1,2,3,5-Tetrahydronaphtho[2,1-c]oxepine

In the title compound, the seven-membered ring is in a psuedo-chair conformation. In the crystal, molecules are linked by weak C—H⋯O hydrogen bonds forming layers parallel to (010). In addition, there are weak π–π stacking interactions between inversion-related naphthalene ring systems.


Structure description
In past years, our research group has investigated the ring-opening reactions of cyclopropanated oxabenzonorbornadienes (CPOBD) (Carlson et al., 2014(Carlson et al., , 2016(Carlson et al., , 2018Tait et al., 2016;Tigchelaar et al., 2014). Recently, we have examined the intramolecular ringopening of reaction of CPOBD with tethered alcohol nucleophiles (Wicks et al., 2019). Based on previous work done in our research group, we anticipated two possible modes of ring-opening through nucleophilic attack at either the proximal or distal cyclopropyl carbon atom. Reaction of the C 1 -alcohol tethered CPOBD I (see Fig. 3) in the presence of p-TsOHÁH 2 O in toluene afforded the Type 2 II and Type 3 III ring-opened products in 12% and 59% yields, respectively. The title structure of the Type 2 (II) regioisomer was verified by single-crystal X-ray analysis.

Synthesis and crystallization
To a 6 dram vial open to air were added the alcohol-tethered cyclopropanated oxabenzonorbornadiene I (0.3547 g, 1.64 mmol), and p-TsOHÁH 2 O (57.7 mg, 20 mol%) data reports dissolved in 7 ml of toluene (see Fig. 3). The reaction was left to stir at 333 K for 1.5 h, after which the reaction mixture was cooled and quenched with 10 ml of water. The aqueous layers were combined and back extracted with EtOAc (3 Â 5 ml). The organic layers were combined, washed with brine, dried over MgSO 4 , and concentrated in vacuo. The resulting crude oil was purified by flash chromatography (EtOAc:hexanes, 10: 90) to obtain ring-opened products II (38.5 mg, 0.194 mmol, 12%) and III (189.8 mg, 0.957 mmol) as a white solid and clear oil, respectively. The title compound II was subsequently crystallized from DCM solution by slow evaporation of the solvent to afford colourless blocks.

Figure 2
Part of the crystal structure with weak hydrogen bonds shown as dashed lines. Only H atoms involved in hydrogen bonds are shown.

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level.

Figure 3
The reaction scheme.  Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.