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 in | Journal of organic chemistry Vol. 65; no. 2; pp. 494 - 498 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
WASHINGTON
American Chemical Society
28.01.2000
Amer Chemical Soc |
Subjects | |
Online Access | Get full text |
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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. |
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Bibliography: | ark:/67375/TPS-MFZSDC9X-2 istex:503B7CF35185C7D16724979AB720A761DF32FB5E ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0022-3263 1520-6904 |
DOI: | 10.1021/jo991403o |