IMDAV reaction between phenylmaleic anhydride and thienyl(furyl)allylamines: Synthesis and molecular structure of (3a SR,4 RS,4a RS,7a SR)-5-oxothieno- and (3a SR,4 SR,4a RS,7a SR)-5-oxofuro[2,3- f ]isoindole-4-carboxylic acids

The title compounds C 24 H 21 NO 3 S, I, and C 24 H 21 NO 4, II, are the products of the IMDAV reaction between phenylmaleic anhydride and thienyl(furyl)allylamines. Their molecular structures comprise fused tricyclic systems containing thiophene, cyclohexene and pyrrolidine rings (I) or furan, cyclohexene and pyrrolidine rings (II). The central cyclohexene and pyrrolidine rings in both compounds adopt slightly twisted boat and envelope conformations, respectively. The dihedral angles between the basal plane of the pyrrolidine ring and the thiophene (in I) or furan (in II) ring plane are 22.74 (16) and 26.29 (5)°, respectively. The nitrogen atom both in I and II has practically planar environment [the sums of the bond angles are 359.8 and 358.9°, respectively]. In the crystal of I, the molecules form hydrogen-bonded zigzag chains along [010] through strong intermolecular O - H⋯O hydrogen bonds involving carboxylic and keto groups, whereas in the crystal of II, the molecules are joined into centrosymmetric dimers by strong O - H⋯O hydrogen bonds between the carboxylic groups. In II, the atoms involved into these hydrogen bonds (and hence the whole carboxylic group) are disordered over two sets of sites with an occupancy ratio of 0.6:0.4. Compounds I and II crystallize as racemates consisting of enantiomeric pairs of the 3aSR,4RS,4aRS,7aSR and 3aSR,4SR,4aRS,7aSR diastereomers, respectively. © © Toze et al. 2018.