Kangying Li

Asymmetric carbonyl reduction with borane catalyzed by chiral phosphinamides derived from l-amino acid

Abstract Two types of chiral phosphinamide catalysts 3a–d and 4a–c were prepared from l -phenylalanine and l -proline, respectively. Their applications in the asymmetric borane reduction of prochiral ketones were investigated. The chiral secondary alcohols were obtained with excellent chemical yields and moderate to high enantiomeric excesses.

Regio- and stereoselective ring-opening of epoxides using organic dithiophosphorus acids as nucleophiles

Abstract A practical method for the synthesis of β-hydroxymercaptans has been successfully developed through the ring-opening of epoxides with organic dithiophosphorus acids 1 . Highly regio- and stereoselective products, β-hydroxyalkyl dithiophosphates, which were transformed to the corresponding synthetically valuable β-hydroxymercaptans by further reduction, were obtained under mild reaction conditions without any catalyst or promoter. Highly enantioselective ring-opening reaction of cyclohexene epoxide with 1 was realized in the presence of a chiral (salen)Ti(IV) complex.

SYNTHESIS OF A NEW CHIRAL o-HYDROXYARYLDIAZAPHOSPHONO- DIAMIDE AS LIGAND CATALYSTS FOR ASYMMETRIC SILYLCYANATION OF AROMATIC ALDEHYDES

ABSTRACT A new chiral o-hydroxyaryldiazaphosphonodiamide 1 was synthesized from (−)-α-methylbenzylamine, it was found to be efficient ligand for the Ti(O-iPr)4 catalyzed asymmetric trimethylsilylcyanation of aldehydes. Corresponding aromatic cyanohydrins were obtained in good chemical yield and enantiomeric excesses (e.e.s) up to 90%.

NEW CHIRAL PHOSPHORUS CATALYSTS DERIVED FROM (S)-BINAPHTHOL FOR HIGHLY ENANTIOSELECTIVE REDUCTION OF ACETOPHENONE BY BORANE

Abstract New chiral (+)-2,2′-O,O-(1,1′-binaphthyl)-dioxo-N,N-diethylphospholidine 1 and its borane complex 3 were prepared from (S)-binaphthol and their use as catalysts in enantioselective borane reductions of prochiral acetophenone were investigated. Enantiomeric excesses of up to 98.5% have been obtained using 6 mol% of 1 at room temperature and using 6 mol% of 3 at 100°C.