NEIGHBORING GROUP PARTICIPATION IN LEWIS ACID-PROMOTED [3- THE STEREOCONTROLLED SYNTHESIS OF TRICYCLIC ETHERS(4] AND [3+5] ANNULATIONS )

Citation
Ga. Molander et Ko. Cameron, NEIGHBORING GROUP PARTICIPATION IN LEWIS ACID-PROMOTED [3- THE STEREOCONTROLLED SYNTHESIS OF TRICYCLIC ETHERS(4] AND [3+5] ANNULATIONS ), Journal of organic chemistry, 58(22), 1993, pp. 5931-5943
Citations number
90
Categorie Soggetti
Chemistry Inorganic & Nuclear
ISSN journal
00223263
Volume
58
Issue
22
Year of publication
1993
Pages
5931 - 5943
Database
ISI
SICI code
0022-3263(1993)58:22<5931:NGPILA>2.0.ZU;2-7
Abstract
A variety of 1,4- and 1,5-keto aldehydes derived from cycloalkanes are coupled with the bis(trimethylsilyl) enol ether of methyl acetoacetat e in the presence of either TMSOTf or TrSbCl6 to generate tricyclic et hers. The reactions proceed with excellent regiochemical control by a mechanism involving neighboring group participation. This mechanism in volves initial formation of a bicyclic oxocarbenium ion intermediate f rom the keto aldehyde substrates. The geometries of selected bicyclic intermediates have been optimized using the AM1 method allowing succes sful prediction of the stereochemical outcomes in the cyclization in m ost cases. Epimerization of alpha-chiral keto aldehyde substrates does not appear to occur in these Lewis acid-promoted annulation reactions .