Enolates ethyl

Allylic isomerization of carbon-heteroatom double bonds can be accompanied by the 1,3-shift of an atom or a substituent. An enol-kctone isomerization takes place with cnol ethers 1 to give the acid fluorides 2 when heated in the presence of a catalytic amount of triethylaminc,1,2 in the presence of dimethylformamidc or hexamethylphosphoric triamidc.3 or with triethyl phosphite.4 The authors propose that the enolate (CF3)2C = CF —O- is formed in the first step.2,5 This enolate can attack ether 1 in an SN2 reaction to give product 2 and regenerate the enolate. Ethyl ether 1 b requires more severe conditions than the corresponding methyl derivative la, presumably due to steric hindrance.2,5... 

Ethyl benzoate cannot undergo the Claisen condensation, because it has no protons on its a-carbon atom and so cannot form an enolate. Ethyl pentanoate and ethyl phenylacetate can undergo the Claisen condensation. 

P-Cyclopentylpropionic acid Testosterone 3-enol-ethyl ether Acetic anhydride Hydrogen chloride... 

Fig. 2 Unit-slope relation between the logarithms of rate constants for hydronium-catalysis of enol ketonisation (fcket0) and enol ethyl ether hydrolysis (fchydro) n the series of cycloalkanone (C H2 20) derivatives (Dubois et al., 1981)...

Mesembrine enol ethyl ether (IV) C19H27NO3 88.5-87 + 102.4° (C2H5OH) 10 ... 

Two pieces of evidence may be cited to support the theory that car-banions and not enols are involved in carbonyl condensation and alkylation reactions. First, the ultraviolet absorption spectrum of sodio-acetoacetic ester is very different from that of the enol ethyl ether... 

This conjugated ketone is prepared from cyclohexane-1,3-dione (1) via the enol ethyl ether (2), which is prepared by azeotropic distillation of a solution of (1)... 

When dichlorophenylborane in the presence of diisopropylethylamine is used to enolize ethyl ketones (see Scheme 9), excellent syn diastereoselectivity (>94 6) is observed (Scheme 19). Similar syn selectivity ranging from 90 to 99% depending on the aldehyde employed is recorded by Chow and Seebach when trichloroborane is used. 

The reaction between (2-oxoalkyl)phosphonic diesters and triethyl orthoformate in the presence of ironflll) chloride yields the enol ethyl ethers", while reactions with amines afford enamines. When heated with P4O10, enols may undergo dehydration, as in the reaction with diphenacylphosphinic acid in hot toluene, which gives the 1,4-oxaphospho-rin333". ... 

Kawase and co-workers also examined aminomalonate as a nucleophile with munchnones. In this reaction, initial attack at C-5 is followed by enolate cyclization onto the trifluoroacetyl group, leading to pyrrolidin-2-ones 100 (Fig. 4.34). The less enolic ethyl glycinate and iV-methylglycinate failed to react. 

Two procedures called the acetoacetic ester synthesis and the malonic ester synthesis take advantage of the properties of p-dicarbonyl compounds and are standard methods for making carbon-carbon bonds. Both begin with alkylation of the enolate. Ethyl esters are normally used, with sodium ethoxide as the base. 

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