Experimental and theoretical investigation of the reaction of a 3-amidothiophene derivative with various carbonyl compounds

The reactions of a 3-amidothiophene derivative, which is a partial structure of penthiopyrad, with various carbonyl compounds were investigated. Depending on the carbonyl compound that was used as a reactant, different products (alkenes and bis-products) were obtained from the attack of the carbon at the 2-position of the 3-amidothiophene on the carbonyl compounds. Density functional theory (DFT) calculations revealed that dehydration conditions were important for the first carbonyl addition to shift the reaction toward the product, as the products are more unstable than reactants other than aldehyde. The DFT calculations also suggested that the relative stability of the alkenyl state determined whether the second bis-product formation would proceed; i.e., the relatively unstable disubstituted alkene led to bis-products, and the stable trisubstituted or conjugated alkene yielded alkenyl products.