An efficient synthesis of a structurally unique, novel M(3) antagonist 1 is described. Compound 1 is conveniently disconnected retrosynthetically at the amide bond to reveal the acid portion 2 and the amine fragment 3. The synthesis of key intermediate 2 is highlighted by a ZnCl(2)-MAEP complex 19 catalyzed diastereoselective Michael reaction of dioxolane 7 with 2-cyclopenten-1-one (5) to establish the contiguous quaternary-tertiary chiral centers and a subsequent geminal difluorination of ketone 17 using Deoxofluor in the presence of catalytic BF(3).OEt(2). The synthesis of the amine moiety 3 is highlighted by the discovery of a novel n-Bu(3)MgLi magnesium-halogen exchange reaction for selective functionalization of 2,6-dibromopyridine. This new and practical metalation protocol obviated cryogenic conditions and upon quenching with DMF gave 6-bromo-2-formylpyridine (26) in excellent yield. Further transformations afforded the amine fragment 3 via reductive amination with 35, Pd-catalyzed aromatic amination, and deprotection. Finally, the highly convergent synthesis of 1 was accomplished by coupling of the two fragments. This synthesis has been used to prepare multi-kilogram quantities of the bulk drug.

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A concise and practical synthesis of a 1,4-diaryl-5-methyl-1,2,3-triazole is described. A mGluR1 antagonist 1 was prepared with one-pot operation by the Negishi coupling reaction between two building blocks, 5-bromophthalimidine (2) and 1-aryl-5-methyl-4-triazolylzinc (3-Zn ). Bromide 2 was synthesized via N-selective cyclization of o-hydroxymethylbenzamide 8 easily prepared from phthalide 4. Zinc species 3-Zn was generated in situ by transmetalation of 1-aryl-4-magnesio-5-methyltriazole (3-Mg ), which in turn was generated by the regioselective click chemistry between 2,4-difluorophenylazide (5) and propynylmagnesium bromide. The risk assessment of potentially explosive arylazides is also mentioned.