Sodium ethox ide

Amino-2,6-dimethylpyrimidine has been prepared by heating the reaction product obtained from acetic anhydride and acetamidine 1 by treating 4-chloro-2,6-dimethylpyrimidine with ammonia 2 and by heating acetonitrile either with sodium ethox-ide in a sealed tube3 or with sodium.4 6... 

This is an example of a general reaction by which haloesters are condensed with ketones by means of sodium,2 sodium ethox-ide,3 4 or sodium amide.5 6 1... 

Claisen condensation org chem 1. Condensation, in the presence of sodium ethox-ide, of esters or of esters and ketones to form p-dicarbonyl compounds. 2. Condensation of arylaldehydes and acylphenones with esters or ketones In the presence of sodium ethoxide to yield unsaturated esters. Also known as Claisen reaction. klas-3n kand-on sa-shon ... 

According to a i ule foi-mulated in 1875 by the Russian chemist Alexander Zaitsev, base-induced elimination reactions generally give the more highly substituted (more stable) alkene product—that is, the alkene with more alkyl substituents on the double-bond carbons. In the following two cases, for example, Zaitsev s rule is clearly applicable. The more highly substituted alkene product predominates in both cases when sodium ethox-ide in ethanol is used as the base. 

Because carbonyl compounds are only weakly acidic, strong bases are needed for enolate ion formation. If an alkoxide ion, such as sodium ethox-ide, is used as base, deprotonation takes place only to the extent of about 0.1%, because acetone is a weaker acid than ethanol (p/fg = 16). If, however, a more powerful base such as sodium hydride (NaH) or lithium diiso-propylamide [LiN i-C.3H7)2] is used, a carbonyl compound can be completely converted into its enolate ion. 

Esters, hkc aldehydes and ketones, are weakly acidic. When an ester with an reversible condensation reaction occurs to yield a /3-keto ester. For example, ethyl acetate yields ethyl acetoacetate on treatment with base. This reaction between two ester molecules is known as the Claisen condensation reaction. (We ll use ethyl esters for consistency, but other esters will also work.)... 

It is extraordinary that l,3-bis(dimethylaraino)vinylcarbene 324 obtained from vinylimmonium salts, containing an acceptor group, and sodium ethox-ide, adds to benzaldehyde with the formation of 2-phenyl-3-dimethylamino-furan 325 (78AG810). 

For these reactions, a large variety of base-solvent systems have been used, including sodium hydride in 1,2-dimethoxyethane or dimethylformamide, aqueous sodium hydroxide, butyl-lithium or phenyllithium in hexanes, potassium hydride in tetrahydrofuran, and sodium ethox-ide in ethanol. 

PROBLEM 23.4 Reaction of 1,2,3-tribromo-5-nitrobenzene with sodium ethox-ide in ethanol gave a single product, CgH7Br2N03, in quantitative yield. Suggest a reasonable structure for this compound. 

Polymer-bound 5-(2-bromoacetyl)pyrroles were converted into benzofurylpyrrolylketones through the addition of o-hydroxybenzaldehydes under basic conditions. Several bases were tested for this purpose, for example potassium tert-butoxide, BEMP (2-tert-bu-tylimino-2-diethylamino-l,3-dimethyl-perhydro-l,3,2-diazaphosphorine), sodium ethox-ide, and DBU.The best results were obtained with BEMP in NMP at 60°C (Fig. 6.18), the products being cleaved from the resin with 20% TFA/CH2C12. 

For an ester with two hydrogens on the a-carbon atom, the accepted mechanism, using sodium ethox-ide as catalyst, is shown in Scheme 2. With bases such as sodium ethoxide, with pA a 18, each of the... 

The preparation of 2-amino-substituted 5-ethoxypyrido[4,3-d]pyrimidines with sodium ethox-ide in ethanol 532 or of 2-alkyl(aryl)-6-benzyl-4-butoxy-5,6,7,8-tetraliydropyrido[4.3-chloro compounds prepared in situ has been developed. An example starting from the isolated chloropyrido[4,3-d]pyrimidine is the preparation of 5-ethoxy-2,7-diphenylpyrido[4,3-d]pyrimidine (6) from the 5-chloro compound 5.527... 

A synthesis of A Af-dialkyl-S-phenylpyridop -frlpyrazin-2-amine 4-oxides uses the cyclization of Af-(3-nitro-4-pyridyl)-Af, (V -dialkylphenylacetimidamides in refluxing ethanolic sodium ethox-ide.125... 

CH3COOR CH3COCH2COOR -I ROH The reaction is catalysed by sodium ethox-ide, the mechanism being similar to that of the aldol reaction, it is named after Ludwig Claisen (1851-1930). 

Both 4-amino and 4-dimethylamino substitution in 2-nitrobromo-benzenes greatly retards the reaction with piperidine as expected. The 4-NMe2 compound reacts 10 times faster than the 4-NHa compound even though the order of the +R effect is NMe2 > NH2 in electron release to aromatic rings. Moreover, in this case the unsubstituted compound reacts 10 times faster than the para-axmno compound. In contrast, the unactivated compounds, i.e. chlorobenzene and j -aminochlorobenzene, exhibit almost identical reaction rates in piperidine as also do bromobenzene and j -aminobromobenzene towards sodium methoxide at 150°c . However, aj ara-amino group lowers the reaction rates of o-fluoronitrobenzenes with sodium ethox-ide about one hundredfold. 

Reagents 1-naphthylmethylthiuronium chloride, 10% sodium ethox-ide (1 g of sodium metal is introduced with caution and cooling into 10 ml of abs. ethanol). 

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