Development of Synthetic Tools Using Ynol Ether Ionic Chemistry

1. Development of Synthetic Tools Using Ynol Ether Ionic Chemistry Benoit Daoust, Département de Chimie-Biologie, Université du Québec à Trois-Rivières, Trois-Rivières, Québec G9A 5H7 Olefin attack on cationic ketene ; formation of ,β-unsaturated ketone and unsaturated hemiketals: We investigate the possibility of producing hemiketals 5 from homoallylic ynol ethers 2. Ynol ethers 2 were prepared from alcohol 1. Ynol ethers 2 were then reacted with a source of non-nucleophilic H+ (“solid acid” resin ) in the hope of producing a hemiketal (such as 5). Only the ynol ether hydrolysis product 6 was isolated, no cyclization product could be observed. Using HgO, Hg(OAc)2 or Ru(p-cymene)Cl2 as catalysts lead to the same undesired product 6. We then try to activate ynol ethers 1 by transforming them to vinyl esters. Reacting 2 with benzoic acid, trifluorobenzoic acid and ammonium salts only lead to the same undesired acetate 6. Reaction with TsOH recently lead to a surprisingly stable hemi ortho ester 7 (> 50% yield). We then treated the latter with HgO, Hg(OAc)2 or Ru(p-cymene)Cl2. To our surprise, it reacted very slowly and only lead the same undesired acetate 6. We will next investigate the very intriguing formation of “stable” hemi ortho ester 7. October 2009 ACS PRF# 46293-B1