Michael reaction of enyne derivatives of Meldrum's acid in water: Synthetic approach for creating a C–N/C–S bonds inwith low reactive nucleophiles

Abstract

The mild addition at the triple bond of low reactive amines and thiols to 5-(Prop-2-yn-1-yliden)-2,2-dimethyl-1,3-dioxane-4,6-diones (such as 4-nitroaniline, diphenylamine, 2-mercaptobenzothiazole, and others) in aqueous medium results easily in corresponding Michael adducts in up to 99 % yields. Reactivity estimation results for Meldrum's acid enyne derivatives allow to place them among the most powerful acetylenic Michael acceptors (like DMAD). The authors have also shown regioselectivity for the addition of several bifunctional derivatives of imidazole and benzimidazole to enynes with the C–S bond formation. Polycentric nature of substrates and amine products, together with the fact of the 1,3-dioxane-4,6-dione fragment presence, provide extended options for chemical transformations of Meldrum's acid enyne derivatives to apply widely in the direct synthesis.