A Direct and Selective Syntheses of α,α-Dichloro- and α-Chloro-ethyl Ketones by the Reaction of Alkyl Carboxylates with 1,1-Dichloroethyllithium

1,1-Dichloroethyllithium (5), generated by treating 1,1-dichloroethane (4) with lithium diisopropylamide (LDA) or n-butyllithium, reacted with alkyl carboxylates to afford the corresponding α,α-dichloro- or α-monochloro-ethyl ketones selectively in good to high yields. According to the above alkylation method, synthetic intermediates of Taxol, optically active α,α-dichloroethyl polyoxyketone 2 and α-chloroethyl polyoxyketone 3, were respectively synthesized from optically active methyl polyoxycarboxylate 1 in good yields.