C[Si](C)(C)[CH:3]1[S:8][CH2:7][CH2:6][CH2:5][S:4]1.C([Li])CCC.[OH:16][C:17]1[CH:30]=[CH:29][C:20]([C:21]([C:23]2[CH:28]=[CH:27][CH:26]=[CH:25][CH:24]=2)=O)=[CH:19][CH:18]=1.Cl>O1CCCC1.CCCCCC.O>[S:4]1[CH2:5][CH2:6][CH2:7][S:8][C:3]1=[C:21]([C:20]1[CH:19]=[CH:18][C:17]([OH:16])=[CH:30][CH:29]=1)[C:23]1[CH:24]=[CH:25][CH:26]=[CH:27][CH:28]=1
To a solution of 2-trimethylsilyl-1,3-dithiane (29.1 g) in dry tetrahydrofuran (600 ml) is added at -65° a 1.4M solution of n-butyllithium in hexane (108 ml). The reaction mixture is progressively warmed to 0° during 4 hours and cooled to -65°. A further 1.4M solution of n-butyllithium in hexane (108 ml) and a solution of 4-hydroxybenzophenone (30.0 g) in dry tetrahydrofuran (180 ml) are added, the temperature being maintained under -60°. The reaction mixture is progressively warmed to room temperature overnight. The suspension is slowly poured into water (2 l) and acidified to pH 2 with hydrochloric acid (32%). The compound is immediately extracted with ethyl acetate (4×500 ml). The combined organic solutions are washed with water (3×250 ml) and dried over magnesium sulphate. The solvent is evaporated in vacuo. The residue is washed with hexane (3×50 ml) and then recrystallized from carbon teytrachloride. The product is dried in vacuo to constant weight to give (1,3-dithian-2-ylidene)-(4-hydroxyphenyl)-phenylmethane, m.p. 135°-137°.
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