Crystal structure of ethyl 2-(di­eth­oxy­phosphor­yl)-2-(2,3,4-tri­meth­oxy­phen­yl)acetate

The title compound, C₁₇H₂₇O₈P, was prepared by Michaelis–Arbuzov reaction of ethyl 2-bromo-2-(2,3,4-tri­meth­oxy­phen­yl)acetate and triethyl phosphite. Such compounds rarely crystallize, but single crystals were recovered after the initial oil was left for approximately 10 years. The bond angle of the sp³-hybridized C atom connecting the benzene derivative with the phospho unit is widened marginally [112.5 (2)°]. The terminal P—O bond length of 1.464 (2) Å clearly indicates a double bond, whereas the two O atoms of the eth­oxy groups connected to the phospho­rous atom have bond lengths of 1.580 (2) Å and 1.581 (3) Å. The three meth­oxy groups emerge out of the benzene-ring plane due to steric hindrance [C—C—O—C torsion angles = −179.9 (3)°, −52.9 (4)° and 115.3 (4)°]. In the crystal, inversion dimers linked by pairs of C—H...O=P hydrogen bonds generate R₂²(14) loops. The chosen crystal was modelled as a non-merohedral twin.