ClC1C(NCCCC(NN[S:20]([C:23]2[S:27][C:26]([CH2:28][NH:29][C:30](=O)[C:31]3[CH:36]=CC([N+]([O-])=O)=CC=3)=[CH:25][CH:24]=2)(=[O:22])=[O:21])=O)=NC=C(C(F)(F)F)C=1.[Li][C:42]([CH3:45])(C)[CH3:43].CCCCC.C1C(=O)N([Cl:58])C(=O)C1>CCOCC.C1COCC1>[CH2:43]([N:29]([CH2:28][C:26]1[S:27][C:23]([S:20]([Cl:58])(=[O:21])=[O:22])=[CH:24][CH:25]=1)[CH2:30][CH:31]=[CH2:36])[CH:42]=[CH2:45]A solution of the allyl-protected thiophene 19a (6.2 g, 32.1 mmol) in Et2O was cooled to −70° C. by means of an acetone/dry ice bath. A solution of t-BuLi in pentane (21.38 ml, 1.5M, 32.1 mmol) was added over 2 min whereupon the internal temperature momentarily rose to −50° C. and the mixture turned orange. After 10 min., SO2 was bubbled for 2 min, which led to the immediate formation of a thick precipitate. The reaction was allowed to reach 0° C., and a suspension of NCS (4.63 g, 32.1 mmol) in THF (20 ml) was added, whereupon the slurry turned purple. After 45 min at r.t., the mixture was filtered over SiO2, eluting with EtOAc. Evaporation, dilution with EtOAc:hexane 1:5 and filtration over SiO2 gave 5.0 g (53%) of the title sulfonyl chloride 19b as a pale brown oil which was used without further purification.
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