Naphthyl tolyl sulfone

Similarly, 5-thiazole alkanoic acids and their salts are obtained from thioamides and /3-halo -y-keto acids (695). Thus thioarylamides condensed with 3-aroyl-3-bromopropionic acid (88) in isopropanolic solution in the presence of Na COs give first 4-hydroxy-2-aryl-A-2-thiazoline-5-acetic acid intermediates (89), which were dehydrated in toluene with catalytic amounts of p-toluene sulfonic acid to 2,4-diaryl-5-thiazole acetic acid (90) (Scheme 39) (657), with R = H or Me Ar = Ph, o-, m- or p-tolyl, o-, m-, or P-CIC6H4, 0-, m-, or p-MeOC(iH4, P-CF3C6H4, a-thienyl, a-naphthyl (657). 

The second synthesis of the enantiomer of this sulfone entails two transformations. First, (-)-a-naphthyl p-tolyl [ 0] sulfoxide 141 was converted into the corresponding [ 0] sulfoxide 141 by the method of Johnson (with inversion of configuration). Its oxidation with m-chloroperbenzoic acid afforded the chiral sulfone (+)-142 (Scheme 8). The latter procedure was also used for the preparation of chiral (-)-[ H2lbenzyl p-tolyl [ 0 0]sulfone (143) from (-)-[ H2] benzyl p-tolyl sulfoxide 37. 

CuHiiO-S p-Tolyl-oc-naphthyl-Bulfon 6 n 588. p-T< l- -naphtl l.sulfon (II011. "... 

The reactivity of the methylene hydrogen atoms towards the reagent apparently increased when the phenyl moiety of 117 was substituted by tolyl and naphthyl radicals which was suggested to be associated with their electronegativity. The proposed structure of the disulfonic acid 118 seems unlikely, since cyanoacetamide is inert towards chlorosulfonic acid while anilides are readily sulfonated by the reagent in the aryl ring (see Chapter 4, p 103). 

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