| 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(R2a)(R2b)C(O)Y (i.e. Formula II) wherein X and Y are leaving groups and L, R1, R2a and R2b 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, R8a, R8b, 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, R2a, R2b, 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 R2a and R2b are each H, and X and Y are each Cl then R1 is other than benzyl and when R2a and R2b 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(R2a)(R2b)CO2H (i.e. Formula VI) wherein R2a and R2b are H, X is Br and R1 is methyl.
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