Dimethylamine → 6-(3-Chloro-4-fluorobenzyl)-4-methoxy-N,N,2-trimethyl-3,5-dioxo-2,3,5,6,7,8-hexahydro-2,6-naphthyridine-1-carboxamide

Participants

Reaction Conditions

Reaction Steps

To a suspension of 6-(3-chloro-4-fluorobenzyl)-4-methoxy-2-methyl-3,5-dioxo-2,3,5,6,7,8-hexahydro-2,6-naphthyridine-1-carboxylic acid (8.50 g, 22 mmol) in methylene chloride (300 mL) at 0° C. was added oxalyl chloride (2.25 mL, 26 mmol) and 1 drop of anhydrous DMF. The reaction was stirred at 0° C. for 15 minutes during which time no bubbling was observed. The reaction was then allowed to warm to room temperature and stirred for 40 minutes. At this time bubbling had ceased, and all material was in solution. An aliquot of the solution was quenched with dimethylamine and checked by LCMS to confirm completion. To the solution of the acid chloride starting material at 0° C. was added dimethylamine in THF (43.56 mL, 87 mmol, 2.0 M). The green/yellow reaction was allowed to stir at room temperature overnight although the reaction appeared to proceed immediately by LCMS. The solvent was removed in vacuo, and the resulting residue was dissolved in chloroform. The solution was washed with water and 5% aqueous HCl solution and back extracted to recover the product. The combined organic layers were washed with brine, dried over sodium sulfate, filtered and concentrated in vacuo. The resulting iridescent green/yellow residue was examined in several TLC solvent systems (95:5 CH2Cl2:MeOH, 2:1 acetone:hexanes, 1:1 EtOAc:hexanes) with the most efficient separation of some early running impurities achieved in the CH2Cl2:MeOH system. The material was purified by silica gel flash column chromatography, loaded as a solution in methylene chloride onto a 330 g RediSep column. Gradient elution consisted of 1.5 L each of neat CH2Cl2, 1% MeOH:CH2Cl2, 2% MeOH:CH2Cl2, 3% MeOH:CH2Cl2, 4% MeOH:CH2Cl2, and 5% MeOH:CH2Cl2, in sequential order. The desired material began to elute with 3% and was pushed off the column with 4% and 5%, yielding two sets of fraction. The earlier set afforded of the desired product plus a fluorescent green contaminant. The later set afforded clean material.

Provenance & Evidence