Treatment of 5-bromo-3-pyridinecarboxylic acid (I) with thionyl chloride in 1,2-dichloroethane (DCE) gives acid chloride hydrochloride (II), which is converted to ester (III) on treatment with ethanol in DCE. Claisen condensation of ester (III) with N-vinylpyrrolidinone (IV) in the presence of littium bis(trimethylsilyl)amide followed by refluxing in aqueous hydrochloric acid gives the pyrroline (V). The reduction of pyrroline (V) with sodium borohydride in the presence of the chiral auxiliary N-carbobenzyloxy-L-proline yields the enantiomerically enriched (S)-pyrrolidine (VI) with an e.e. of 30%. This compound is reductively methylated in a mixture of aqueous formaldehyde and formic acid, and the resulting N-methylpyrrolidine (VII) is converted to the di-p-toluoyl-D-tartaric acid salt, and recrystallized from ethanol-ethyl acetate to increase the e.e. to 90%. The free amine (VII) is coupled with trimethylsilyl acetylene (VIII), in the presence of bis(triphenylphosphine)palladium dichloride, cuprous iodide, and triethylamine in THF. The resulting compound (IX) is treated with cesium carbonate in refluxing methanol to remove the trimethylsilyl group, and finally converted to the maleate salt on treatment with maleic acid in methanol.

Treatment of 5-bromo-3-pyridinecarboxylic acid (I) with thionyl chloride in 1,2-dichloroethane (DCE) gives acid chloride hydrochloride (II), which is converted to ester (III) on treatment with ethanol in DCE. Claisen condensation of ester (III) with N-vinylpyrrolidinone (IV) in the presence of littium bis(trimethylsilyl)amide followed by refluxing in aqueous hydrochloric acid gives the pyrroline (V). The reduction of pyrroline (V) with sodium borohydride in the presence of the chiral auxiliary N-carbobenzyloxy-L-proline yields the enantiomerically enriched (S)-pyrrolidine (VI) with an e.e. of 30%. This compound is reductively methylated in a mixture of aqueous formaldehyde and formic acid, and the resulting N-methylpyrrolidine (VII) is converted to the di-p-toluoyl-D-tartaric acid salt, and recrystallized from ethanol-ethyl acetate to increase the e.e. to 90%. The free amine (VII) is coupled with trimethylsilyl acetylene (VIII), in the presence of bis(triphenylphosphine)palladium dichloride, cuprous iodide, and triethylamine in THF. The resulting compound (IX) is treated with cesium carbonate in refluxing methanol to remove the trimethylsilyl group, and finally converted to the maleate salt on treatment with maleic acid in methanol.

Treatment of 5-bromo-3-pyridinecarboxylic acid (I) with thionyl chloride in 1,2-dichloroethane (DCE) gives acid chloride hydrochloride (II), which is converted to ester (III) on treatment with ethanol in DCE. Claisen condensation of ester (III) with N-vinylpyrrolidinone (IV) in the presence of littium bis(trimethylsilyl)amide followed by refluxing in aqueous hydrochloric acid gives the pyrroline (V). The reduction of pyrroline (V) with sodium borohydride in the presence of the chiral auxiliary N-carbobenzyloxy-L-proline yields the enantiomerically enriched (S)-pyrrolidine (VI) with an e.e. of 30%. This compound is reductively methylated in a mixture of aqueous formaldehyde and formic acid, and the resulting N-methylpyrrolidine (VII) is converted to the di-p-toluoyl-D-tartaric acid salt, and recrystallized from ethanol-ethyl acetate to increase the e.e. to 90%. The free amine (VII) is coupled with trimethylsilyl acetylene (VIII), in the presence of bis(triphenylphosphine)palladium dichloride, cuprous iodide, and triethylamine in THF. The resulting compound (IX) is treated with cesium carbonate in refluxing methanol to remove the trimethylsilyl group, and finally converted to the maleate salt on treatment with maleic acid in methanol.

The reaction of 5-bromopyridine-3-carboxylic acid (I) with (COCl)2 and CuI in DMF gives the acyl chloride (II), which is reduced with LiAlH(O-tBu)3 in THF to yield the carbaldehyde (III). The allylation of (III) with the organozinc bromide (IV) in THF affords 1-(5-bromo-3-pyridyl)-3-buten-1-ol (V), which is oxidized with DMP in dichloromethane to provide the corresponding ketone (VI). The enantioselective reduction of (VI) with (+)-B-chlorodiisopinocampheyl borane ((+)-DIP-Cl) in ether gives the (R)-enantiomer (VII), which is treated with Ms-Cl and TEA in dichloromethane to yield the mesylate (VIII). The reaction of (VIII) with sodium azide in DMF affords the (S)-azide (IX), which is finally submitted to a reductive cyclization by means of dicyclohexylborane (Cy2BH) in THF to afford the target 3-bromo-5-(2(S)-pyrrolidinyl)pyridine (X) intermediate (see scheme no. 22999801a, intermediate (VI)).