New electrophiles for asymmetric ring-opening reactions with (salen)M catalysts

The development of a catalytic method for the asymmetric opening of oxetanes is described. Intermolecular addition of TMSN3 to achiral, 3-substituted oxetanes provided 1,3-azidoalcohols in up to 40% ee. Substantially greater success was obtained in the intramolecular opening of achiral oxetanes with hydroxyl bearing 3-substituents. Either monomeric (salen)Co(III) or oligomeric (salen)Co(III) complexes were found to catalyze enantioselective formation of 3-substituted tetrahydrofurans and dihydrobenzofurans in high yield and enantioselectivity. The scope of the process is broad, producing a wide variety of substituted tetrahydrofurans and dihydrobenzofurans. The reactions can be conducted neat and with as low as 0.01 mol% catalyst loading.;Enantioselective iodoetherification of cis-alkenols catalyzed by (salen)M complexes was studied, and the key components necessary to achieve high enantioselectivity were identified. Using this knowledge, catalytic iodoetherifications and iodoaminations of terminal olefins were developed in up to 30% and 9% ee respectively, using (salen)Co(III) or (salen)Cr(III) catalysts. Also a racemic, catalytic intermolecular iodochlorination of cyclohexene is described.