Abstract 5-Arylmethylene-2, 2-dimethyl-1, 3-dioxane-4, 6-diones reacted with 5-isopropenyl- 2, 3-dihydrothio-phene 1, 1-dioxide to give the corresponding ortho-addition products, 5-aryl- 2', 2', 7-trimethyl-3, 3a, 5, 6-tetra-hydro-2 H-spiro [1-benzothiophene-4, 5'-[1, 3] dioxane]-4', 6'-dione 1, 1-dioxides. Their aminolysis resulted in opening of the 1, 3-dioxane ring and formation of 4-carbamoyl-7-methyl-2, 3, 3a, 4, 5, 6-hexahydro-1-benzo-thiophene-4- ...