Sodium ethoxide, as base

Using sodium ethoxide as base, the reaction does not proceed. This can be ascribed to the nature of the P-ketoester product, which contains no protons sandwiched between two carbonyls and, therefore, no protons that are sufficiently acidic for the hnal equilibrium-disturbing step. The reaction can be made to proceed, however, and the solution is simple use a stronger base. In this way, the base used is sufficiently powerful to remove a less acidic proton from the product, removing it from the reaction mixture and... 

These two diastereoisomeric cyclohexyl chlorides derived from menthol react very differently under the same conditions with sodium ethoxide as base. Both eliminate HC1 but diastereoisomer A reacts rapidly to give a mixture of products, while diastereoisomer B (which differs only in the configuration of the carbon atom bearing chlorine) gives a single alkene product but very much more slowly. We can safely exclude El as a mechanism because the same cation would be formed from both diastereoisomers, and this would mean the ratio of products (though not necssarily the rate) would be the same for both. 

S°C. By contrast, the formylation of ketone enolates with ethyl formate is usually carried out using sodium hydride or sodium ethoxide as base and generally requires 12 to 48 hr at room temperature for complete reaction. 

Recently, the bis(methylthio)methylene imine of pseudoephedrine glycinamide was shown to undergo diastereoselective alkylation at 23 °C with lithium terf-butoxide or sodium ethoxide as base and various alkyl halides as electrophiles (eq 21 ). This procedure was used to prepare enantiomerically enriched a-amino acids. 

Acylation of ketones. Noting that on alkylation of malononitrile in ethanol or benzene with sodium ethoxide as base the yield is only 70% and formation of imide esters is an important side reaction, Bloomfleld was led to try the non-nucleophilic base sodium hydride in dimethyl sulfoxide, a relatively non-nucleophilic solvent capable of dissolving intermediate salts. With this combination he obtained dimethyl-malononitrile in 60% yield. He then studied the acylation of the ketone (1) with the... 

The sleric cmiisc ol ihe reaclion of Ihe Willigrciincnl (-) with propionulUehydc lo give /3-ethylstyiene (3) is highly sensitive to the environmenlal conditions. When the reaction was carried out in DM F as solvent and sodium ethoxide as base and with... 

Some examples of alkylation reactions involving relatively acidic carbon acids are shown in Scheme 1.3. Entries 1 to 4 are typical examples using sodium ethoxide as the base. Entry 5 is similar, but employs sodium hydride as the base. The synthesis of diethyl cyclobutanedicarboxylate in Entry 6 illustrates ring formation by intramolecular alkylation reactions. Additional examples of intramolecular alkylation are considered in Section 1.2.5. Note also the stereoselectivity in Entry 7, where the existing branched substituent leads to a trans orientation of the methyl group. 

Thiopental Thiopental, 5-ethyl-5-(l-methylbutyl)2-thiobarbituric acid (1.2.10), is synthesized by the alkylation of ethyhnalonic ester with 2-bromopentane in the presence of sodium ethoxide. The product ethyl-(l-methylbutyl)malonic ester (1.2.9) undergoes hete-rocyclization with thiourea, using sodium ethoxide as a base [16,17]. 

The preparatively useful and simple N-alkylation procedure that utilizes a combination of carboxylic acid and sodium borohydride has been applied to carbazole giving an efficient 9-ethylation. Also of preparative importance is the use of thallous ethoxide as base in dimethylformamide-ether 9-methyl-, 9-ethyl-, n-propyl-, n-butyl-, benzyl-, and n-allylcarbazoles were efficiently produced, as well as 9,9 -dicarbazolylalkanes using C3, C4, and Cg dihalides. 2-Acetyl- and 2-vinylcarbazole were also efficiently 9-ethylated by this route. Another more recent approach to N-alkylation of carbazole utilizes potassium terf-butoxide in the presence of a catalytic quantity of 18-crown-6 9-methylcarbazole was prepared in high yield. ... 

The concentration of acidic groups can be determined by neutralization with a base, using solutions of sodium bicarbonate, sodium carbonate, sodium hydroxide or sodium ethoxide as titrants. Only those acidic groups which are much more strongly dissociated than the conjugate acids of the bases are completely neutralized. Thus, the differences in the amount of base required may be used to characterize the acidity of surface groups. Boehm (12) identified four different type of surface groups by this technique. 

In fact, even with an ester that gives an acceptable yield of the condensation product with sodium ethoxide as the base, a better yield is often obtained when a stronger base is employed. 

