(+/-)-trans-6,7-Dimethoxy-1-Oxo-3-(2-Thienyl)isochroman-4-Carboxylic Acid

Abstract

The title compound, C<inf>16</inf>H<inf>14</inf>O<inf>6</inf>S, was synthesized by the reaction of 6,7-dimethoxy-homophthalic anhydride with thio-phene-2-carbaldehyde in the presence of 4-(dimethyl-amino)pyridine (DMAP) as a basic catalyst. The thio-phene ring of the title mol-ecule is disordered over two sites with occupancies of 0.877 (3) and 0.123 (3). The disorder corresponds to an approximate 180° rotation of the thio-phene ring with respect to the C - C bond linking it to the rest of the mol-ecule. The six-membered ring of the 3,4-dihydro-isochromanone ring system is not planar [puckering parameters Q T = 0.571 (2) Å, = 115.2 (2)° and = 99.1 (2)°]. The benzene ring of the 3,4-dihydro-isochromanone ring system makes dihedral angles of 75.0 (2) and 77.2 (5)° with the disordered thio-phene rings. Inter-molecular O - H⋯O and C - H⋯O hydrogen bonds, as well as C - H⋯π inter-actions, lead to the observed supra-molecular structure.