Enantioselective reduction of benzofuryl halomethyl ketones:: asymmetric synthesis of (R)-bufuralol

Enantioselective reduction of representative 2-(bromoacetyl)- and 2-(chloroacetyl)benzofurans with (-)-B-chloro-diisopinocampheylborane and by transfer hydrogenation with formic acid/triethylamine in the presence of RhCl[R,R-TsD-PEN](C5Me5) is described. Transfer hydrogenation of the chloro ketones produced the corresponding chlorohydrins of >= 95% ee. (R)-Bufuralol of 96% ce was prepared from the corresponding chloro ketone by transfer hydrogenation-substitution. (c) 2005 Elsevier Ltd. All rights reserved.