ISSN:
0570-0833
Keywords:
Cycloaddition
;
Allyl cations
;
Cations
;
Synthetic methods
;
Cycloheptanes
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The reaction of allyl cations and 1,3-dienes affords seven-, five-, and six -membered rings as well as products of electrophilic substitution and linear 1:1-adducts. In this review article, preparative and mechanistic advances are summarized with special emphasis on the synthesis of seven-membered carbocycles. For the first time, a comprehensive mechanistic description is presented: Three classes A, B, and C correlate product type and stereochemistry with the nucleophilicity of the diene, the electrophilicity of the allyl cation intermediate, and the donor capacity of the group Y attached to the central carbon of the allylic moiety. The problem “allylic resonance versus nucleophilic participation of Y” is discussed and experimental evidence is adduced for some participation of Y as a function of its nucleophilicity. For cyclopentenyl cations, enhanced charge separation and electrophilicity are postulated, even when Y is a good donor, due to the structurally enforced polarity of the π-allyl system.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/anie.198400013
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