TiCl4−n-Bu4NX (X = I, Br, and Cl) Combination-Induced Coupling of α,β-Unsaturated Ketones with Aldehydes
journal contributionposted on 24.10.2001, 00:00 authored by Zhenfu Han, Shigeki Uehira, Hiroshi Shinokubo, Koichiro Oshima
A three-component coupling reaction between vinyl ketones, aldehydes, and halides has been developed with TiCl4−n-Bu4NX combined reagents. Treatment of vinyl ketones with a TiCl4−n-Bu4NI combination followed by an addition of a variety of aldehydes provides syn-α-iodomethyl-β-hydroxy ketones with high stereoselectivity. Methyltriphenylphosphonium iodide as well as n-Bu4NI acts efficiently as a halide source. The combination of TiCl4−n-Bu4NBr provides the corresponding bromo compounds in good yields. syn-α-Chloromethyl-β-hydroxy ketones are obtained with the TiCl4−n-Bu4NCl combination. A competitive experiment reveals that the order of relative reactivity of the combinations is TiCl4−n-Bu4NI > TiCl4−n-Bu4NBr > TiCl4−n-Bu4NCl.