5-Benzyl-7-methylhexahydro-3a,7-methano-1H-furo[3,4-c]azocine-3,10(4H)-dione

The title compound, C18H21NO3, was obtained via a double Mannich condensation reaction of 6-methyltetrahydroisobenzofuran-1,7(3H,7aH)-dione with formaldehyde and benzylamine. The molecule contains three fused rings of which the cyclohexanone and piperidine rings adopt chair conformations and the furanone ring assumes an envelope conformation. An intermolecular C—H⋯π interaction is present in the crystal structure.

The title compound, C 18 H 21 NO 3 , was obtained via a double Mannich condensation reaction of 6-methyltetrahydroisobenzofuran-1,7(3H,7aH)-dione with formaldehyde and benzylamine. The molecule contains three fused rings of which the cyclohexanone and piperidine rings adopt chair conformations and the furanone ring assumes an envelope conformation. An intermolecular C-HÁ Á Á interaction is present in the crystal structure.
Cg is the centroid of the phenyl ring.  (Guthmann et al., 2009;Coates et al., 1994;Barker et al., 2002) is an efficient method to append the E ring to the A ring. Therefore, we have designed and synthesized the racemic 1-substituted AE-bicyclic analogue by double Mannich condensation. Herein, we report the structure of the title compound.

D-HÁ
As illustrated in Fig. 1, the molecule of the title compound is constructed from the fusion of a cyclohexanone ring, a piperidine ring and a furanone ring. The two six-membered rings are in standard chair conformations. The furanone ring is cis-fused with the cyclohexanone ring and adopts envelope conformation. The bond angles around C4 and C5 are indicative of sp 2 hybridization for the two atoms. And the strain in the furanone ring is illustrated by the much distorted triangular geometry of C4 atom and the bond angles around C4 range between 109.7 (4) and 128.6 (5)°.
To a solution of 1b (200 mg, 1.19 mmol) in EtOH (300 mL) was added 37% CH 2 O solution (0.29 mL, 3.57 mmol) and phenylmethanamine (195 µL, 1.79 mmol). The reaction mixture was refluxing for 48 h and then concentrated under reduced pressure. The crude product was purified by flash column chromatography (ethyl acetate/hexane, v:v, 1:4) to give the title compound (107 mg, yield 30%) as a white solid. Crystallization from a ethyl acetate-petroleum ether system yielded colourless crystals suitable for single-crystal structure determination.

Refinement
H atoms were fixed geometrically and treated as riding, with C-H = 0.98 (methine), 0.97 (methylene), 0.96 (methyl) or 0.93 Å (aromatic) and U iso (H) = 1.5U eq (C) for methyl groups and U iso (H) = 1.2U eq (C) for the others. A total of 1163 Friedel pairs were merged before final refinement as there is no significant anomalous dispersion for the determination of the absolute configuration.  Fig. 1. The molecular structure of the title compound, showing the atom-numbering scheme with displacement ellipsoids at 30% probability level.