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.
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