Ketosulfones esters

The intermediate 3-sultone 508, obtained by addition of sulfur trioxide to l-ethoxy-l-trifluoromethyl-2,2-difluoroethylene, decomposes to a 3-ketosulfonate ester. A similar reaction is observed with 4-(l,2-dibromo-l,2,2-trifluoroethyl)-... 

All lation of Garbanions. Concentrated N a OH—hen syl triethyl amm onium chloride is the base/catalyst system normally used for this type of process (20). Classes of compounds alkylated in this way include phenylacetonitriles, ben2ylketones, simple aUphatic ketones, certain aldehydes, aryl sulfones, P-ketosulfones, P-ketoesters, malonic esters and nitriles, phenylacetic esters, indene, and fluorene (see Alkylation). 

Esters of chlorodifluoroacetic acids, like the esters of monofluoroacetic acid, can acylate anions (e.g., organometallic derivatives, enolates, lithiated sulfones). They lead to chlorodifluoromethylketones and to S-ketosulfones and jS-ketoesters which have the —CFj motif (Figure 2.16). ... 

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). 

Enhancement of the acceptor quality can be gained by switching from the ester group to a keto function. This has been realized by treating 258 with sodium or lithium salts of sulfones. In the resulting p-ketosulfones 259 the cyclopropane ring is... 

Enol phosphates of a-ketosulfones provide the key intermediate to alternate schemes leading to acetylenes. Acylation of phenyl sulfones with esters affords the ketone derivatives directly. Alternately, the ketones can be obtained by Moffat oxidation of the condensation products from aldehydes with sulfone anions. Conversion to the enol derivatives followed by treatment with Na/NH or Na(Hg) gives the acetylenes. 

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... 

Selective hydrolysis s. 19, 27 a-Ketosulfone hydrazones from a-azo- -ketosulfones Japp-Klingemann cleavage also ring opening s. 19, 28 Garbamyl disulfides from dithioformimidic acid esters s. 16,626... 

Gyclic -ketosulfones from sulfonylcarboxylic acid esters s. 11, 923... 

---