[CH3:1][N:2]1[CH2:7][CH2:6][S:5][CH2:4][C:3]1=[O:8].C([Li])CCC.CCCCCC.[C:20]([C:24]1[CH:29]=[C:28]([CH3:30])[CH:27]=[C:26]([C:31]([CH3:34])([CH3:33])[CH3:32])[C:25]=1[OH:35])([CH3:23])([CH3:22])[CH3:21]>O1CCCC1.[Ag]=O>[CH3:23][C:20]([C:24]1[CH:29]=[C:28]([CH2:30][CH:4]2[S:5][CH2:6][CH2:7][N:2]([CH3:1])[C:3]2=[O:8])[CH:27]=[C:26]([C:31]([CH3:34])([CH3:33])[CH3:32])[C:25]=1[OH:35])([CH3:21])[CH3:22]
4-methyl-3-thiomorpholinone (1.88 g, 14.3 mmol) dissolved in tetrahydrofuran (72 ml) was cooled to 0° C. and treated with 1.37M n-butyl lithium in hexane (20.9 ml, 28.7 mmol). After five minutes, the cold bath was removed. Ten minutes later a solution of 2,6-di-t-butyl-quinone methide, prepared by adding silver oxide (33.2 g, 143 mmol) to 2,6-di-t-butyl-4-methyl-phenol (BHT) (3.16 g, 14.3 mmol) in tetrahydrofuran (72 ml) stirring for 30 minutes and filtering, was added dropwise over 20 min. The reaction was stirred for three hours, quenched with 1N hydrochloric acid, and evaporated to an aqueous suspension. The crude product was extracted into ethyl acetate, dried over sodium sulfate and concentrated in vacuo. Chromatography on silica gel eluting with 8 L of a 0-50% ethyl acetate in hexane gradient yielded desired product (2.0 g, 40%):
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