ORGN 20 |
| K.A. Woerpel and Stephen Chamberland. Department of Chemistry, University of California, 516 Rowland Hall, Irvine, CA 92697-2025 |
| A remote (C-4) benzyloxy substituent strongly stabilizes one particular conformer of eight-membered-ring oxocarbenium ion intermediate 2a by a through-space electrostatic effect. Kinetically controlled nucleophilic attack on this intermediate by trimethylsilyl cyanide favors the 1,4-trans product (3a) with high diastereoselectivity. X-ray crystallographic analysis of an amide derivative of 3a confirms the 1,4-trans relationship in the major diastereomer. Nucleophilic addition of trimethylsilyl cyanide to the corresponding C-4-methyl-substituted oxocarbenium ion (2b), however, is nonselective. A computational model has been developed and experimentally validated that predicts the low energy conformers of eight-membered ring oxocarbenium ions containing a benzyloxy or methyl substituent at C-3, C-4, or C-5. |
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New Reactions and Methodology
8:00 AM-12:00 PM, Sunday, March 28, 2004 Anaheim Convention Center -- 303A, Oral
Division of Organic Chemistry |
