Epoxide Enantioselective, from halo ketone

Enantioselective reductions. The neat reagent (1), prepared from ( + )-< -pinene, reduces aryl a-halomethyl ketones slowly but in high chemical yield to (R)-halohydrins in 90-96% ee, but optical induction is mediocre in the case of aliphatic a-halo ketones (35-66% ee). The chiral halohydrins are useful precursors to chiral epoxides. 

Asymmetric synthesis of 8-functionalized optically active secondary alcohols was realized hy TarB-N02-catalyzed enantios-elective reduction of a-halo ketones to an intermediate terminal epoxide and sequential ring opening with various nucleophiles. Optically active st)Tene oxide was prepared from a-bromoacetophenone with NaBH4 and TarB-N02 in high yield and with high enantioselectivity (98% 3ueld and 94% ee). fi-Functionalized secondary alcohols could be obtained from the epoxides by nucleophilic attack under appropriate conditions (eq41). 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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