0-Keto phenyl sulfoxides

Among other electrophilic reagents ctq>able of twinging about the Pummerer rearrangement are halides of organic and inorganic acids. As these halides transform sulfoxides into a-chlorosulfides they complement the sulfide chlorination route to these compounds. Thionyl chloride reacts readily with sulfoxides and 3-keto sulfoxides methyl phenyl sulfoxide furnishes chloromethyl phenyl sulfide (equation 37). Benzoyl chloride and acetyl chloride behave similarly. d yanuric chloii is transformed into cyanuric acid by dimethyl sulfoxide, which in turn is transformed into methyl chloromethyl sulfide (equation 3g).54,S5... 

The a-chloro-a-sultinyl ketone 20 was prepared from methyl benzoate and chloromethyl phenyl sulfoxide 19 after in situ a-lithiation. Compound 20 is dimetallated by KH and f-BuLi to give the keto dianion 21, which is converted into a potassium/lithium ynolate 22 (equation 7). The resulting metal ynolates are converted into thioesters, carboxylic acids, amides and esters (Section V). 

In a like manner, vinyl sulfoxides and sulfones can serve as the equivalents of vinyl and alkenyl cations via a process involving a Michael addition followed by an elimination.43 For example, addition of the enolate of the P-keto ester (168 Scheme 24) to phenyl vinyl sulfoxide (169) furnished, in 50% yield. 

In the latter cases, the stereoselective formation of keto sulfoxides 153 and 154 has been observed instead of the expected dicarbonyl compounds 151 (as found for 3-methyl-2-phenyl-5,6-dihydro-1,4-oxathiin (116), Sch. 67), only in the presence of an electron withdrawing group at the double... 

Chlorosulfides are often used for vicinal functionalization of alkenes. Silyl enol ethers can react with a-chloromethyl phenyl sulfides (5) in the presence of ZnBr2 or TiCU to give the corresponding -keto sulfide, which could be easily transfonned into the a-methylene ketone via sulfide oxidation to sulfoxide, followed by pyrolytic elimination (Scheme 23). 

Isopropyl 2-iodoxybenzoate is a useful reagent for the clean, selective oxidation of organic sulfides to sulfoxides [1127]. This reaction proceeds without overoxidation to sulfones and is compatible with the presence of the hydroxy group, double bond, phenol ether, benzylic carbon and various substituted phenyl rings in the molecule of organic sulfide. Duschek and Kirsch have reported that isopropyl 2-iodoxybenzoate in the presence of trifiuoroacetic anhydride can be used for the a-hydroxylation of p-keto esters at room temperature in THF [1128]. 

Startg. -keto ester in dimethyl sulfoxide added at 25 under argon during 5 min. to a stirred mixture of benzaldehyde and zinc in dimethyl sulfoxide, and stirring continued 11 hrs. 5-hydroxy-4-methyl-5-phenyl-3-pentanone. Y 92%. F. e. s. T. Mukaiyama et al., Chem. Lett. 1976, 95. 

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