IMDAV reaction between phenyl-maleic anhydride and thien-yl(fur-yl)allyl-amines: synthesis and mol-ecular structure of (3aSR,4RS,4aRS,7aSR)-5-oxothieno- and (3aSR,4SR,4aRS,7aSR)-5-oxofuro[2,3-f]iso-indole-4-carb-oxy-lic acids.

The title compounds C24H21NO3S, I, and C24H21NO4, II, are the products of the IMDAV reaction between phenyl-maleic anhydride and thien-yl(fur-yl)allyl-amines. Their mol-ecular structures comprise fused tricyclic systems containing thio-phene, cyclo-hexene and pyrrolidine rings (I) or furan, cyclo-hexene and pyrrolidine rings (II). The central cyclo-hexene 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 thio-phene (in I) or furan (in II) ring plane are 22.74 (16) and 26.29 (5)°, respectively. The nitro-gen 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 mol-ecules form hydrogen-bonded zigzag chains along [010] through strong inter-molecular O-H⋯O hydrogen bonds involving carb-oxy-lic and keto groups, whereas in the crystal of II, the mol-ecules are joined into centrosymmetric dimers by strong O-H⋯O hydrogen bonds between the carb-oxy-lic groups. In II, the atoms involved into these hydrogen bonds (and hence the whole carb-oxy-lic 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 enanti-omeric pairs of the 3aSR,4RS,4aRS,7aSR and 3aSR,4SR,4aRS,7aSR diastereomers, respectively.