Reaction of phosphorus pentachloride with 4-methyl-1,1,1-trichloro-4-penten-2-ol

Abstract

Phosphorylation of alkenols with phosphorus pentachloride has not been studied so far. We first studied behavior in this reaction of 4-methyl-1,1,1trichloro-4-pentene-2-ol (I), an intermediate in the industrial synthesis of a piretroid preparation permetrin. The process was carried out using an inert organic solvent (benzene, carbon tetrachloride or toluene) under mild conditions (0–5°C). We found that at equimolar reagent ratio occurs O-phosphorylation of alcohol I. By the data of IR spectroscopy and Н and P NMR spectroscopy, the reaction product is 4methyl-1,1,1-trichloropent-4-en-2-yl dichlorophosphate (II) (δP 10 ppm). At higher amount of phosphorus pentachloride occurred intermediate formation of crystalline adduct (i1) that we separated and treated with acetone at 5–10°C. Study of the reaction products by the method of P NMR spectroscopy showed that at the ratio of the reagents 3:1 the product of Cposphorylation (δP 44 ppm) is only formed. By the data of IR spectroscopy, it contains a double bond (ν 1655 cm), a dichlorophosphoryl group [ν(P=O) 1260 cm, ν(P–Cl) 585, 545 cm] and a trichloromethyl group (ν 790 cm). In the Н NMR spectrum occurs a doublet at δ 3.79 ppm, JPH 19 Hz characteristic of PCН2 group, a doublet of methyl protons at δ 2.41 ppm, JPH 5 Hz, and a multiplet at δ 5.44–6.27 ppm, corresponding to the region of ethylene and chloromethine protons. Together with the data of elemental analysis, this allowed to propose for the synthesized compound the structure of 2-methyl4,5,5,5-tetrachloropent-2-ene-1-phosphonic acid (III), that does not contradict to the data [1, 2]. DOI: 10.1134/S1070363208100320