3-ketocarboxylic acid ester

Thermal degradation prior to ionization can cause decarbonylation or decarboxylation of the analyte. Decarbonylation, for example, is observed from a-ketocarboxylic acids and a-ketocarboxylic acid esters, whereas decarboxylation is typical behavior of P-oxocarboxylic acids such as malonic acid and its derivatives and di-, tri-, or polycarboxylic acids. 

Of the five-membered heterocyclic ring derivatives, 0,0-diethyl-0-(3-methylpyrazolyl-5) phosphorothioate (51), introduced under the name Pyrazo-thion , is an insecticide with strong systemic action. The development of this compound was a further important result of the research program carried out by the research workers of the Geigy Co. on the phosphorus esters of enolisable heterocyclic compounds obtained from j -ketocarboxylic acid esters (Gysin and Margot, 1952). 

In gas-phase reactions zeolites are superior to non-zeolitic molecular sieves, metal phosphates, and metal oxides. Over the mildly acidic [B]-MFI (Si/B = 24) the synthesis of phenylpyruvic acid methyl ester yields up to 94 % at 200 °C and WHSV = 3 h 95 % product yield could be achieved with the cesium-doped material (0.6 % w w) [8]. With these concepts a-ketocarboxylic acid esters can be prepared from readily available feedstocks whereas conventional methods require the use of costly and environmentally problematical Grignard reactions. 

Hydrazones from diazonium salts a-Ketocarboxylic acid ester phenylhydrazones from /5-ketocarboxylic acid esters s. 2, 462, 813... 

Ketocarboxylic acid esters from ketones H —>- COOR... 

J-Ketocarboxylic acid esters from carboxylic acid esters s. 3,638 COCHRCOOR ... 

Keto-y-dicarboxylic acid esters from fi-ketocarboxylic acid esters s. 4, 770 ... 

Dihydroxynaphthalene ring from jd-ketocarboxylic acid esters... 

Ketones from / -ketocarboxylic acid esters COOR —H... 

The advantages of the new process for a-ketocarboxylic acid ester under gas phase conditions are high yields, high service time of the catalyst, and a one-step reaction using easily available starting materials. In contrast, the known processes are very complicated, costly and environmentally hazardous via Grignard reactions of oxalic acids. 

Among many classes of organic compounds the best results were obtained with the following combination a dihydrojg -dicarboxylic acid as modifier and a fteto-ketocarboxylic acid ester (or Z>era-diketone) as substrate. 

---