Synthesis and Spatial Structure of (E)-1-(2-(4-Bromobutoxy)- 6-Hydroxy-4-Methoxyphenyl-3-Phenylprop-2-en-1-one

Abstract

(E)-1-(2-(4-bromobutoxy)-6-hydroxy-4-methoxyphenyl-3-phenylprop-2-en-1-one was synthesized from the pinostrobin molecule. The tetrahydropyran cycle was opened in acetone under heating (50–60 °C) mixtures of components for 16 hours in the presence of 3 moles of K2CO3 and 1,4-dibromobutane. The resulting sub-stance is a yellow powder of the composition C20H21BrO4, mp 83.7–86.6 °C. The structure of the obtained compound was established on the basis of the data of elemental analysis, IR and NMR spectra. As a result of X-ray diffraction analysis, it was found that the hydrogen atoms in the C8=C9 bond take the trans-conformation. The rotation of the С1…С6 phenyl ring (flat with an accuracy of ±0.008 Å) relative to the С10…С15 cycle (flat with an accuracy of ±0.004 Å) is 14.3°. In the crystal, the molecules are linked by an intramolecular hydrogen bond O4-H....O1 (distances O-H 0.95(8) Ǻ, O····O 2.469(6) Ǻ, H····O 1.58 (8) Ǻ, angle O-H····O 153(7)°). The formation of (E)-1-(2-(4-bromobutoxy)-6-hydroxy-4-methoxy-1-phenylprop-2-en-1-one can be explained by the ease of the retro-Michael reaction of the pyran ring and the subsequent O-alkylation of the resulting chalcone. Carrying out the reaction in the presence of other bases (cesium car-bonate, triethylamine) did not lead to success. The starting substance (pinostrobin) was completely converted into oligomeric compounds.