Chiral Benzazaborole-Catalyzed Regioselective Sulfonylation of Unprotected Carbohydrate Derivatives.

Chiral benzazaborole-catalyzed regioselective sulfonylations of unprotected carbohydrate derivatives have been developed. This methodology enables direct regioselective functionalization of the secondary OH group in carbohydrate in the presence of the primary OH group. By using the chiral organoboron catalysis, kinetic resolution of the carbohydrate derivatives was also achieved.

Chiral benzazaboroles as catalysts for enantioselective sulfonylation of cis-1,2-diols.

A newly developed benzazaborole smoothly catalyzed the enantioselective sulfonylation of cis-1,2-diols. Using a chiral benzazaborole/NMI co-catalyst system, various sulfonate esters were prepared in high yields with good enantioselectivities.

A chiral organic base catalyst with halogen-bonding-donor functionality: asymmetric Mannich reactions of malononitrile with N-Boc aldimines and ketimines.

A chiral organic base catalyst with halogen-bonding-donor functionality has been developed. This quinidine-derived acid/base catalyst smoothly promoted the asymmetric Mannich reaction of malononitrile and various N-Boc imines with up to 98% ee. The cooperative interaction with both substrates was responsible for the high activity that allowed a reduction of the catalyst amount to 0.