Esterification Esters, acetoacetic

The patent describes the formation of complex metal chelates by treatment of the ketoester simultaneously with an alcohol and a metal to effect trans-esterification and chelate formation by distilling out the by-product ethanol [1], This process was being applied to produce the zinc chelate of 2-tris(bromomethyl)ethyl acetoacetate, and when 80% of the ethanol had been distilled out (and the internal temperature had increased considerably), a violent decomposition occurred [2], This presumably involved interaction of a bromine substituent with excess zinc to form a Grignard-type reagent, and subsequent exothermic reaction of this with one or more of the bromo or ester functions present. 

Polar yellow 5G is prepared by condensing p-chloro-m-sulfophenylhydrazine with acetoacetic ester, and coupling the resulting pyrazolone with diazotized p-aminophenol in acetic acid solution. The alkali sensitive dye which is formed is treated at 70°C. with p-toluenesulfonyl chloride, in the presence of soda and 1 mole of sodium hydroxide, to esterify the hydroxyl group. This esterification makes the dye insensitive to alkali and, at the same time, fast to milling on wool. 

The ester so obtained,uniijce most acetoacetic ester derlvatires,may be hydrolyzed to the free acid without decomposition. Their general behavior is like that of the 1,1 diacid,the same reactivity of the ring being characteristic of both the benzoyl and acetyl compounds. The ester when treated with cold hydro-bromic acid gives y-bromethylacetacetic esterif the acid is used,carbon dioxide is evolved andy -brom-propyl jcetone results ... 

Esterification of amino acids. The amino group of an amino acid can be protected as the enamine 1, formed by reaction with ethyl acetoacetate and a base in benzene/ DMSO. After alkylation the protective group is removed by addition of an acid, particularly TsOH, to provide amino acid ester salts (equation I). 

Two strategies have been developed for the preparation of esters of diazoacetic acid. If the alcohol is inexpensive, it is first converted (diketene) into the corresponding acetoacetate (120 equation 49). Diazo transfer with subsequent deacylation then yields the diazoacetate (121). If the alcohol is particularly valuable or sensitive, it may alternatively be esterified with a more direct precursor to diazoacetate. One reagent that has been used for this purpose is glyoxalic acid 2,4,6-triisopropylbenzenesulfonylhydrazone (TIPPS) (123 equation 50). Esterification of the alcohol (122) with (123), using dicyclohexylcarbo-diimide followed by addition of 4-dimethylaminopyridine, gives the diazoacetate (124). ... 

Total syntheses of this group also include the synthesis of 11-oxo-steroids described in the patent literature [1066] (Scheme 118). The starting material used was the cyanoester (413) formed by the condensation of acetoacetic and cyanoacetic esters. The successive addition of hydrogen cyanide and acrylonitrile, hydrolysis, decarboxylation, and esterification of the product led to the tetraester (414). Dieckmann condensation, hydrolysis, decarboxylation, and esterification gave the monocyclic... 

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