fused tetrahydrocarbazoles in satisfactory yields. Utilizing this methodology, formal synthesis of minfiensine, strictamine, and aspidophylline A was achieved based on a sequential catalytic asymmetric bromocyclization/reductive cyclization with improved synthetic efficiency for demonstrating its broad synthetic potential.