Enolate anions, esters, reaction with acid chlorides

Aldehydes may be prepared from the lower homolog or a ketone or ester by reaction with the anion of formaldehyde mono- or dithioacetal. The j6-hydroxythioacetal may be reduced with elimination of a hydroxyl group and phenylthiolate. The resulting enol ether or thioenol ether can be transformed into an aldehyde on acid hydrolysis or reaction with mercuric chloride [82],... 

Synthesis of trifluoromethylated compounds 152 has been achieved via ester-enolate [2,3]-Wittig and [3,3]-lreland-Claisen rearrangements. Perfluorocyclo-butane phosphonium ylides, e.g. 153, have been used as a masked fluoride anion source in their reactions with alcohols and carboxylic acids which lead to alkyl-and acyl-fluorides. Ylides 153 are also reported to cleave Si-C and Si-O bonds, cause dimerisation of fluoro-olefins, and also react with acid chlorides or other activated aromatic compounds under halogen exchange. ... 

A new synthesis of aldehydes with 2-methyl-2-thiazoline has the advantage of releasing the aldehydes from the thiazolidine intermediate under neutral conditions . Acetylene derivatives can be obtained from aldehydes via dibromomethylene compounds Novel reactions of alkynes with cationoid electrophiles have been published. -Diketones and 2-ketoalkoximes can be obtained by this reaction from acid chlorides and aliphatic nitro compounds respectively Addition of aldehydes to activated carbon-carbon double bonds occurs smoothly in the presence of cyanide ions as catalysts . Poly- -carbonyl compounds have been prepared by condensation of two anions, whereby the enolate salt of a y8-keto ester condenses as an electrophilic anion with strong nucleophiles such as the dianion of benzoylacetone. ... 

The substrate arachidonic aeid, whieh often leads to formation of inflammatory prostaglandins, is stored in tissues as one of a number of phospholipids these compounds, as the name indicates, comprise complex phosphate-containing esters. The antiinflammatory corticosteroids inhibit the action of the enzyme, phospholipase A2, that frees arachidonic acid. The many undesired effects of those steroids has led to the search for non-steroidal inhibitors of that enzyme. A highly substituted indole derivative has shown good activity as a phospholipase A2 inhibitor. Alkylation of the anion from treatment of indole (32) with benzyl chloride affords the corresponding A-benzylated derivative (33). The methyl ether at the 4 position is then cleaved by means of boron tribromide to yield 34. Alkylation of the enolate from reaction of the phenol with sodium hydride with tert-butylbromoacetate affords the corresponding... 

Disconnection (1) means that we are looking for a reaction which is the acylation of an enolate anion (2). This is possible with esters (X = OR) or acid chlorides (X = Cl), The perfumery compound (5) (which has a fragrant balsamic odour of great power and tenacity ) can be disconnected to the enolate of a ketone and an ester. 

Anions obtained from acetoacetic esters undergo acylation when they are treated with acyl chlorides or acid anhydrides. Because both of these acylating agents react with alcohols, acylation reactions cannot be carried out in ethanol and must be carried out in aptotic solvents such as DMF or DMSO (Section 6.13C). (If the reaction were to be carried out in ethanol, using sodium ethoxide, for example, then the acyl chloride would be rapidly converted to an ethyl ester and the ethoxide ion would be neutralized.) Sodium hydride can be used to generate the enolate ion in an aptotic solvent ... 

A last example shows the reaction of a vinyl chloride such as 3.30 with ethylamine (see reaction 7). Addition of the amine generated the usual enolate anion intermediate, which displaced the P-chlorine to give a new conjugated ester. In this case, the product was ethyl 3-(N,N-diethylamino)but-2-enoate (3.57).23 The yield was relatively poor, but this example illustrates that conjugate addition of amines can lead to either the normal saturated product or, as in this case, an unsaturated amino acid. 

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