G. Khan, N. H. Rama, G. Qadeer
2006
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Zeitschrift für Kristallographie - New Crystal Structures
Abstract
C13H16O6, triclinic, P1 (no. 2), a = 7.343(2) Å, b = 8.972(2) Å, c = 10.152(2) Å, / = 81.12(2)°, 0 = 77.997(2)°, " = 80.22(2)°, V = 639.8 Å, Z = 2, Rgt(F) = 0.081, wRref(F) = 0.239, T = 191 K. Source of material Phosphorus oxychloride (5.3 g, 0.034mol) was added dropwise to a stirred solution of methyl 3,4,5-trimethoxyphenylacetate (7 g, 0.029mol) in freshly distilledN,N-dimethylformamide (30ml) at 550 °C.The solutionwas then heated at 100 °C for 10minutes and stirred overnight. The reaction mixture was poured into aqueous sodiumacetate (10%, 300ml)with stirring.The resultant precipitate was recrystallized from ethyl acetate to yield methyl 2-formyl-3,4,5-trimethoxyphenylacetate (4.5 g, 0.0168 mol) as colorless crystals suitable for the X-ray single-crystal structure analysis. Experimental details The large R values are caused by the slightly poor quality of the crystals. Solvent molecules were not found in the structure.Only theH1atom (atC10) was refined due its importance in the hydrogen bonding,while the otherH atomswere added geometrically. Discussion The reported compound known as methyl 2-formyl-3,4,5-trimethoxyphenyl-acetate is the intermediate for the synthesis of naturally occurring biological active isocoumarins and 3,4-dihydroisocoumarins. The most important naturally occurring isocoumarins synthesized by the title compound is (+)-kigelin [1]. In the title crystal structure, the bonds lengthswithin phenyl ring lie between 1.383(3)Å and 1.410(2)Åwhich highlights the aromatic character. The valence angle C2–C3–C4 (121.7(2)°) is larger than the standard value of 120°.The opening of this angle is due to the presence of the twomethoxy and one formyl groups onC2,C3 andC4, respectively, which involves a decrease of the ring angles ofC1 (119.5(2)°) andC4 (118.5(2)+).TheC10—O4 (1.202(3)Å) and C12—O6 (1.336(2) Å) bond distances are compatible with respective distances in related structures [2-4] and smaller than those usually observed in carboxylic acids (1.365 Å). The structure is influenced by intraand intermolecular hydrogen bonding. The formyl H atom forms an intramolecular bond to the corresponding methoxy O atoms, i.e. C–H···O (d(H1···O3) = 2.279 Å. The crystal structure is stabilized by intermolecular C–H···O hydrogen bonds, whereas the formylH atom of a moleculeA interactswith theO atomof the ester group of the neighboringmolecule B (d(H10A···O5B) = 2.689 Å) and the H atom of the ester group of themoleculeB interactswith theO atomof the formyl group of the moleculeA (d(H13B···O4A) = 2.628Å). Simultaneously, the ester group present onmoleculeA interactswith the formyl group of another neighboring molecule C in a quite similar fashion. Z. Kristallogr. NCS 221 (2006) 497-498 / DOI 10.1524/ncrs.2006.0171 497 © by OldenbourgWissenschaftsverlag,München Crystal: colorless needle, size 0.46 × 0.45 × 0.70 mm Wavelength: Mo K/ radiation (0.71069 Å) %: 1.11 cm−1 Diffractometer, scan mode: Stoe IPDS II, ) 2'max: 51.36° N(hkl)measured, N(hkl)unique: 8287, 2372 Criterion for Iobs, N(hkl)gt: Iobs > 2 ((Iobs), 2175 N(param)refined: 176 Programs: SIR97 [5], SHELXL-97 [6] Table 1. Data collection and handling. H(17) 2i 0.1349 0.1774 0.3921 0.033 H(19A) 2i 0.2183 0.2775 0.0415 0.078 H(19B) 2i 0.0967 0.3021 0.1888 0.078 H(19C) 2i 0.2082 0.1374 0.1601 0.078 H(10A) 2i 0.7643 0.5019 0.1067 0.064 H(10B) 2i 0.6258 0.5504 0.2420 0.064 H(10C) 2i 0.5468 0.4821 0.1319 0.064 H(8A) 2i 0.9170 0.4049 0.5163 0.061 H(8B) 2i 0.6969 0.4660 0.5516 0.061 H(8C) 2i 0.7980 0.4531 0.3973 0.061 H(16A) 2i 0.1863 −0.0119 0.6949 0.035 H(16B) 2i 0.0346 0.0602 0.6019 0.035 H(18A) 2i −0.2737 0.1174 1.0243 0.070 H(18B) 2i −0.2810 0.2719 0.9218 0.070 H(18C) 2i −0.1155 0.2251 1.0074 0.070 H(1) 2i 0.615(4) 0.160(3) 0.717(3) 0.048(7) Table 2. Atomic coordinates and displacement parameters (in Å). Atom Site x y z Uiso