Reactions of 2-benzylidene-3-methyl-4-nitro-2,5-dihydrothiophene 1,1-dioxide with CH acids

2-Benzylidene-3-methyl-4-nitro-2,5-dihydrothiophene 1,1-dioxide reacted with acyclic CH acids (acetylacetone, diethyl malonate, and its derivatives) according to the 1,4-addition pattern, whereas reactions of the title compound with cyclohexane-1,3-dione and 5,5-dimethylcyclohexane-1,3-dione (dimedone) were complicated by subsequent intramolecular heterocyclization leading to thieno[3,2-b]chromene derivatives.