Catalytic, Enantioselective Cycloaddition of Pyrrole-2methides with Aldehydes toward a Synthesis of 2,3-Dihydro-1-pyrrolizin-3-ols.

An organocatalytic, highly enantioselective [6 + 2]-cycloaddition of 2-methide-2-pyrroles with aryl acetaldehydes represents a novel and straightforward route toward densely substituted 2,3-dihydro-1-pyrrolizin-3-ols, which were generated with good yields and high enantio- and diastereoselectivity. This one-step process involves a BINOL-phosphoric acid catalyzed reaction of 1-pyrrole-2-carbinols with aryl acetaldehydes via the corresponding hydrogen-bonded, chiral 2-methide-2-pyrroles.