Sodium triphenylmethide

The formation of ethyl acetoacetate is an example of a general reaction knowu as the acetoacetlc ester condensation in which an ester having hydrogen on the a-carbon atom condenses with a second molecule of the same ester or with another ester (which may or may not have hydrogen on the a-carbon atom) in the presence of a basic catalyst (sodium, sodium ethoxide, sodamide, sodium triphenylmethide) to form a p-keto-ester. The mechanism of the reaction may be illustrated by the condensation of ethyl acetate with another molecule of ethyl acetate by means of sodium ethoxide. ... 

Only esters containing two a-hydrogen atoms (ethyl acetate, propionate, n-butyrate, etc.) can be condensed with the aid of sodium alkoxides. For esters with one a-hydrogen atom, such as ethyl tsobutyrate, the more powerful base sodium triphenylmethide PhaC Na leads to condensation with the formation of ethyl a-tsobutyrylisobutyrate ... 

The acetoacetic ester condensation (involving the acylation of an ester by an ester) is a special case of a more general reaction term the Claisen condensation. The latter is the condensation between a carboxylic ester and an ester (or ketone or nitrile) containing an a-hydrogen atom in the presence of a base (sodium, sodium alkoxide, sodamide, sodium triphenylmethide, etc.). If R—H is the compound containing the a- or active hydrogen atom, the Claisen condensation may be written ... 

Chapter III. 1 Heptene (111,10) alkyl iodides (KI H3PO4 method) (111,38) alkyl fluorides (KF-ethylene glycol method) (111,41) keten (nichrome wire method) (111,90) ion exchange resin catalyst method for esters (111,102) acetamide (urea method) (111,107) ethyl a bromopropionate (111,126) acetoacetatic ester condensation using sodium triphenylmethide (111,151). 

If pure triphenylchloromethane and freshly prepared sodium amalgam are used, the yield of sodium triphenylmethide should be almost quantitative but is usually 0-15 mol per fitre (1). The reagent should be used as socn as possible after its preparation. 

Triphenylmethyl sodium and triphenylmethyl potassium conduct in liquid ammonia although they slowly react with that solvent.887 888 When the liquid ammonia is allowed to evaporate from a solution of triphenylmethyl sodium in ammonia, the residue is a colorless mixture of sodamide and triphenylmethane. The sodium-tin and sodium-germanium compounds analogous to sodium triphenylmethide are also strong electrolytes in liquid ammonia. Sodium acetylide in liquid ammonia is dissociated to about the same extent as sodium acetate in water.889... 

The success of the reaction with sodium triphenylmethide as a catalyst might have been due to the conversion of the keto ester into a sodio... 

Sodium p-toluenesulphinate, 821,826 Sodium p toluenesulphonate, 548, 550 Sodium triphenylmethide, 477,479 Solid carbon dioxide, see Dry Ice Solid solution, 32, 34 Solidus, 26, 33... 

The amide ions are powerful bases and may be used (i) to dehydrohalogenate halo-compounds to alkenes and alkynes, and (ii) to generate reactive anions from terminal acetylenes, and compounds having reactive a-hydrogens (e.g. carbonyl compounds, nitriles, 2-alkylpyridines, etc.) these anions may then be used in a variety of synthetic procedures, e.g. alkylations, reactions with carbonyl components, etc. A further use of the metal amides in liquid ammonia is the formation of other important bases such as sodium triphenylmethide (from sodamide and triphenylmethane). 

For esters with only one a-hydrogen, such as ethyl 2-methyl propanoate (ethyl isobutyrate), a more powerful base (e.g. sodium triphenylmethide, Ph3CeNa ) is required to affect the condensation reaction [the forced Claisen ester condensation, e.g. the synthesis of ethyl 2,2,4-trimethyl-3-oxopentanoate (ethyl iso-butyrylisobutyrate), Expt 5.176]. In this case the reaction sequence is completed in the step corresponding to (ii) above since the /1-keto ester (24) has no a-hydro-gen for step (iii), and the powerful base is required to force the equilibrium (i) to the right. 

Aliphatic esters have been condensed with benzaldehyde by means of sodium triphenylmethide. The reaction has been stopped at the aldol stage to give low yields (26-30%) of /3-hydroxy esters. ... 

If the acylating ester is capable of undergoing self-condensation in the presence of sodium ethoxide, sodium triphenylmethide is substituted for the latter. An example is the reaction of acetonitrile with ethyl -butyrate to give n-butyrylacetonitrile (52%). ... 

Dialkylation of malonic ester proceeds in most cases almost as readily as monoalkylation. Diethyl ethylmalonate is alkylated equally well by s-octyl and n-butyl halides. Di-n-propylmalonic ester is prepared in one step from malonic ester and n-propyl bromide. Methylmalonic ester is alkylated by /3-phenylethyl bromide, and even a-naphthyl-malonic ester may be further alkylated by n-alkyl iodides. Difficulty is encountered, however, in introducing two s alkyl groups into malonic ester. A 23% yield of diisopropylmalonic ester is obtained from iso-ptopylmalonic ester, sodium triphenylmethide, and isopropyl iodide. ... 

The acylation of the sodium enolates of esters (prepared by sodium triphenylmethide) with acyl chlorides gives the corresponding a,a-di-substituted /S-keto esters, RCOCR, CO,C,H,. The synthesis is direct, and the product is free from monoalkylation products usually encountered... 

Esters having two a-hydrogen atoms give poor yields of alkylated product partly because of their greater tendency for self-condensation to /3-keto esters (method 211). Ethyl isovalerate, however, has been ethylated in 33% yield by treatment with sodium triphenylmethide and ethyl benzenesulfonate. ... 

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