Regiospecific Synthesis of Tetra-Substituted Furans
作者:Leiv K. Sydnes、Rustem Isanov、Myagmarsuren Sengee、Francesco Livi
DOI:10.1080/00397911.2012.748076
日期:2013.11.2
Abstract α,β-Unsaturated acetylenic γ-hydroxyketones have been shown to react with ethyl acetoacetate in a Michael-addition fashion and subsequently undergo cyclization followed by dehydration to give substituted furans with a predictable regiospecificity. The yields were good to excellent. A mechanism for the transformation is proposed, and this mechanism explains why furan formation does not take
Formation of N-Heterocycles from 1,1-Diethoxy-5-hydroxyalk-3-yn-2-ones
作者:Leiv Sydnes、Ingebjørg Nes
DOI:10.1055/s-0034-1378898
日期:——
When treated with hydrazine, guanidine, and hydroxylamine, 1,1-diethoxy-5-hydroxyalk-3-yn-2-ones undergo Michael addition and give the corresponding beta, beta-disubstituted alpha, beta-unsaturated olefinic ketones, which are unstable and undergo secondary reactions to form heterocyclic compounds. Hydrazine affords 3,5-disubstituted pyrazoles and hydroxylamine 5-hydroxy-4,5-dihydroisoxazoles in very good yields. Guanidine, however, furnishes complex reaction mixtures, which include the corresponding 2-aminopyrimidines. These results show that cyclization involves attack of the ketone moiety by the bisnucleophile reactive terminal group and not the hydroxyl group present in the starting material.