Regio- and Diastereocontrol in Carbonyl Allylation by 1-Halobut-2-enes with Tin(II) Halides

Regio- and diastereoselective carbonyl allylations of 1-halobut-2-enes with tin(II) halides are described. Tin(II) bromide in a dichloromethane−water biphasic system is an effective reagent for unusual α-regioselective carbonyl allylation of 1-bromobut-2-ene to produce 1-substituted pent-3-en-1-ols....

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Published inJournal of organic chemistry Vol. 65; no. 2; pp. 494 - 498
Main Authors Ito, Akihiro, Kishida, Masayuki, Kurusu, Yasuhiko, Masuyama, Yoshiro
Format Journal Article
LanguageEnglish
Published WASHINGTON American Chemical Society 28.01.2000
Amer Chemical Soc
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Summary:Regio- and diastereoselective carbonyl allylations of 1-halobut-2-enes with tin(II) halides are described. Tin(II) bromide in a dichloromethane−water biphasic system is an effective reagent for unusual α-regioselective carbonyl allylation of 1-bromobut-2-ene to produce 1-substituted pent-3-en-1-ols. The addition of tetrabutylammonium bromide (TBABr) to the biphasic system produces 1-substituted 2-methylbut-3-en-1-ols via usual γ-addition which is opposite to the α-addition without TBABr. The γ-addition to aromatic aldehydes exhibits anti-diastereoselectivity, while that to aliphatic aldehydes is not diastereoselective. The allylation of benzaldehyde by 1-chlorobut-2-ene in 1,3-dimethylimidazolidin-2-one (DMI) does not occur with tin(II) chloride or bromide but does proceed with tin(II) iodide and exhibits γ-syn selectivity which is unusual for a Barbier-type carbonyl allylation. In the carbonyl allylation by 1-chlorobut-2-ene with any tin(II) halide, the addition of tetrabutylammonium iodide (TBAI) accelerates the reaction and enhances γ-syn selectivity. The use of tin(II) iodide and TBAI produces 2-methyl-1-phenylbut-3-en-1-ol with high yield and high syn-diastereoselectivity. The syn-diastereoselective carbonyl allylation of 1-chlorobut-2-ene using tin(II) iodide, a catalytic amount of TBAI, and NaI in DMI−H2O is applied to various aldehydes.
Bibliography:ark:/67375/TPS-MFZSDC9X-2
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ISSN:0022-3263
1520-6904
DOI:10.1021/jo991403o