The Alpha-Alkoxyallylation of Activated Carbonyl Compounds: A Novel Variant of the Michael Reaction
Hobbs, Steven John
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https://hdl.handle.net/2142/70220
Description
Title
The Alpha-Alkoxyallylation of Activated Carbonyl Compounds: A Novel Variant of the Michael Reaction
Author(s)
Hobbs, Steven John
Issue Date
1983
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Organic
Abstract
Five methods of alkoxyallylation at the alpha carbon of activated carbonyl compounds are proposed and explored. The product of alkoxyallylation, which are enol ethers, are protected equivalents of the adducts obtained from the Michael reaction of (alpha),(beta)-enals with activated carbonyl compounds.
Enolic or readily enolizable carbonyl compounds undergo alkoxyallylation upon reaction with ethoxyallene or acetals of (alpha),(beta)-enals at temperatures between 25(DEGREES)C to 200(DEGREES)C. Less acidic activated carbonyl compounds were best alkoxyallylated with the acetals above with nickel(II) acetylacetonate catalyst. The alkoxyallylation of activated carbonyl compounds using (gamma)-alkoxyallyl alcohols and (alpha)- or (gamma)-alkoxy allylic chlorides as electrophiles were briefly explored.
The mechanism of the methods of alkoxyallylation probably involves direct C-allylation of the carbonyl compound on the (alpha)-position of an alkoxyallyl cation or equivalent electrophilic species, or an indirect pathway via O-allylation at the (alpha)-position of the cation, followed by Claisen rearrangement of the resulting (alpha)-alkoxyallyl enol ether. Attempts to prepare these enol ethers by selenoxide elimination at 25(DEGREES)C provided instead the corresponding Claisen rearrangement products. The relationship between these methods of alkoxyallylation, the Michael reaction and appropriated cases of the Claisen rearrangement are also discussed.
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