ISSN:
1434-193X
Keywords:
[2,3]-Wittig rearrangement
;
Dienolates
;
Alcohols
;
Aldol addition
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The [2,3]-Wittig rearrangement of dienolates generated from α-allyloxy-substituted α,β- and/or β,γ-unsaturated esters 4/5a-g has been investigated. The rearrangement proceeds with high yield and diastereoselectivity to afford 3-hydroxy-3-alkyloxycarbonyl-substituted 1,5-hexadienes 6a-e. The influence of the reaction conditions and of various substituents on the rearrangement has been studied. A transition state structure is suggested in order to explain the simple diastereoselectivity observed. The starting material for the rearrangement was prepared utilizing an aldol condensation strategy. The α-allyloxy-substituted esters 2a-c were deprotonated and treated with various ketones to chemoselectively afford the alcohols 3a-g. Thionyl chloride mediated elimination provided the desired unsaturated esters 4/5a-g as starting materials for the rearrangement. The difference in reactivity between an enolate and a dienolate is explained on the basis of a DFT quantum chemical calculation of the HOMO/LUMO energy gap.
Additional Material:
7 Tab.
Type of Medium:
Electronic Resource
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