Catalysts with nitrogen—hydrogen bond

The structure of the catalyst as determined by 13C NMR involves the bonding of binaphthol to the metal through oxygen atoms along with two hydrogen bonds to the nitrogen of the trimethyl piperidine as shown below [164],... 

Nitriles. Nitriles can be prepared by a number of methods, including ( /) the reaction of alkyl haHdes with alkaH metal cyanides, (2) addition of hydrogen cyanide to a carbon—carbon, carbon—oxygen, or carbon—nitrogen multiple bond, (2) reaction of hydrogen cyanide with a carboxyHc acid over a dehydration catalyst, and (4) ammoxidation of hydrocarbons containing an activated methyl group. For reviews on the preparation of nitriles see references 14 and 15. 

Shaw concluded that hydrogenation of 3-alkyl-4-aminomethylene isoxazol-5-ones (184) in the presence of palladium catalyst resulted in the saturation of either the endocyclic double carbon-nitrogen bond or the exocyclic double C—C bond with the retention of the heterocyclic nitrogen-oxygen bond. Recent data reported by Kochetkov et al. on the properties, and in particular on hydrogenation, of isoxazolid-5-ones - indicate, however, that Shaw had probably ob-... 

The use of chiral amide ligands has been restricted to rhodium, where the catalyst precursor is [Rh(BH4)(amide)py2Cl2]. The work has been reviewed (10, 35) cinnamate derivatives were reduced to up to 57% ee, and hydrogenation of a carbon- nitrogen double bond in folic acid leads to tetrahydrofolic acid with high biological activity (308). 

Control of the multitude of pathways which feed molecules can take is the primary objective of aU catalyst and process developments. The work covered in this chapter focuses primarily on describing the approaches in material and catalysis development which have led to major advances in zeolite application in hydrocarbon conversion. The breaking and formation of carbon-carbon and carbon-hydrogen bonds constitute the majority of the chemical transformations involved here with the less prevalent, but very important, breaking of carbon bonds with sulfur, nitrogen and oxygen taking place in parallel. 

The reaction is exothermic, hence the highest equilibrium yield is obtained at low temperatures and high pressures. The catalyst functions by inducing the formation of a nitrogen complex with the catalyst surface this complex is far more readily hydrogenated to NH3 than is nitrogen with its triple bond (Somorjai and Salmeron, 1986). 

Tsogoeva and co-workers explored the catalytic potential of pyridyl- and imida-zoyl-containing thiourea derivatives (e.g., thiourea 92 and 93) in the asymmetric model Strecker reactions [157] of N-benzyl- and benzhydryl-protected benzaldi-mine with HCN [258], The observed enantioselectivities were consistently very low (4—14% ee) for all catalyst candidates and were far below synthetically useful levels, while imidazoyl-thiourea 93 was reported to be highly active and displayed 100% conversion (at 7% ee) of the N-benzhydryl-protected benzaldimine (Scheme 6.99). X-ray structure analysis of a pyridyl-thiourea revealed an intramolecular hydrogen-bond between the basic ring nitrogen and one amide proton. This could make this... 

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