Dibenzothiophene-2-sulfonyl chloride

The Friedel-Crafts cyclization of biphenyl-2-sulfonyl chloride to give dibenzothiophene sulfone has been described (55%) ° however, thermal cyclization in octachloronaphthalene at 250°, under nitrogen, is reported to yield dibenzothiophene itself rather than the sulfone (47%). Reaction of biphenyl compounds with oleum (H2SO4 + SO3) to yield derivatives of dibenzothiophene 5,5-dioxide is widely used for the preparation of dyestuff intermediates (Section VI, E, 2). A typical example is shown in Eq. (3), starting from o-tolidine. ... 

Benzo[6]thiophene 1,1-dioxides have been made by cyclization procedures (Section 3.15.3.1.7). Homologs of acetophenone cyclize on treatment with chlorosulfonic acid to give 2-substituted 3-chlorobenzo[6]thiophene 1,1-dioxides (equation 86). Similarly 1,1-diaryl-1-propenes in concentrated sulfuric acid gave 2-methyl-3-arylbenzo[6]thiophene 1,1-dioxides (65JOC2840). Friedel-Crafts cyclization of l,l-diphenylethylene-2-sulfonyl chloride gave 3-phenylbenzo[6]thiophene 1,1-dioxide (equation 87) (59JA2000). Treatment of various biphenyl derivatives with fuming sulfuric acid forms the dibenzothiophene 5,5-dioxides (Section 3.15.3.1.7). 

Poliak et al. claimed that the reaction of biphenyl 32 with excess chlorosulfonic acid (six equivalents) at 18 °C affords dibenzothiophene-5,5-dioxide-3,7-disulfonyl chloride 34, but more recent attempts to reproduce this result were unsuccessful and only the 4,4 -disulfonyl chloride 33 (80%) was isolated. However, the cyclized product 34 was obtained in good yield (72%) when biphenyl 32 was heated with a large excess of chlorosulfonic acid (20 equivalents) at 150 °C (4 hours) (Equation 11). The reaction presumably involves the formation of the intermediate biphenyl-2,4,4 -trisulfonyl chloride, 35 which subsequently cyclizes with loss of hydrogen chloride to give the dibenzothiophene dioxide 34. Further study of the action of chlorosulfonic acid on biphenyl 32 showed that the optimum yield of the 4-sulfonyl chloride (43%) was derived from treatment of 32 with the reagent (1.5 equivalents) in thionyl chloride as solvent at 0 °C (1 week). The best yield (89%) of the 4,4 -disulfonyl chloride 33 was also achieved by treatment of the hydrocarbon 32 with chlorosulfonic acid (three equivalents) in thionyl chloride at room temperature (1 week). 

Dibenzothiophene reacts with chlorosulfonic acid (1.1 equivalents) in thionyl chloride for 10 days at RT to yield the 2-sulfonyl chloride 144 62%. ... 

Dibenzothiophene-5,5"dioxide 147 reacts with chlorosulfonic acid (five equivalents) for 2 hours at 50 C to yield the 3-sulfonyl chloride 148 65% (Scheme 10). On the other hand, when the dioxide 147 was strongly heated with a large excess of the reagent (10 equivalents) at 140 °C for 4 hours, the reaction afforded the 3,7-disulfonyl chloride 149 70% (Scheme 10). ... 

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