Carboxylic ketosulfones

The reaction of 6-methylpyridine-3-carboxylic acid methyl ester with N,0-dimethylhydroxylamine and isopropyl-magnesium chloride in toluene gives the N-methoxyamide derivative (x), which is reduced with diisobutyl aluminium hydride (DIBAL) to afford 6-methylpyridine-3-carbaldehyde (xi). The reaction of the aldehyde (xi) with a phosphite provides the diphenyl phosphonate derivative, which is condensed with 4-(methylsulfonyl)benzaldehyde in the presence of potassium fe/f-butoxide in HF to yield the enimine (xii). Finally, this compound is hydrolyzed with HCI to yield the ketosulfone (ix). 

Alternatively the oxidation of 4 -(methylsulfonyl) acetophenone with S8 and morpholine produces the 2-(4-(methylsulfonyl)phenyl)acetic acid ethyl ester (xiv), which is condensed with 2-methylpyridine-3-carboxylic acid methyl ester by means of terf-butyl magnesium chloride in hot tetrahydrofurane to give the ketosulfone (ix). 

Applications of the chiral rhodium (II) carboxylates to the cycHzation of a-di-azo-p-ketosulfones, Eq. (35), have shown that while they are catalytically active at or below room temperature, they provide only low enantiomeric excesses [6]. 

New photochemical methods for the synthesis of esters and ketones have been also established. For instance, the visible-light mediated photoredox reaction of a-brominated carboxylates with enamines allowed to obtain y-ketoesters in good yields, under very mild conditions. Symmetrical and unsymmetrical 1,4-diketones could be synthesised from p-ketosulfones by visible light-induced C-S bond activation using... 

Potassium tert-butoxide/dimethylsulfoxide j -Ketosulfones from carboxylic acid esters... 

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