This protocol is representative of the Michaelis-Becker reaction in its simplest form, using sodium ethoxide as the base. It gives triethyl 3-phosphonopropionate 26 in better yield than the corresponding Michaelis-Arbuzov reaction (circa 60%), which suffers side reactions (substrates with -electron withdrawing groups are susceptible to dehydrohalogenation during the Michaelis-Arbuzov reaction).65... 

A more ingenious route involves the dehydrobromination of ester 1 in a benzene solution containing a catalytic amount of ethanol and using sodium hydride as base. The ethoxide ion, being a stronger base in benzene than in ethanol, deprotonates the substrate and is converted to ethanol. As a result much less ethoxide is available for addition to the triple bond, thus affording the ethyl phenylpropiolate and the ethyl P-ethoxycinnamate in ca. 56% and 27% yield, respectively . 

Initial studies of solvent effects, on the reactions of triarylarsonium benzoylylides with p-nitrobenzaldehyde in N, A-dimethylformamide, dimethyl sulphoxide or methanol, indicated little solvent effect in these cases" ", but later studies of the more finely balanced reactions of semi-stabilized ylides have provided examples of strong influences due to the effect of different base and solvent when the ylide is generated in the presence of a carbonyl compound ". Thus, when benzyltriphenylarsonium bromide or p-chloroben-zyltriphenylarsonium bromide were treated with sodium hydride in benzene in the presence of a variety of p-substituted benzaldehydes the products were alkenes, but if sodium ethoxide in ethanol was used the isolated products were epoxides ". Likewise, when triphenylarsonium benzylylide was generated by phenyllithium in the presence of either benzaldehyde or acetaldehyde, the preponderant product was the epoxide whereas use of sodium amide as base provided mostly the alkene . Similar results were obtained when an allyltriphenylarsonium salt was deprotonated using different hexamethyldisilaz-... 

Stobbe condensations. W. S. Johnson and Daub, having found potassium f-butoxide superior to sodium ethoxide as a base for carrying out the Stobbe condensation, found an even better base in sodium hydride. When a mixture of benzo-phenone, diethyl succinate, and sodium hydride was stirred at room temperature,... 

Reaction of the same starting material 15-2 with ethyl formate and sodium ethoxide, as in the case of the desalkyl series, proceeds to form the 2-formyl derivative 17-1 (Scheme 5.17). Exhaustive catalytic hydrogenation then gives the 2a-methyl derivative dromostanolone (17-2). The initial product, as in the case of the desoxy series, consists of the 2)8-methyl derivative from approach of hydrogen from the open backside. Treatment with base epimerizes this to the favored 2a-methyl epimer 17-3 (dromostanolone), in which the newly introduced methyl group is equatorial. 

Compared to that of the Ruzicka protocol, the Claisen-Geuther ester condensation in this synthesis was optimized from 17% to 64% by replacement of sodium ethoxide with sodium or sodium amide. In addition, the cyclization to form the piperidinyl ring is carried out in a two-phase solvent system (H2O and ether) using sodium carbonate as base. ... 

Most of the hydroxylated pulvinic acids from Basidiomycetes were first synthesised (7i, 200, 607, 608, 609) using the classical methods of VoLHARD 687) and Asano (52). For unsymmetrically substituted pulvinic acids such as xerocomic acid (72) the procedure is shown in Scheme 12 202). The use of sodium hydride as base in the second condensation step is recommended ( ) in order to reduce contamination of the dinitrile (99) with symmetrical by-products which arise via retro-aldol processes when sodium ethoxide is used. This route has also been followed for the synthesis of " C-labelled compounds 514). 

Abstract. Crown ethers derived from tartaric acid present a number of interesting features as receptor frameworks and offer a possibility of enhanced metal cation binding due to favorable electrostatic interactions. The synthesis of polycarboxylate crown ethers from tartaric acid is achieved by simple Williamson ether synthesis using thallous ethoxide or sodium hydride as base. Stability constants for the complexation of alkali metal and alkaline earth cations were determined by potentiometric titration. Complexation is dominated by electrostatic interactions but cooperative coordination of the cation by both the crown ether and a carboxylate group is essential to complex stability. Complexes are stable to pH 3 and the ligands can be used as simultaneous proton and metal ion buffers. The low extractibility of the complexes was applied in a membrane transport system which is a formal model of primary active transport. 

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. 

In the case of a strong base, such as sodium ethoxide, as a homogeneous catalyst, the selectivity was as low as 1-7% during the whole course of the reaction due to further conversion of the product toward an undesired cycUzation product (entry 11) [17]. The cooperative activation by the surface acid and amine group, which is a weaker base compared to sodium ethoxide, realizes selective catalysis compared to when using only a strong base. 

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