Process for the preparation of polymorphs of imidacloprid

摘要

A process for the preparation of a Form I crystalline polymorph of imidacloprid, including: (i) dissolving imidacloprid in an appropriate amount of aqueous solvent or mixture of solvents to obtain an aqueous solution; (ii) cooling the aqueous solution slowly, thereby forming crystals of polymorph Form I of imidacloprid; (iii) isolating the crystals. A process for the preparation of a Form II crystalline polymorph of imidacloprid, comprising: dissolving imidacloprid in an appropriate amount of non-aqueous solvent or mixture of non-aqueous solvents to obtain a non-aqueous solution; (ii) cooling the solution rapidly, thereby forming crystals of polymorph Form II of imidacloprid; (iii) isolating the crystals.

主权项

1. A process for the preparation of a Form II crystalline polymorph of imidacloprid exhibiting an X-ray powder diffraction pattern having characteristic peaks (expressed in degrees 2θ+/−0.2°θ) at one or more of the following positions: 4.580, 13.780, 18.420, 18.880 and 23.120, or exhibiting a Differential Scanning calorimetry (DSC) thermogram which is characterized by a predominant endotherm peak at about 136.5° C., or both, comprising:
(i) dissolving imidacloprid in an amount of non-aqueous solvent or mixture of non-aqueous solvents appropriate to obtain a non-aqueous solution, wherein the non-aqueous solvent is selected from the group consisting of methanol, ethanol, tetrahydrofuran, acetonitrile, methylene chloride, isopropyl alcohol, acetone, N,N-dimethyl-formamide, dimethyl sulfoxide, toluene, benzene, n-hexane, petroleum ether, ethyl acetate, ether, dichloromethane, chloroform, and carbon tetrachloride; (ii) cooling the solution rapidly, thereby forming crystals of polymorph Form II of imidacloprid; (iii) isolating the crystals.