Cl[C:2]([O:4][CH3:5])=[O:3].[C:6]([C:10]1[CH:15]=[C:14]([C:16]([CH3:19])([CH3:18])[CH3:17])[CH:13]=[CH:12][C:11]=1[OH:20])([CH3:9])([CH3:8])[CH3:7].CCN(CC)CC>CN(C1C=CN=CC=1)C.ClCCl>[CH3:5][O:4][C:2](=[O:3])[O:20][C:11]1[CH:12]=[CH:13][C:14]([C:16]([CH3:19])([CH3:18])[CH3:17])=[CH:15][C:10]=1[C:6]([CH3:9])([CH3:8])[CH3:7]Methyl chloroformate (58 mL, 750 mmol) was added dropwise to a solution of 2,4-di-tert-butyl-phenol (103.2 g, 500 mmol), Et3N (139 mL, 1000 mmol) and DMAP (3.05 g, 25 mmol) in dichloromethane (400 mL) cooled in an ice-water bath to 0° C. The mixture was allowed to warm to room temperature while stirring overnight, then filtered through silica gel (approx. 1 L) using 10% ethyl acetate-hexanes (˜4 L) as the eluent. The combined filtrates were concentrated to yield carbonic acid 2,4-di-tert-butyl-phenyl ester methyl ester as a yellow oil (132 g, quant.). 1H NMR (400 MHz, DMSO-d6) δ 7.35 (d, J=2.4 Hz, 1H), 7.29 (dd, J=8.5, 2.4 Hz, 1H), 7.06 (d, J=8.4 Hz, 1H), 3.85 (s, 3H), 1.30 (s, 9H), 1.29 (s, 9H).
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