Carbon-nitrogen bonds conversion

The copper catalyzed formation of carbon-nitrogen bonds was exploited in the conversion of 2-(3 -aminopropyl)-bromobenzene to tetrahydro-isoquinoline (4.17.), The coupling, which proceeded readily already at 40 °C in the presence of diethyl salicylamide, was also efficient in the formation of dihydroindole derivatives.20... 

Oxidative reactions at carbon predominate in the biotransformation of cyclic amiiies, and an important consequence of this is often the cleavage of the carbon-nitrogen bond. For example, A-dealkylation of N- alkyl substituted pyrrolidine (or piperidine, morpholine, etc.) involves an initial oxidative attack at the a- alkyl carbon atom to yield an N hydroxyalkyl derivative (carbinolamine), which is then metabolized to a secondary amine and the corresponding aldehyde. The metabolic conversion of nicotine to nornicotine (30 see Scheme 3) probably involves this mechanism, although the iminium ion (31) has also been suggested as an intermediate in the biotransformation (76JMC1168). Carbinolamines are unstable intermediates and have been identified only in a few cases, e.g. A-hydroxymethylcarbazole... 

The imino nitrogen atom is sufficiently nucleophilic to attack the carbon atom of the seleniranium intermediate. An interesting example of these reactions is the conversion of imidates into y-lactams reported by Toshimitsu and Uemura [88-90] and by other authors [91,92] which is illustrated in Scheme 24. The cyclization of 155 occurs through the formation of a carbon-nitrogen bond with the generation of the iminium salt 156. The success of this reaction is due to the use of PhSeBr as the selenenylating agent. In this way, in fact, the bromine... 

Deamination via sulphonamide intermediates allows the conversion of the carbon-nitrogen bond into the carbon-oxygen bond. Conditions have been established such that nitrates may be obtained from the deamination of primary amines with dinitrogen tetroxide at low temperature rather than alcohols/ The oxidation of amines to nitriles has been carried out using copper(l) chloride in pyridine under an oxygen atmosphere/ which is a milder reagent than those previously used to perform this transformation. Cleavage of tertiary amines with ethyl chloroformate affords a simple preparation of di- and tri-substituted olefinic synthons (Scheme... 

Biotin apotranscarboxylase synthetase catalyzes the formation of the 6-N-(+)-biotinyl-L-lysyl carbon-nitrogen bond in methylmalonyl CoA oxaloacetic transcarboxylase. The conversion of the apoenzyme into the holoenzyme requires biotin, ATP, and Mg. A (H-)-biotinyl-5 -AMP enzyme complex seems to be formed in the course of that reaction (see Fig. 4-14). 

Elements such as oxygen, nitrogen, fluorine, and chlorine are more electronegative than carbon, so a carbon atom bonded to one of these atoms has a partial positive charge ( -1-). Conversely, metals are less electronegative than... 

One-electron oxidation of the vinylidene complex transforms it from an Fe=C axially symmetric Fe(ll) carbene to an Fe(lll) complex where the vinylidene carbon bridges between iron and a pyrrole nitrogen. Cobalt and nickel porphyrin carbene complexes adopt this latter structure, with the carbene fragment formally inserted into the metal-nitrogen bond. The difference between the two types of metalloporphyrin carbene, and the conversion of one type to the other by oxidation in the case of iron, has been considered in a theoretical study. The comparison is especially interesting for the iron(ll) and cobalt(lll) carbene complexes Fe(Por)CR2 and Co(Por)(CR2) which both contain metal centers yet adopt... 

Titanium silicate molecular sieves not only catalyze the oxidation of C=C double bonds but can be successfully employed for the oxidative cleavage of carbon-nitrogen double bonds as well. Tosylhydrazones and imines are oxidized to their corresponding carbonyl compounds (243) (Scheme 19). Similarly, oximes can be cleaved to their corresponding carbonyl compounds (165). The conversion of cyclic dienes into hydroxyl ketones or lactones is a novel reaction reported by Kumar et al. (165) (Scheme 20). Thus, when cyclopentadienes, 1,3-cyclohexadiene, or furan is treated with aqueous H202 in acetone at reflux temperatures for 6 h in the presence of TS-1, the corresponding hydroxyl ketone or lactone is obtained in moderate to good yields (208). 

From the recent advances the heteroatom-carbon bond formation should be mentioned. As for the other reactions in Chapter 13 the amount of literature produced in less than a decade is overwhelming. Widespread attention has been paid to the formation of carbon-to-nitrogen bonds, carbon-to-oxygen bonds, and carbon-to-sulfur bonds [29], The thermodynamic driving force is smaller in this instance, but excellent conversions have been achieved. Classically, the introduction of amines in aromatics involves nitration, reduction, and alkylation. Nitration can be dangerous and is not environmentally friendly. Phenols are produced via sulfonation and reaction of the sulfonates with alkali hydroxide, or via oxidation of cumene, with acetone as the byproduct. 

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 first step is strongly endothermic and is the main hurdle to overcome in the hydrogenation of nitrogen to ammonia. Conversely, the reverse reaction, which is the dehydrogenation of diimide, is strongly exothermic. Therefore we may expect that diimide will have a pronounced tendency to revert to molecular nitrogen. This is in fact so and, at normal temperatures, diimide exists only as a transient intermediate that cannot be isolated. It is extremely reactive and readily transfers hydrogen to carbon-carbon multiple bonds ... 

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