Regio- and diastereoselectivity in TiCl4-promoted reduction of 2-aryl-substituted cis-4-methyl-5-trifluoromethyl-1,3-dioxolanes

TiCl4-mediated reduction of both syn- and anti-(4S,5S)-2-aryl-4-methyl-5-trifluoromethyl-1,3-dioxolanes with Et3SiD furnished monodeuterated hydroxy ethers resulting from the same regio- and stereoselective C-O bond cleavage (yields >80%; 82-92% de). Deuteride addition to the benzylidene acetal and removal of the alkyl moiety from the reaction product gave (R)-(alpha-H-2)benzy] alcohol (90% ee), thus suggesting a new route to chiral 1-deuteriobenzyl alcohols. A mechanistic rationale is proposed and supported by theoretical calculations. (C) 2002 Elsevier Science Ltd. All rights reserved.