Acetoacetate anion

The 2-vinyloxiranes undergo Pd-catalysed furan annelation with soft nucleophiles [36,37], The allenylpalladium 170 is generated from ethynyloxirane 169, and the attack of acetoacetate anion 153 at the central carbon of 170 forms 171. The oxygen... 

We could presumably make 57 from 67 (compound 44 in chapter 19) by reduction and elimination. Addition of, say, acetoacetate anion should give 63. 

This is a direct SN2 displacement of the bromide anion of ferf-butyl bromoacetate by a methyl acetoacetate anion. Lithium bromide (LiBr), the salt by-product, is not shown in the reaction below. 

The first reaction stage is undoubtedly SN2 nucleophilic displacement of chlorine by the ethyl acetoacetate anion. Chlorine bond to carbon is weaker than that of fluorine. The resulting ethyl 5-fluoropentan-2-one-3-carboxylate subsequently cyclizes by an SNi reaction, displacing this time the fluorine atom [73]. 

A pair of electrons on oxygen, nitrogen, or sulfur adjacent to an unsaturated system can be made available for reaction through that system 6. This can also happen when the heteroatom carries a negative charge 7 the alkylation of the acetoacetate anion on carbon is an analogous reaction in aliphatic chemistry. 

The resonance-stabilized acetoacetate anion is no longer reactive toward nucleophiles, and no further reaction occurs at room temperature. Elevated temperatures are required to make the cleavage reaction proceed. This complication doesn t occur with ethyl dimethylacetoacetate because it has no acidic hydrogens between its two carbonyl groups. 

The Tsuji-Trost reaction involves Pd-catalyzed allylation of stabilized enolates and related compounds, such as malonate and acetoacetate anions. Since most of the counterions have been alkali metals, such as Li and Na, this vast topic is mostly outside the scope of this... 

After conversion to 19 (70% yield) via Nef reaction and ketalization, selective modification of the terminal olefin by reaction with LAH-TiCl4, quenching with I2, and displacement of the resulting terminal halogen with ethyl acetoacetate anion afforded 20 in 48% overall yield. Deacetylation with sodium ethoxide followed by deketalization under acidic conditions produced an 88% yield of keto ester 21. Seco acid 6 was then obtained (in 29% yield from 18) after reduction of the ketone and ester hydrolysis. Clearly, the significance of this... 

O-Alkylation is most pronounced when the enolate is least solvated. When the potassium salt of ethyl acetoacetate is treated with ethyl sulfate in the polar aprotic solvent HMPA, the major product (83%) results from O-alkylation. In THF, where ion clustering occurs, all of the product is C-alkylated. In r-butyl alcohol, where the acetoacetate anion is hydrogen bonded by solvent, again only C-alkylation is observed. 

Six-membered ring heterocycles, for example N-2-pyridyl, N-6-methylpyridyl and N-4-pyridyl-2,6-dinitro-4-pyridones have been used with the ethyl acetoacetate anion in pyridine solution at 65-70 C during 5 hours for the synthesis of ethyl... 

The spontaneous enolization of acetoacetic acid (measured as bromination) is 60 times faster than that of ethyl acetoacetate and 10 to 10 times faster than that of levulinic acid but the acetoacetate anion is unreactive. Also the glycollate- and acetate-catalysed enolization of acetoacetic acid is 30 to 40 times faster than the analogously catalysed enolization of ethyl acetoacetate [103]. A mechanism as symbolized by 64, where B is a water molecule or an acetate or a glycollate ion seems reasonable [101]. Similar rate enhancements were found in the enolization (studied as bromination) of 65 and 66 [104]. 

Scheme 6.3 Alternative mechanisms for the activation of a tra i-P-nitrostyrene and acetoacetate anion with the Takemoto catalyst[8]...

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