1-(3-Hydroxy-5,8-dimethoxy-4-methyl-1,2,3,4-tetrahydro-1,4-epoxynaphthalen-2-yl)ethan-1-one

The stereochemistry and regioschemistry (exo) of the title compound, C15H18O5, were determined by the X-ray analysis. The methoxy groups essentially lie in the plane of the benzene ring to which they are attached, as described by the C—O—C C torsion angles of −176.80 (12) and 4.67 (19)°. In the crystal, O—H⋯O hydrogen bonds and weak C—H⋯O hydrogen bonds link the molecules, forming chains of R 2 1(8) rings along [010].

The stereochemistry and regioschemistry (exo) of the title compound, C 15 H 18 O 5 , were determined by the X-ray analysis. The methoxy groups essentially lie in the plane of the benzene ring to which they are attached, as described by the C-O-C . . . C torsion angles of À176.80 (12) and 4.67 (19) . In the crystal, O-HÁ Á ÁO hydrogen bonds and weak C-HÁ Á ÁO hydrogen bonds link the molecules, forming chains of R 2 1 (8) rings along [010].

Structural commentary
We have previously investigated the metal-mediated cleavage of 2-isoxazoline rings fused to bicyclic frameworks that are prepared in our laboratory through nitrile oxide 1,3-dipolar cycloaddition methodology (Tranmer & Tam, 2002). When expanding this study using Raney Ni, cleavage of 2-isoxazoline compound (I) (see Fig. 1) leads to the formation of β-hydroxy ketone product (II) as a single stereoisomer. The stereochemistry of the product was determined by this singlecrystal X-ray analysis. Although different stereoisomers (exo and endo) could be formed, only the exo regioisomer (II) was formed.
The molecular structure of the title compound is shown in Fig. 2. The methoxy groups essentially lie in the plane of the benzene ring to which they are attached as described by the C15-O5-C12-C11 and C14-O4-C9-C10 torsion angles of -176.80 (12)

Synthesis and crystallization
To an oven dried flask containing the cycloadduct (I) (60 mg, 0.21 mmol) was added methanol (5 ml), THF (5 ml) and distilled water (2 ml) and the mixture was cooled to 273-278 K using an ice bath. AlCl 3 (87 mg, 0.65 mmol) was added to the cold solution in one portion and was stirred at 273 K for 15 minutes. Raney-nickel (0.52 g) was added and was stirred for 4 h at 273 K. The reaction mixture was filtered through a pad of celite, while washing with dichloromethane (20 ml). The organic layer was separated and the aqueous layer was extracted again with dichloromethane (10 ml), and the combined organic layers were dried over sodium sulfate then evaporated using rotary evaporation. The crude product was washed by hexanes (3 ml) followed by recrystallizaion in EtOAc:hexanes = 1:5 to give product (II) in 86% yield. Xray quality crystals were grown from a solution of the title compound in EtOAc:hexanes = 1:5.

Refinement
Hydrogen atoms bonded to C atoms were placed in calculated positions with C-H distances ranging from 0.95-1.00 Å and included in the refinement in a riding-model approximation with U iso (H) = 1.2U eq (C) or 1.5U eq (C methyl ). The hydroxyl H atom was refined independently with an isotropic displacement parameter. The reaction scheme.