Evidence for a nucleophilic anti-attack on the cleaved C(2)–oxygen bond in Cl2AlH-catalyzed ring-opening of 2-substituted 1,3-dioxolanes

The Cl2AlH-mediated ring-opening of 2-substituted cis-4-methyl-5-trifluoromethyl-1,3-dioxolanes was found to occur with regioselective cleavage of the O1–C2 bond by attack of the aluminum hydride from the direction anti to the departing oxygen. This stereochemical outcome, which appears to be unprecedented in the reductive cleavage of chiral acetals by aluminum reagents, is interpreted on the basis of theoretical calculations.