Dibenzothiophene-5,5-dioxide-3-sulfonyl

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). 

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). 

It has been observed that sulfones do not decompose photochemically in the absence of sensitizer on irradiation above 3200 A so that the excited state is likely to be a triplet. It is possible that intersystem crossing to the vibrationally excited ground state occurs prior to bond breakage, but this is by no means certain . Occasionally rearrangement is observed in the decomposition of sulfones e.g., pyrolysis of dibenzothiophene-5,5-dioxide gives dibenzofuran instead of the de-sulfonylation product, biphenylene, viz. 

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). ... 

The electron-withdrawing property of the sulfonyl moiety in dibenzothiophene-5,5-dioxide 147 is reflected in the more drastic conditions required for the chlorosulfonation of this substrate as compared with those needed for diben-zothiophene 143. It also accounts for the observed orientation of sulfonation in the 3- and 3,7-positions, since these are both meta to the deactivating sulfonyl group and pam to the activating bridge bond. The pattern to sulfonation shoAvn by the dioxide 147 is similar to that of biphenyl (see Chapter 4, p 42). 

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