Amides, alkali basicity

Base catalysis is most effective with alkali metals dispersed on solid supports or, in the homogeneous form, as aldoxides, amides, and so on. Small amounts of promoters form organoalkali comnpounds that really contribute the catalytic power. Basic ion exchange resins also are usebil. Base-catalyzed processes include isomerization and oligomerization of olefins, reactions of olefins with aromatics, and hydrogenation of polynuclear aromatics. 

Organometallic reagents and alkali metal amides can react via a cyclic transition state (Section II, B, 5) beginning with electrophilic attack at the most basic ring-nitrogen. As a result, sodamide (in dimethylaniline, 145°, 2 hr) yields the 4-amino derivatives (40% yield S)) methyl- or phenyl-magnesium iodides give the 4-adduct quantitatively.s ... 

Sulfonyl chlorides as well as esters and amides of sulfonic acids can be hydrolyzed to the corresponding acids. Sulfonyl chlorides can by hydrolyzed with water or with an alcohol in the absence of acid or base. Basic catalysis is also used, though of course the salt is the product obtained. Esters are readily hydrolyzed, many with water or dilute alkali. This is the same reaction as 10-4, and usually involves R —0 cleavage, except when R is aryl. However, in some cases retention of configuration... 

Thus amides are found to be only very weakly basic in water [pKa for ethanamide(acetamide) is =0-5], and if two C=0 groups are present the resultant imides, far from being basic, are often sufficiently acidic to form alkali metal salts, e.g. benzene-1,2-dicarboximide (phthalimide, 8) ... 

Diethyl A-alkylphosphonamides, obtained by the Atherton-Todd procedure (see procedure 5.1.13) are (V-alkylated under strongly basic two-phase conditions at reflux temperatures [56], The procedure is obviously limited to alkali-stable reagents and a better route involves the initial formation of the N-sodio salt of the phosphor-amidate, followed by alkylation under essentially neutral conditions (Table 5.28) [57],... 

Addition of a 2-alkynoic acid to alkali amide in liquid ammonia initially gives a solution of the alkali salt of the carboxylic acid. If an excess of alkali amide is present, the weakly basic salt is further deprotonated at a position next to the triple bond 183], This double deprotonation which may be compared with the formation of di-anions from 1,3-diketones and alkali amides [71], is essentially complete. The high kinetic stability of the alkynoic acid-dianion may be explained on the basis of resonance stabilization ... 

Reppe has shown that secondary amines of low basicity, such as carbazole, diphenylamine, indole, imidazole, and benzimidazole, and amides such as pyrrolidone react with acetylene in the presence of strong alkali to give vinyl derivatives [81, 83, 84a, b] (Eq. 30). As described by Reppe, these reactions are... 

An important class of alkali and alkaline earth metal amides are Mulvey s inverse crown complexes (also discussed in Chapter 2, dealing with sodium and potassium amides), in which cationic homo- or heterometallic macrocycles are hosts to anionic guest moieties.The term inverse crown indicates that the Lewis acidic/Lewis basic sites are reversed or exchanged in comparison to conventional crown ether complexes. Scheme 3.9 illustrates the range of recently published alkali and alkaline earth metal amide inverse crown complexes (for related Zn species see Chapter 7 on group 12 amides). 

Nitramines show no basic properties whatever — indeed, primary nitramines have distinct acidic properties and can form salts with alkalis. Conversely, nitr-amides may be more strongly acidic than carboxylic acids, as, for example, nitro-urethane, which is a stronger acid than formic acid. 

The rate is slower in basic aprotic amide solvents, and faster in acidic solvents such as / -cresol. In general, the imidization reaction has been shown to be catalyzed by acid (14,32,33). Thermal imidization of poly(amic acid)s is catalyzed by tertiary amines (34). High temperature solution polymerization in -cresol is often performed in the presence of high boiling tertiary amines such as quinoline as catalyst. Dialkylaminopyridines and other tertiary amines are effective catalysts in neutral solvents such as dichlorobenzene (35). Alkali metal and zinc salts of carboxylic acids (36) and salts of certain organophosphorus compounds (37) are also very efficient catalysts in one-step polycondensation of polyimides. 

Soluble glutenins Insoluble glutenins 15-35 Extractable in dilute acid or alkali (e.g., 0.05 N acetic acid) High-MW (100,000-3,000,000) complexes containing low-MW (40,000-10,000) subunits linked by disulfide bonds extra stabilization by hydrogen and hydrophobic interactions Rich in Glu, Pro, and hydrophobic amino acids, and low content of basic amino acids Glu and Asp in primarily amide form low net charge... 

If any base whose basicity exceeds the basicity of the caprolactam anion is applied, this kind of neutralization reaction results in formation of caprolactam salt, i. e. practically a metal salt of caprolactam. As far as the simultaneously formed component B-H does not interfere to the further catalytic action, especially if this compound is higly volatile and can be easily removed before having opportunity of such interference, the same result is obtained no matter what sort of base was used. Thus, extremely strong bases as alkali metals (7, 15, 18—22, 31, 42, 43, 46, 47, 49—51, 58, 71, 72, 100, 101), other strongly elektropositive metals (42), metal hydrides (12,31, 32, 51, 52) or metal amides react in a smooth way according the above scheme. The same result i. e. the formation of a caprolactam salt is obtained starting with relatively weak bases as alkali hydroxides (1, 5, 6, 10, 12, 13, 16—19, 28, 29, 33—35, 37—41,44, 45, 51, 54, 60, 64, 70—72, 78, 79, 100, 102) or alcoxides (9, 45), leading to an equilibrium... 

With respect to the base, it is obvious, that any impurity which can reduce the basicity of the alkali caprolactam or completely neutralize the amide anions [-C0—N—], i. e. any acid stronger than caprolactam, destroys completely the catalytic activity. 

Substituted aromatic carboxylic acid amides of the type ArCONHR and Ar-CONR2 are only slowly attacked by aqueous alkali and are characterised by hydrolysis under acidic conditions 70 per cent sulphuric acid (prepared by carefully adding 4 parts of acid to 3 parts of water) is the preferred reagent. Use the general procedure which has been outlined on p. 1229 characterise the acidic and basic components. 

Methyldecamine (174) was synthesized from pelletierine and the alkali-insoluble amide 170 by Hanaoka et al. (81). Decamine (18) was synthesized by Lantos et al. by the kinetically controlled condensation of pelletierine with biphenyl aldehyde (169) which afforded the cfs-quinolizidone (173) in 50% yield. Reduction of the carbonyl group with Henbest catalyst followed by alkaline hydrolysis produced the undesirable trans-fused quinolizidols as a major product. However, hydrogenation with platinium catalyst in an alkaline solution afforded the less stable cis-fused axial carbinol, which on cyclization followed by a mild basic hydrolysis yielded decamine (18). 

Is there a small cluster chemistry based on lanthanide amides Is alkali metal ate complexation just an annoying fact Is there a real potential for lanthanide amides in material sciences and catalysis The synthetic chemist is challenged by these questions and more, and hopefully the previous sections can deliver some basic tools for tackling these topics. 

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