Process for the preparation of alkyl 3-difluoromethyl-1-methyl-1H-pyrazole-4-carboxylate and its analogs
US9139507B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 9, 2013 |
| Grant date | Sep 22, 2015 |
| Priority date | — |
| Expiry date | Dec 9, 2033 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC07C67/54
- WIPO fieldOrganic fine chemistry
- WIPO sectorChemistry
Abstract
The disclosure provides a process for the preparation of alkyl 3-difluoromethyl-1-methyl-1H-pyrazole-4-caboxylate and its analogs. The process includes a reaction workup method for Claisen condensation, wherein the enolate salt is acidified after removing remaining starting material and byproducts such as, ethanol and excessive ethyl acetate. The process also includes a method for completely drying alkyl difluoroacetoacetate and its analogs before use in the next step by reacting trialkyl orthoformate with the residual water. The process includes using Na2CO3 and/or K2CO3 to promote the ring-closure reaction to produce the alkyl 3-difluoromethyl-1-methyl-1H-pyrazole-4-carboxylate. The process also includes effectively removing the regioisomer, alkyl 3-difluoromethyl-2-methyl-1H-pyrazole-4-caboxylate formed as a byproduct of the ring closure by a precipitation in a mixed solvent system and thereby eliminating the need for recrystallization of the final product.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.