Use of conformational constraint to promote 8-endo phenol epoxide cyclizations

ORGN 354

James R. Vyvyan, vyvyan@chem.wwu.edu, Kyle S. Breakey, breakek@cc.wwu.edu, Travis C. McMahon, mcmahot@cc.wwu.edu, and Erik W. Werner, wernererik@hotmail.com. Department of Chemistry, Western Washington University, 516 High Street, Bellingham, WA 98225-9150
Inclusion of a Z-olefin in the tether between an epoxide and a phenolic nucleophile reduces conformational degrees of freedom and makes an 8-endo cyclization competitive with epoxide rearrangement and 7-exo cyclization under acidic conditions. This strategy represents a biomimetic approach to members of the heliannuols, a family of allelopathic compounds isolated in small quantities from the common sunflower, Helianthus annuus. Preparation of cyclization substrates and cyclization studies using Lewis acids, most notably triphenylphosphinegold(I) triflamide, will be presented. Sonogashira-type coupling of 1-trimethylsilyl-6-methyl-5-hepten-1-yne and an aryl iodide, followed by stereoselective semi-hydrogenation of the alkyne, deprotection of a phenol, and selective epoxidation of the trisubstituted olefin provides the cyclization substrates.

 

Heterocycles and Aromatics, Molecular Recognition and Self Assembly
8:00 PM-10:00 PM, Tuesday, April 8, 2008 Morial Convention Center -- Hall A, Poster

Division of Organic Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008