[C:1]([O:4][C:5]1[CH:6]=[C:7]([S:15]([OH:18])(=O)=[O:16])[CH:8]=[CH:9][C:10]=1[O:11][C:12](=[O:14])[CH3:13])(=[O:3])[CH3:2].CN(C)C(=O)C.C(N(CC)CC)C.P(Cl)(Cl)([Cl:34])=O>S1(CCCC1)(=O)=O.C(#N)C>[C:1]([O:4][C:5]1[CH:6]=[C:7]([S:15]([Cl:34])(=[O:18])=[O:16])[CH:8]=[CH:9][C:10]=1[O:11][C:12](=[O:14])[CH3:13])(=[O:3])[CH3:2]
To a solution of the crude, 3,4-diacetoxy benzene sulphonic acid (0.83 g) in a mixture of sulpholane (1.5 ml) and acetonitrile (1.5 ml) was added at room temperature successively N,N-dimethylacetamide (75 μl), triethylamine (0.85 ml) and phosphorus oxychloride (1.1 ml). The reaction mixture was thereafter heated for 15 minutes at 70° C., cooled, poured onto water and extracted with CH2Cl2. The extract was dried over magnesium sulphate, concentrated and chromatographed on silica gel (50 g). Elution with CH2Cl2 gave 0.65 g (74%) of the title compound as a white solid. NMR in CDCl3 : 2.33(s,6H); 7.29(d,1H); 7.90(s,1H); 7.95(dd,1H).
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