Rearrangements involving chlorosulfonic

The 1,5-thiazocine 566 was oxidized to chlorosulfone 457 by treatment with A -chlorosuccinimide in CCI4 and ot-MCPBA. The Ramberg-Backlund rearrangement involved conversion of the a-chlorosulfone 567 into the azepine 569 under basic conditions through the formation of episulfone 568 followed by extrusion of S02. The reaction was conducted using different bases, such as KO/-Bu (66% yield), aqueous KOH (43% yield), and alumina-supported KOH (63% yield) (Scheme 113) <2000JOC8367>. 

The latter compound 173 also results from heating the 1,5- or 1,6-disulfonic acids with excess chlorosulfonic acid, a reaction involving rearrangement of the 1-chlorosulfonyl group. ... 

Acetophenone 217, by mixing the excess chlorosulfonic acid in the cold followed by heating the mixture at 110 C (1 hour), gave a disulfonyl chloride which was originally considered to be the 3,5-derivative. However, subsequent work by Suter and Weston in which acetophenone 217 was treated with the reagent (10 equivalents) in carbon tetrachloride at 0°C and heated at 110 C (45 minutes) showed that the product was the 2,disulfonic acid 218 (X = OH) the reaction probably involves initial sulfation of the enolic form of the ketone 217 which then rearranges to form the co-sulfonic acid 219 (Scheme 1). 

Ozonides react with catalytic quantities of chlorosulfonic acid (0.3 equivalents) in dichloromethane at 20 °C to yield 3,6-dialkyl-1,2,4,5-tetraoxans and/or 1,4-dialkyl-2,3,5,6,ll-pentaoxabicyclo[5.3.1]undecanes. The reaction of ozonides with chlorosulfonic acid has been extensively investigated by Miura and co-work-ers. The reaction pathways appear to vary with different substituents the proposed mechanism involves heterolytic fission of the carbon-oxygen bond of the peroxide bridge. For example, methylcyclopentene ozonide 472 reacted stereo-selectively with the reagent in dichloromethane to give initially compound 473 which subsequently rearranged to form the trans tetraoxan 474 (Equation 151). 

Camphor-3-sulfonic acid may also be obtained (73% yield) by treatment of camphor with sulfur trioxide-dioxan at —35 °C, followed by standing the reaction mixture at room temperature (4 hours) and neutralization with sodium hydroxide. This reaction and that with methyl chlorosulfonate probably proceed via the enolic form of the ketone. The formation of 8- and 10-camphorsulfonic acids is considered to involve Wagner and Nemetkin rearrangements of the carbocations formed in the acidic media. ... 

Chlorosulfonic acid catalyses several interesting rearrangements of ozonides, which probably involve heterolytic fusion of the carbon-oxygen bond of the peroxide bridge. For instance, methylcyclopentene ozonide, on treatment with chlorosulfonic acid (0.3 equivalents) in dichloromethane at RT, rearranged to form a trans tetraoxan (see Chapter 4, p 125). Stilbene ozonide with chlorosulfonic acid under similar conditions, also afforded the corresponding tetraoxan and this appears a fairly general reaction. 

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