Esters, 1,6-keto synthesis, Reformatsky reaction

In the follow-up detailed report, Hudlicky s group (53) also described the synthesis of homoharringtonine from the unsaturated keto acid 151 (Scheme 23). Acid 151 was treated with formic acid in the presence of perchloric acid to provide the intermediate formylated derivative 163, which, on treatment with aqueous sodium hydroxide, produced hydroxy acid 164. Esterification of 164 with cephalotaxine yielded the cephalotaxyl ester 165, which underwent the Reformatsky reaction with methyl bro-... 

Reformatsky reactions. A practical synthesis of P-hydroxy-a,a-difluoroalkanoic esters involves halodifluoroacetic esters and induction by Smij. a-Bromoalkanoic esters undergo self-condensation, and if they are quenched by carbonyl compounds, 5-hydroxy-p-keto esters are formed as products. ... 

Palladium is a useful catalyst in several reactions which lead to keto-esters. p-Keto-esters react with allylic carbonates, with catalysis by palladium, in a decarboxylative allylation reaction. y-Keto-esters are prepared, in reasonable yield, by the palladium-catalysed regioselective oxidation of Py-unsaturated esters. y-Keto-esters are obtained in good yield by the palladium-catalysed Reformatsky reaction of ethyl bromoacetate and acid chlorides. Derivatives of y-ketopimelic acid are formed by the rhodium-carbonyl-catalysed reaction of derivatives of acrylic acid with carbon monoxide. A mild method for the conversion of propiolic esters into P-keto-esters via thiol addition has been reported (Scheme 63) it has been used in a formal synthesis of ( )-thienamycin. 

---