Sodium Carbonate → benzyl 3-(1-hydroxy-2-methoxy-2-oxoethyl)-2-methyl-4-(p-tolyl)-7,8-dihydro-1,6-naphthyridine-6(5H)-carboxylate

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A solution of benzyl 3-(2-methoxy-2-oxoacetyl)-2-methyl-4-(p-tolyl)-7,8-dihydro-1,6-naphthyridine-6(5H)-carboxylate (2.53 g, 5.52 mmol) (intermediate 10) and 1M (toluene) R-5,5-diphenyl-2-methyl-3,4-propano-1,3,2-oxazaborlidine (2.21 ml, 2.21 mmol) in toluene (100 ml) was cooled to −35° C. Catecholborane (50 wt % in toluene) (1.65 ml, 7.73 mmol) was added dropwise and the solution stirred at −35° C. for 30 min then at −15° C. for 2 h. The reaction was diluted with EtOAc and stirred vigorously with sat'd Na2CO3 for 1 h. The organic phase was washed with twice with satd Na2CO3, dried (Na2SO4), filtered and concentrated. The resulting oil was purified by flash column chromatography (Biotage; 0%-100% EtOAc/hexane) to provide benzyl 3-(1-hydroxy-2-methoxy-2-oxoethyl)-2-methyl-4-(p-tolyl)-7,8-dihydro-1,6-naphthyridine-6(5H)-carboxylate (1.29 g, 50% yield) as a white foam. 1H NMR (400 MHz, CDCl3) δ ppm 7.20-7.49 (m, 7H), 7.08 (t, J=8.68 Hz, 2H), 5.11 (d, J=15.65 Hz, 3H), 4.22 (br. s., 2H), 3.67-3.89 (m, 5H), 3.14 (d, J=2.45 Hz, 1H), 2.99-3.11 (m, 2H), 2.55 (s, 3H), 2.43 (s, 3H). LCMS (M+H) calcd for C27H29N2O5: 461.20. found: 461.0.

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