C(Cl)Cl.[N+:4]([C:7]1[CH:8]=[C:9]([OH:13])[CH:10]=[CH:11][CH:12]=1)([O-:6])=[O:5].[CH3:14][C:15]([CH3:20])([CH3:19])[C:16](Cl)=[O:17].[NH4+].[Cl-]>CN(C1C=CN=CC=1)C.N1C=CC=CC=1>[C:16]([O:13][C:9]1[CH:10]=[CH:11][CH:12]=[C:7]([N+:4]([O-:6])=[O:5])[CH:8]=1)(=[O:17])[C:15]([CH3:20])([CH3:19])[CH3:14]To 300 mL of CH2Cl2 was added 3-nitrophenol (structure 64 of Scheme XVII, where R1=H, Y=O) (15 g, 0.11 mol), pyridine (20 mL) and DMAP (10 mg). To this cooled solution (0° C.) was slowly added trimethylacetyl chloride (18 mL, 146 mmol, 1.4 equivuiv). The solution was allowed to warm to rt and stirred for 3 h. To the amber colored solution was added sat'd NH4Cl (300 mL). The organic layer was washed with 1N HCl (2×150 mL), 10% CuSO4. 5 H2O (2×100 mL), and brine (2×100 mL). The extract was dried (Na2SO4) and concentrated in vacuo to give 22.5 g (94%) of O-pivaloyl-3-nitrophenol as a white solid. Data for O-pivaloyl-3-nitrophenol: Rf 0.55 (silica gel, hexanes/EtOAc, 3:1); 1H NMR (400 MHz, CDCl3) 8.11 (dd, J=4.2, 1.3, 1H), 7.96 (t, J=2.2, 1H), 7.56 (dd, J=8.4, 8.2, 1H), 7.42 (dd, J=6.5, 1.3, 1H), 1.35 (s, 9H).
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