C2-SYMMETRICAL 4,4',5,5'-TETRAHYDROBI(OXAZOLES) AND 4,4',5,5'-TETRAHYDRO-2,2'-METHYLENEBIS[OXAZOLES] AS CHIRAL LIGANDS FOR ENANTIOSELECTIVE CATALYSIS

The synthesis of a series of enantiomerically pure, C2-symmetric 4,4',5,5'-tetrahydro-2,2'-methylenebis[oxazoles] and 4,4',5,5'-tetrahydro-2,2'-bi(oxazoles) is reported. Copper complexes with anionic tetrahydromethylenebis[oxazole] ligands are efficient catalysts for the enantioselective cyclopropane formation from olefins and diazo compounds (up to 96% ee in the reaction of styrene with menthyl diazoacetate). Tetrahydrobi(oxazole)iridium(I) complexes were found to catalyze transfer hydrogenations of aryl alkyl ketones with i-PrOH (up to 91% ee). Tetrahydrobi(oxazole)palladium complexes can be used as enantioselective catalysts for allylic nucleophilic substitution (up to 77% ee in the reaction of PhCH = CHCH(OAc)Ph with NaHC(COOMe)2).