Formation of N-Heterocycles from 1,1-Diethoxy-5-hydroxyalk-3-yn-2-ones
摘要:
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.
Toward the Synthesis of Modified Carbohydrates by Conjugate Addition of Propane-1,3-dithiol to<i>α</i>,<i>β</i>-Unsaturated Ketones
作者:Stig Valdersnes、Ingrid Apeland、Guri Flemmen、Leiv K. Sydnes
DOI:10.1002/hlca.201200423
日期:2012.11
various conditions. The unprotected hydroxy ketones underwent cyclization during the dithiol addition and gave the corresponding 3‐(diethoxymethyl)‐2‐oxa‐6,10‐dithiaspiro[4.5]decan‐3‐ols 5 in 80–90% yield as the only products (Scheme 3 and Table 1). These products can be regarded as partly modified carbohydrates in the furanose form. When the benzyl‐protected analogues 10‐Bn of the 1,1‐diethoxy‐5‐hydroxypent‐3‐yn‐2‐one
Synthesis and Reactivity of 4-Amino-Substituted Furfurals
作者:Uranbaatar Erdenebileg、Inger Høstmark、Karina Polden、Leiv K. Sydnes
DOI:10.1021/jo4026308
日期:2014.2.7
reaction with secondaryamines followed by treatment with acid in a mixture of THF and water. The stability of the furfurals depends to some extent on the nature of the amino group, whereas the reactivity has been shown to be reagent-dependent. When treated with phosphorus ylids, the expected alkenes are formed with E configuration in high yields, but when exposed to nitroalkanes under basic conditions
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.