Preparation and use of 2-substituted-5-oxo-3-pyrazolidinecarboxylates

摘要

A method is disclosed for preparing a 2-substituted-5-oxo-3-pyrazolidinecarboxylate compound of Formula I. The method comprises contacting a succinic acid derivative of the formula R¹OC(O)C(H)(X)C(R^2a)(R^2b)C(O)Y (i.e. Formula II) wherein X and Y are leaving groups and L, R¹, R^2a and R^2b are as defined in the disclosure, with a substituted hydrazine of the formula LNHNH₂ (i.e. Formula III) in the presence of a suitable acid scavenger and solvent. Also disclosed is the preparation of compounds of Formula IV wherein X¹, R⁶, R⁷, R^8a, R^8b, R⁹, and n are as defined in the disclosure. Also disclosed is a composition comprising on a weight basis about 20 to 99% of the compound of Formula II wherein R¹, R^2a, R^2b, R³, R⁴ and R⁵ are as defined in the disclosure; X is Cl, Br or I; and Y is F, Cl, Br or I; provided that when R^2a and R^2b are each H, and X and Y are each Cl then R¹ is other than benzyl and when R^2a and R^2b are each phenyl, and X and Y are each Cl, then R¹ is other than methyl or ethyl. Also disclosed is a crystalline composition comprising at least about 90% by weight of the compound of the formula R¹OC(O)C(H)(X)C(R^2a)(R^2b)CO₂H (i.e. Formula VI) wherein R^2a and R^2b are H, X is Br and R¹ is methyl.