Enantioselective dearomative [3 + 2] cycloadditions of indoles with azomethine ylides derived from alanine imino esters
Catalytic, enantioselective [3 + 2] cycloadditions of azomethine ylides derived from alanine imino esters with 3-nitroindoles are reported. The dearomative cycloaddition reactions occur in the presence of a catalyst generated in situfrom Cu(OTf)2 and (R)-Difluorphos to form exo′-pyrroloindoline cycloadducts and establish four contiguous stereogenic centers, two of which are fully substituted. The exo′-pyrroloindoline products are formed in moderate-to-good yields (39–85%) with high diastereoselectivities (up to 98:1:1 dr) and enantioselectivities (up to 96% ee).
This article is published as Gerten, Anthony L., and Levi M. Stanley. "Enantioselective dearomative [3+ 2] cycloadditions of indoles with azomethine ylides derived from alanine imino esters." Organic Chemistry Frontiers 3, no. 3 (2016): 339-343. doi: 10.1039/C5QO00346F. Posted with permission.