Benzenesulfonic acid 2-bromophenyl

Sultones are the internal esters of hydroxy sulfonic acids and sulfur analogs of lactones. The biological activities of sultones are concerned with toxicological, skin sensitization, and antiviral properties [13]. In 2009, Majumdar developed a Pd(PPh3)4-catalyzed intramolecular C-H arylation reaction of benzenesulfonic acid 2-bromophenyl esters to afford polycyclic sultones, which are generally synthesized by elimination of the corresponding hydroxyl sulfonic acid derivatives, in up to 90% yield (Scheme 3.3, path a) [14]. TBAB was found to be critical in this reaction, and no reaction occurred in the absence of this additive. An electrophilic palladation mechanism was proposed for this transformation. 

In 2009, Majumdar and coworkers developed a new efficient route for the synthesis of polycyclic sultones via ligand-free Pd-catalyzed intramolecular coupling reaction (Scheme 4.15) [22]. Using the optimized condition [Pd(PPh3)4/ TBAB/KOAc/DMF/100°C], benzenesulfonic acid 2-bromophenyl esters were successfully cyclized to afford the sultone in 90% yield. 

Scheme 4.15 Pd-catalyzed intramolecular coupling reaction of benzenesulfonic acid 2-bromophenyl esters.

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