Hydration of nitriles

The hydration of nitriles has been used to synthesize amides, for example, by treating stearonittile in ether with dry hydrochloric acid followed by the addition of water to give a 73—94% yield of stearamide or its hydrochloride (25). The long reaction time at 0°C and the use of ether make this route of tittle commercial value. 

Schemes 6-19 Catalytic cycle of hydration of nitriles catalyzed by RuH2(PPh3)4...

We also found that iridium hydrido(hydroxo) complexes like [ lrH(diphos-phine) 2( x-OH)2( x-Cl)]Cl (43) and the precursor diphosphine complexes 42 can also catalyze the hydration of nitriles. In the presence of catalyhc amounts of these complexes, heating acetonitrile and benzonitrile with excess water at 120°C gave the corresponding amides [47, 50]. 

Kostic et al. recently reported the use of various palladium(II) aqua complexes as catalysts for the hydration of nitriles.456 crossrefil. 34 Reactivity of coordination These complexes, some of which are shown in Figure 36, also catalyze hydrolytic cleavage of peptides, decomposition of urea to carbon dioxide and ammonia, and alcoholysis of urea to ammonia and various carbamate esters.420-424, 427,429,456,457 Qggj-jy palladium(II) aqua complexes are versatile catalysts for hydrolytic reactions. Their catalytic properties arise from the presence of labile water or other solvent ligands which can be displaced by a substrate. In many cases the coordinated substrate becomes activated toward nucleophilic additions of water/hydroxide or alcohols. New palladium(II) complexes cis-[Pd(dtod)Cl2] and c - Pd(dtod)(sol)2]2+ contain the bidentate ligand 3,6-dithiaoctane-l,8-diol (dtod) and unidentate ligands, chloride anions, or the solvent (sol) molecules. The latter complex is an efficient catalyst for the hydration and methanolysis of nitriles, reactions shown in Equation (3) 435... 

Nitrile hydratase (NHase) catalyzes the hydration of nitriles to amides (Figure 1.11) and has been used for production of acrylamide and nicotinamide at large scale. NHases are roughly... 

In addition, they are formed in the partial hydration of nitriles by the action of strong mineral acids. An example of this reaction is given on p. 140. 

Partial hydration of nitriles to form amides is accomplished under mildly basic conditions, when catalysed by the addition of manganese pentacarbonyl bromide and benzyltriethylammonium chloride [30]. Yields are considerably reduced in the absence of the ammonium salt. 

Hydration of nitriles providing carboxamides is usually carried out m strongly basic or acidic aqueous media - these reactions require rather bars conditions and suffer from incomplete selectivity to the desired amide product. A few papers in the literature deal with the possibihty of transition metal catalysis of this reaction [28-30]. According to a recent report [30], acetonitrile can be hydrated into acetamide with water-soluble rhodium(I) complexes (such as the one obtained from [ RhCl(COD) 2] and TPPTS) under reasonably mild conditions with unprecedently high rate... 

Smejkal, T. and Breit, B. (2007) Self-assembled bidentate ligands for ruthenium-catalyzed hydration of nitriles. Organometallics, 26, 2461-2464. 

A variety of methods exist for the hydration of nitriles to amides or to acids (ref. 8). While acidic and basic catalysts have long been employed, the importance of catalytic hydration, especially under neutral conditions, is... 

Hydration of nitriles. The hydration of nitriles to amides is commonly carried out under acid or basic catalysis. The reaction can be carried under neutral conditions by catalysis with a black powder consisting essentially of Cu(0), obtained by reduction of CuS04 with NaBH4 in aqueous NaOH. The method is applicable even to sparingly water-soluble nitriles, and yields range from 50-95% (crude). ... 

H. Yamada and T. Nagasawa, Production of useful amides by enzymatic hydration of nitriles, Ann. N. Y. Acad. Sci. (Enzyme Engineering 10) 1990, 613, 142-154. 

Particularly well-studied examples of the hydration of nitriles are seen with the chelating ligands 2-cyano-1,10-phenanthroline (4.1) or 2-cyano-8-hydroxyquinoline (4.2). The products of the reactions are the appropriate amides, and the rate of hydration is enhanced by up to ten million times on co-ordination to nickel(n), copper(n) or cobalt(m). 

Hydrogen peroxide-Dimethyl sulfoxide. Hydration of nitriles. This conversioi... 

Hydration of nitriles. This conversion can be effected conveniently in 65-99% yield by reaction of nitriles with H202 (30%) in DMSO in the presence of K2C03 as catalyst. The reaction is complete in 1-30 minutes and ester or urethane bonds are not affected. 

Interestingly, catalytic turnover can be achieved for the hydration of nitriles with the Co(iii) complex (13). Hence, fundamental information gained from studying intramolecular model systems (8-11) that do not give catalytic turnover can be applied to obtain true catalysts. Lewis add activation and nucleophile activation can also be combined using mononudear Co(iii) [56], Cu(ii) [51] or Zn(n) [32] complexes to hydrolyze unactivated esters with catalytic turnover. 

Another numerical experiment involved a model active site of Fe-dependent nitrile-hydratase (Nhase), a non-heme Fem enzyme that catalyzes the hydration of nitriles to amides. The mechanism is as yet unknown and computational chemistry may be important to help unraveling it, provided the methods used are adequate, and the idea was that calculating the spectrum is a good check on the computational method. Of the model compound, [Fem(PyPepS)2r (see Figure 3-12) the spectrum in aqueous solution is known. 

They have been suggested as intermediates in acid-catalysed additions to nitriles. The hydration of nitriles probably involves initial protonation of the N end of the —C=N bond, as indicated by the nature of the product of the acid-catalysed reaction between acetonitrile and ethanol (Hill and Rabinowitz, 1926) (equation 36). 

The hydration of nitriles to form amides is promoted by metallic catalysts such as nickel and copper,9 and the copper catalyzed hydration has been utilized in an industrial process for the production of acrylamide from acrylonitrile.10 The hydration of... 

This Ru(II)-catalyzed hydration of nitriles is a highly useful transformation as demonstrated inter alia in the synthesis of (-)-pumiliotoxin C in a reaction sequence involving retro-aldol reaction, hydration, and cyclization (Scheme 10.9) [13]. 

Dimethylsulfoxide was found to increase the rate of hydrolysis in esters which were resistant to saponification. Treatment of alkyl toluenesulfonates with sodium naphthalene anion radical in tetrahydrofuran constituted an almost ideal procedure for regenerating the corresponding alcohols. The hydration of nitriles to amides in the presence of nickel catalysts shows an increase in yield with the addition of pyridine. ... 

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