Enantioselective dearomative [3+2] cycloaddition of 2-nitrobenzofurans with aldehyde-derived Morita-Baylis-Hillman carbonates.

The phosphine-catalyzed asymmetric dearomative [3+2] cycloaddition of 2-nitrobenzofurans with aldehyde-derived Morita-Baylis-Hillman (MBH) carbonates or allenoate was developed. The reaction with MBH carbonates resulted in a series of cyclopentabenzofurans containing three contiguous stereocenters with good to high yields, diastereoselectivities and enantioselectivities. The use of allenoate also gave the target product with moderate enantioselectivity.