Sulfur halogen displacement

The principal focus of our examination of the experimental data in Tables IV through IX will be the dependence of the quantity log(ks/kH2o)r on the structures of both the sulfur nucleophile and the haloaliphatic substrate. Log(ks/kH2o)r (referred to here as the "substrate selectivity" for reaction r) is a measure of the selectivity of a particular substrate between each of the sulfur nucleophiles and H2O with respect to halogen displacement via substitution (if r SN) or dehydrohalogenation (if r E). The use of log(ks/kjj2o)r f°r this purpose serves two functions It "normalizes" sulfur nucleophile reactivity data to a common point of reference, and it gives an indication of the importance of each sulfur nucleophile in reactions with the substrate of interest, relative to the most abundant nucleophile in natural waters, H2O. 

Other approaches to Cr-mediated aromatic thiation have been studied [24], and quenching of lithiated arenetricarbonylchromium complexes by electrophilic sulfur has been compared to halogen displacement by nucleophilic sulfur. 

CENTRAL RING CONTAINING ONE HETEROATOM Reaction of 2-bromobenzoic acid (1) with chloroSulfonic acid proceeds to afford the sulfonyl chloride 2 treatment with dimethylamine leads to the corresponding sulfonamide (3). Condensation of bromoacid 3 with the anion from thiophenol in the presence of copper powder results in displacement of halogen by sulfur... 

One of the two classic schemes for constructing the thiazole ring involves the condensation of a thioamide or its equivalent with an a-haloketone. The reaction can be visualized as involving, as the first step, the displacement of halogen by sulfur from the enol form of the amide imine formation will then close the ring. Thus, reaction of bromoketone (99-2) obtained from the bromination of the corresponding keto-acid with thioamide (99-1) affords thiazole (99-3) in a single step. There is thus obtained the NSAID fentiazac [109]. 

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