ISSN:
0009-2940
Keywords:
Cuprates, organo-
;
1,6-Addition
;
Allenyl enolates
;
Nucleophiles, chiral, ambident
;
Electrophiles, regioselective reaction of
;
Electrophiles, stereoselective reaction of
;
Cieplak effect
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The regio- and stereoselectivity of the reaction of allenyl enolates obtained by 1,6-addition of lithium dimethylcuprate to acceptor-substituted enynes 1 with C and Si electrophiles is examined. It is found that allyl bromide reacts at C-4 to give 4-substituted 2,4-dienoates 2; in contrast, methyl triflate and carbonyl compounds react at C-2 to yield 2-substituted β-allenic esters 3-12. The hard electrophile chlorotrimethylsilane reacts at the enolate oxygen atom to provide allenyl enol ether 14. The regioselectivity of these trapping reactions depends only on the nature of the electrophile; the stereoselectivities, on the other hand, are a function of both the steric properties of the allenyl enolate and the type of electrophile. The regio-and stereoselectivities are rationalized in terms of charge control and frontier-orbital control, of kinetic and thermodynamic control, and of steric interactions in intermediates and transition states.
Additional Material:
1 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19931260134
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