Reaction of Aromatic Aldehydes, Meldrum’s Acid, Monothiomalonamide, and Triethylamine: Synthesis, Structure, and Some Properties of New Stable Michael Adducts

Abstract

The reaction of monothiomalonamide with aromatic aldehydes and Meldrum’s acid in the presence of triethylamine yielded previously unknown stable Michael adducts – triethylammonium 5-[3-amino-1-(het)aryl-3-oxo-2-(thiocarbamoyl)propyl]-2,2-dimethyl-4-oxo-4H-1,3-dioxin-6-olates in 64–83% yields. The prepared adducts exist as a mixture of stereoisomers with a predominant trans-configuration of the hydrogen atoms at C1 and C2. The stereochemical and conformational features of the structure of the obtained compounds were also investigated using quantum chemical methods. Alkylation of the synthesized Michael adducts with N-aryl-2-chloroacetamides leads to 2,2′-thio-bis(N-arylacetamides). Among the new products, two samples were found that exhibit a pronounced antidote effect against the herbicide 2,4-D in laboratory and field experiments on sunflower seedlings.