The present invention relates to novel intermediates and a novel process for the preparation of antagonists of the NK1 subtype of tachykinin receptor. Specifically, the present invention provides novel intermediates and a novel process for the preparation of {2-[1-(3,5-bis-trifluoromethyl-benzyl)-5-pyridin-4-yl-1H-[1,2,3]triazol-4-yl]-pyridin-3-yl}-(2-chlorophenyl)-methanone, Form IV.
The compound {2-[1-(3,5-bis-trifluoromethyl-benzyl)-5-pyridin-4-yl-1H-[1,2,3]triazol-4-yl]-pyridin-3-yl}-(2-chlorophenyl)-methanone, depicted below as the compound of Formula I, was first described in PCT published application WO2003/091226.
Because the compound of Formula I is an antagonist of the NK-1 subtype of tachykinin receptor, it is useful for the treatment of disorders associated with an excess of tachykinins. Such disorders include depression, including major depressive disorder; anxiety, including generalized anxiety disorder, panic disorder, obsessive compulsive disorder, and social phobia or social anxiety disorder; schizophrenia and other psychotic disorders, including bipolar disorder; neurodegenerative disorders such as dementia, including senile dementia of the Alzheimer's type or Alzheimer's disease; disorders of bladder function such as bladder detrusor hyper-reflexia and incontinence, including urge incontinence; emesis, including chemotherapy-induced nausea and acute or delayed emesis; pain or nociception; disorders associated with blood pressure, such as hypertension; disorders of blood flow caused by vasodilation and vasospastic diseases, such as angina, migraine, and Reynaud's disease; hot flushes; acute and chronic obstructive airway diseases such as adult respiratory distress syndrome, bronchopneumonia, bronchospasm, chronic bronchitis, drivercough, and asthma; inflammatory diseases such as inflammatory bowel disease; gastrointestinal disorders or diseases associated with the neuronal control of viscera such as ulcerative colitis, Crohn's disease, functional dyspepsia, and irritable bowel syndrome (including constipation-predominant, diarrhea-predominant, and mixed irritable bowel syndrome); and cutaneous diseases such as contact dermatitis, atopic dermatitis, urticaria, and other eczematoid dermatitis.
In PCT published application, WO2005/042515, novel crystalline forms of the compound of Formula I, identified as Form IV and Form V, are identified. Also described in WO2005/042515 is a process for preparation of the compound of Formula I, comprising reacting (2-chlorophenyl)-[2-(2-hydroxy-2-pyridin-4-yl-vinyl)pyridin-3-yl]methanone or a phosphate salt thereof with 1-azidomethyl-3,5-bistrifluoromethylbenzene in the presence of a suitable base and a solvent. Use of this procedure results in several shortcomings for synthesis on a commercial scale. For example, use of the solvent DMSO, with (2-chlorophenyl)-[2-(2-hydroxy-2-pyridin-4-yl-vinyl)pyridin-3-yl]methanone phosphate, requires a complex work-up that has a propensity to emulsify. This process also requires extraction with CH2Cl2, the use of which is discouraged due to its potential as an occupational carcinogen, as well as the use of MgSO4 and acid-washed carbon, which can generate large volumes of waste on a commercial scale. Conducting the reaction with (2-chlorophenyl)-[2-(2-hydroxy-2-pyridin-4-yl-vinyl)pyridin-3-yl]methanone in isopropyl alcohol, as also described in WO2005/042515, is also undesirable due to the need to incorporate a free base step. Furthermore, variable levels of residual 1-azidomethyl-3,5-bistrifluoromethylbenzene, a known mutagen, are obtained from use of the procedures described in WO2005/042515.
An improved process for preparing the compound of Formula I would control the level of 1-azidomethyl-3,5-bistrifluoromethylbenzene impurity, and improve the yield. We have discovered that use of the novel salt, (2-chlorophenyl)-[2-(2-hydroxy-2-pyridin-4-yl-vinyl)pyridin-3-yl]methanone benzoate, as well as use of tert-butanol as the reaction solvent, improves reaction times and final yield, and decreases impurities in the final product. In addition, a novel process for the preparation of (2-chlorophenyl)-[2-(2-hydroxy-2-pyridin-4-yl-vinyl)pyridin-3-yl]methanone benzoate, in which a pre-formed enolate of 4-acetyl pyridine is added to (2-phenylsulfonyl-pyridine-3-yl)-(2-chlorophenyl)methanone, results in an overall improved yield and improved purity, and is useful on a commercial scale.