(2E)-Methyl 2-(7-benzyloxy-1-naphthyl)-3-methoxyacrylate

In the title compound, C22H20O4, the dihedral angle between the phenyl and naphthalene ring systems is 86.10 (10)°. The methoxyacrylate group is disordered over two orientations in a 0.905 (3):0.095 (3) ratio.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: ZQ2038).

Comment
Ether compounds containing aromatic rings are present in many bioactivity compounds and are useful intermediates in organic synthesis (Kozikowski et al., 2000;Gunatilaka, 2006). Methylene carbonyl compounds have been studied extensively in recent years, since they are not only useful as synthetic intermediates but also often found in biologically active natural compounds (Gotthardt et al., 1978;Shono et al., 1979). Here we report the synthesis and the crystal structure of the title compound C 22 H 20 O 4 , namely (E)-methyl 2-(7-(benzyloxy)naphthalen-1-yl)-3-methoxyacrylate (I).
In the crystal structure, the molecule of (I) adopts two different conformations according to the relative position of the methoxyacrylate group. The minor and major conformers could be distinguished by the disorder of the oxygen atom O2 of the carbonyl group which occupies two different sites A (bound to C19) and B (bound to C21), the refined site-occupancy factors are 0.905 (3) and 0.095 (3), respectively. The naphthalene and benzene rings are essentially planar with r.m.s. deviations of 0.0036 (14) Å and 0.0001 (3) Å, respectively. The phenyl ring is almost perpendicular to the naphthalene ring, the dihedral angle between them is 86.10 (10)°, which is different from that in methyl 2-(7-benzyloxy-1-naphthyl)-2-oxoacetate, of 43.78 (7)° (Fun et al., 2008). The dihedral angle between the mean plane of the methoxyvinyl and methoxycarbonyl groups is only 6.47 (18)°. The latter long and almost planar substituent plays an important role in the whole folded conformation of (I). Nevertheless, no classic hydrogen bonds were found in the crystal structure.
To a solution of methyl 2-(7-benzyloxy-1-naphthyl)-2-oxoacetate (4 g, 12.5 mmol) in dry THF (10 ml) was slowly added an excess of (methoxymethyl)triphenylphosphonium chloride (5.1 g, 20 mmol) in dry ether and 2.5 M butyl lithium in hexane (6 ml) under nitrogen. The mixture was allowed to warm to room temperature for 24 h, and then was quenched with dilute hydrochloric acid. The crude product was purified by column chromatography with petroleum ether -ethyl acetate (5: 1) as the eluent, to afford I as a white powder (0.5 g, 11.9%). Single crystals suitable for a X-ray analysis were obtained by slow evaporation from ethanol at room temperature for several days (m.p. 125-126°C).

Refinement
All H atoms were positioned geometrically and refined as riding atoms, with C-H = 0.93Å and U iso = 1.2U eq (C) for aromatic hydrogen atoms, with C-H = 0.97 Å and U iso = 1.2U eq (C) for methylene hydrogen atoms, and with C-H=0.96 Å and U iso = 1.5U eq (C) for methyl hydrogen atoms. The minor and major conformers could be distinguished by the disorder of the oxygen atom O2 of the carbonyl group which occupies two different sites A (bound to C19) and B (bound to C21), the refined site-occupancy factors are 0.905 (3) Fig. 1. The molecular structure of (I) showing 30% probability displacement ellipsoids and the atomic numbering.