Lithium Chloride → 6-((Benzyloxy)carbonyl)-2-methyl-4-(p-tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridine-3-carboxylic acid

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Reaction Conditions

Reaction Steps

A mixture of 6-benzyl 3-methyl 2-methyl-4-(p-tolyl)-7,8-dihydro-1,6-naphthyridine-3,6(5H)-dicarboxylate (intermediate 10) (0.482 g, 1.12 mmol) and lithium chloride (0.475 g, 11.19 mmol) in 2,6-lutadine (10 mL) and DMSO (10.00 mL) was stirred at 130° C. for 2 h. The mixture was cooled to room temperature, diluted with water and extracted with EtOAc to remove unreacted starting material and impurities. The aqueous phase was made acidic with 1N HCl and extracted with EtOAc (2×'s) then CH2Cl2. The organic extracts were combined, dried (Na2SO4), filtered and concentrated to provide 6-((benzyloxy)carbonyl)-2-methyl-4-(p-tolyl)-5,6,7,8-tetrahydro-1,6-naphthyridine-3-carboxylic acid (74.2 mg, 15% yield) as an amber oil. 1H NMR (400 MHz, CDCl3) δ ppm 7.33 (br. s., 4H), 7.24 (d, J=7.83 Hz, 3H), 7.13 (d, J=7.58 Hz, 2H), 5.11 (s, 2H), 4.36 (s, 2H), 3.78 (t, J=5.62 Hz, 2H), 3.30 (br. s., 2H), 2.80 (br. s., 3H), 2.38 (s, 3H). LCMS (M+H) calcd for C25H25N2O4: 417.18. found: 417.4.

Provenance & Evidence