Benzyl chloroformate → Benzyl 2-methyl-4-oxo-3,4-dihydropyridine-1(2H)-carboxylate

Reaction equation

C[O:2][C:3]1[CH:8]=[CH:7][N:6]=[CH:5][CH:4]=1.[CH3:9][Mg]Cl.[CH2:12]([O:19][C:20](Cl)=[O:21])[C:13]1[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=1>O1CCCC1>[CH3:9][CH:7]1[CH2:8][C:3](=[O:2])[CH:4]=[CH:5][N:6]1[C:20]([O:19][CH2:12][C:13]1[CH:18]=[CH:17][CH:16]=[CH:15][CH:14]=1)=[O:21]

Participants

Procedure

The methodology of D. L. Comins and J. D. Brown, Tetrahedron Letters, 1986, pp 4549-4552 was used: To a stirred solution of 2.5 g of 4-methoxypyridine in 75 mL of anhydrous tetrahydrofuran cooled to -23° C. under a nitrogen atmosphere was added 8 mL of 3M methylmagnesium chloride in tetrahydrofuran followed by 4 g of benzylchloroformate, keeping the internal temperature below -20° C. After stirring for 4 h at -25°±5° C., the reaction was quenched with 100 mL of 1N HCl and extracted with 5×100 mL portions of ether. The combined extracts were dried over MgSO4 and concentrated under reduced pressure. Further drying under vacuum gave 5.1 g of 2(R,S)-methyl-1-(benzyloxycarbonyl)-2,3-dihydro-4-pyridone as a greenish oil: TLC (25% EtOAc in hexane); 1H NMR (400 MHz, CDCl3) 7.75 (d, 1H), 7.4 (s, 5H), 5.30 (d, 1H), 5.26 (s, 2H), 4.7 (m, 1H), 2.82 (dd, 1H), 2.38 (d, 2H), 1.25 (t, 3H).