Crystal structure of 3-iodo-5-methoxy-7-(methoxymethoxy)-4-(3-methoxyphenoxy)-2H-chromen-2-one, C₁₉H₁₇IO₇

Source of material

To a stirred water solution (30 mL) of sodium carbonate (1.06 g, 10.0 mmol) was added a THF solution (10 mL) of 4-hydroxy-5-methoxy-7-(methoxy)-2H-chromen-2-one (1.26 g, 5.0 mmol). After stirring at room temperature for 15 min, a THF solution (10 mL) of (3-methoxyphenyl)iodine (1.76 g, 5.0 mmol) was added and the stirring was continued for another 1 h. The reaction mixture was then filtered; the produced precipitant was collected, washed by water and dried in vacuum to afford the iodonium salt intermediate as light yellowish solid. The iodonium salt was then dissolved in DMF (10 mL), and the solution was refluxed for 1 h before the solvent was removed in vacuum. The crude product was purified by column chromatography (silica gel, PE/EtOAc, v/v, from 10/1 to 5/1), and the title compound (1.51 g, 63% over two steps) was yielded as white solid. Colorless crystals were obtained by slow evaporation of the column fraction at room temperature. IR (KBr, cm⁻¹): ν_{(lactone C = O)} 1718.93; ¹H NMR (400 MHz, DMSO-d₆, ppm): δ 7.19 (t, J = 8.2 Hz, 1.0 H), 6.74 (d, J = 2.2 Hz, 1.0 H), 6.64 (m, 1.0 H), 6.54 (t, J = 2.3 Hz, 1.0 H), 6.49 (d, J = 2.2 Hz, 1.0 H), 6.46 (m, 1.0 H), 5.31 (s, 2.0 H), 3.74 (s, 3.0 H), 3.47 (s, 3.0 H), 3.40 (s, 3.0 H). ¹³C NMR (101 MHz, DMSO-d₆, ppm): δ 163.21, 161.04, 160.53, 159.28, 156.73, 156.04, 155.97, 130.03, 107.83, 106.85, 101.49, 101.14, 96.82, 95.53, 94.03, 79.08, 56.16, 56.12, 55.28. HRMS (ESI): m/z C₁₉H₁₇IO₇ calcd [M]⁺ 484.0019, found [M + H]⁺ 485.0103.

Experimental details

All H atoms were placed at calculated positions with C—H distance in the range from 0.95 to 0.99 Å, and included in the final cycles of refinement using a riding model with U_iso(H) = 1.2U_eq(C, N) or U_iso(H) = 1.5U_eq(methyl C, O). Atoms C18, C19 and O7 of the MOM group appear disordered and occupy two positions (C18/C18′, C19/C19′ and O7/O7′) with occupancies of 0.723(5)/0.277(5)

Discussion

Coumarin derivatives are a class of compound that gains increasingly interest because of their variety of biological activities [1] and their importance as synthetic intermediates [2]. In spite of that the related structures of multi-substituted coumarin are extensively studied [3–5]. The molecular structure of the title compound has not been reported yet. In the present study, 3-iodo-5-methoxy-7-(methoxymethoxy)-4-(3-methoxyphenoxy)-2H-chromen-2-one was synthesized and structurally characterized by spectroscopic methods and crystal structure analysis, and both of the results are in good agreement with each other.

The asymmetric unit of the title compound consists of one molecule, which is comprised from a 10-membered chromene ring as the central core and substituents attach to it. The atoms of the central ring (C1—C9 and O1) and the ones directly link to it (O2, O3, O5, O6 and I1) are all co-planar. The bond lengths of I1—C2 (2.083 Å) and O2 = C1 (1.215 Å) are found to be in the expected range [6]. The methyl group links to O5 forms a 5.45° dihedron angle of C17—O5—C9—C8, and appears to be coplanar with the central core. The methoxymethyl connected to O6 shows twisted conformation. The 3-methoxy-phenyl group is attached to O3, and formed a diphenyl ether like conformation [7] with an angle of 89.33° between the two planes and 116.96° for the angle of C3—O3—C10.

The chromene rings of the two adjacent molecules are pairwise parallel to each other with a distance of 3.533 Å, and intermolecular π−π stacking interaction is observed between them.