Subject boron sulfides

Chlorosulfonyl benzoates were synthesized from 2-aryldimethyloxazolines 17 (Scheme 5). Sequential treatment with n-butyllithium and dipropyl disulfide afforded sulfides 18. The oxazolines 18 were then hydrolyzed to the benzoic acids 19 under acidic conditions. Fisher esterification gave the esters 20, which were oxidized to the corresponding sulfonyl chlorides 21 using chlorine and aqueous acetic acid. When methoxy-substituted benzoic acids (19, X = OMe) were employed, further manipulations were performed prior to oxidation. For example, phenol (22) was prepared by demethylation with boron tribromide, subjected to esterification, and then alkylated by a variety of electrophiles to provide 23. As before, 23 was oxidized using chlorine and aqueous acetic acid. 

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