434952-87-1

Upstream product

• 169544-41-6 4-(4-chlorophenyl)-3-methyl-2,4-dioxobutyric acid ethyl ester 
• 13123-92-7 (2,4-dichlorophenyl)hydrazine 
• 1012314-40-7 ethyl 4-(4-chlorophenyl)-3-methyl-4-oxydo-2-oxobuten-3-oate lithium salt 
• 5446-18-4 2,4-dichlorophenyl hydrazine hydrochloride 
• 6285-05-8 4'-chloropropiophenone 

Downstream Products

• 158941-22-1 ethyl 1-(2,4-dichlorophenyl)-4-methyl-5-(4-chlorophenyl)-1H-pyrazole-3-carboxylate 
• 162758-35-2 rimonabant acid 

Relevant academic research and scientific papers

Tritiation of SR141716 by metallation-iodination-reduction: Tritium-proton nOe study

The central cannabinoid receptor antagonist SR141716, N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2, 4-dichlorophenyl)-4-methyl-1 H-pyrazole-3-carboxamide, was synthesized from commercially available starting materials. Condensation of an aryl hydrazine with a diketone followed by base promoted isomerization/cyclization of the intermediate anti-imine gave the pyrazole acid which was converted to the title hydrazide via its acid chloride. Facile iodination via metallation followed by in situ trapping with an iodine source gave a modest yield of the iodinated SR 141716. The iodine was selectively reduced with tritium gas and catalyst while retaining the three aryl chlorine atoms in the structure. The tritiated SR 141716 exhibited a tritium-proton nOe both definitively identifying the position of the tritium as well as the sought isomer of the diarylpyrazole. This work provides a direct method for the preparation of preferred iodinated aryl substrates that offer advantages where selectivity and high incorporation in catalytic reduction is sought. Copyright

IMPROVED PROCESS FOR RIMONABANT

The present invention provides an improved and commercially viable process for the preparation of rimonabant substantially free of amide impurity, namely 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl-4-methyl-pyrazole-3-carboxamide and its pharmaceutically acceptable acid addition salts thereof. Thus, for example, 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl-4-methyl-pyrazole-3-carboxylic acid chloride is reacted with 1-minopiperidine in the presence of a base and optionally using a phase transfer catalyst such as tetra-butylammonium bromide in a biphasic reaction medium containing water and a water-immiscible solvent to obtain pure rimonabant.

Synthesis, Spectral Studies and Tritiation of the Cannabinoid Antagonist SR141716A

An efficient synthesis of the cannabinoid antagonist SR141716A is presented and the structure is established by nOe experiments; tritiated SR141716A is synthesized by a novel sequence of metallation-iodination-tritiation and the labelled site is shown by tritium NMR and tritium-hydrogen nOe experiments.