6-Keto esters, acylation olefinic

Olefin elimination and decarboxylation of ethyl t-butyl acylmalonates proceeds easily on treatment with toluenesulfonic acid to form /3-keto esters of the type RCOCH,CO,C,Hj. By this procedure, acyl acetates where R is ethyl (63%), cyclohexyl (65%), 2-furyl (70%), benzyl (46%), or propenyl (35%) have been prepared. The limiting factor in this excellent method is the availability of ethyl t-butyl malonate its synthesis has been described. ... 

Farina et al. used the chiral imine 7.1.3 to effect diastereoselective condensation with acetoxy acyl chloride to give preferentially the desired lactam in 74% yield and 84% diastereomeric excess. Subsequent deprotection of the silyl ether followed by mesylation and elimination afforded the olefin 7.1.4 which was ozonized. The resulting keto ester was easily hydrolyzed to give the unprotected lactam 7.1.5 in five steps (259). 

Acylation of a-lithio-a-phosphonylalkyl sulfides (440) with carboxylic acid esters was utilized as a facile route to a-alkylsulfenyl substituted p-ketophos-phonates (441). Keto-enol tautomerism of these new compounds in different solvents as well as regiochemistry of alkylation and acylation reactions and usefulness for HWE olefination reactions were studied (Scheme 104). ... 

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