Amine To nitrile

The nickel hydroxide electrode resembles in its applications and selectivity the chemical oxidant nickel peroxide. The nickel hydroxide electrode is, however, cheaper, easy to use and in scale-up, and produces no second streams/ waste- and by-products [196], Nickelhydroxide electrode has been applied to the oxidation of primary alcohols to acids or aldehydes, of secondary alcohols to ketones, as well as in the selective oxidation of steroid alcohols, cleavage of vicinal diols, in the oxidation of y-ketocarboxylic acids, of primary amines to nitriles, of 2,6-di-tert-butylphenol to 2,2, 6,6 -tetra-rert-butyldiphenoquinone, of 2-(benzylideneamino)-phenols to 2-phenyloxazols, of 1,1-dialkylhydrazines to tetraalkyltetrazenes. For details the reader is referred to Ref. [195]. 

For the dehydrogenation of CH—XH structures, for example, of alcohols to ketones, of aldehydes to carboxylic acids, or of amines to nitriles, there is a wealth of anodic reactions available, such as the nickel hydroxide electrode [126], indirect electrolysis [127, 128] (Chapter 15) with I , NO, thioanisole [129, 130], or RUO2/CP [131]. Likewise, selective chemical oxidations (Cr(VI), Mn02, MnOJ, DMSO/AC2O, Ag20/Celite , and 02/Pt) [94] are available for that purpose. The advantages of the electrochemical conversion are a lower price, an easier scale-up, and reduced problems of pollution. 

Scheme 5 Mediated anodic oxidation of amine to nitrile and carbonyl compound.

Indirect electro-oxidation of primary amines to nitriles is achieved using halogen ion as mediator [93]. The reaction is typically carried out in an undivided cell... 

Silver(ll) oxide, present on a silver anode in aqueous alkali, will also cany out the oxidation of primary amines to nitriles. Oxidation of the intermediate imine at the silver anode is however relatively slow so that hydrolysis to the aldehyde becomes an important side reaction [97], a-Amino acids give nitriles in good yields at the silver(li) oxide electrode. 

A useful example is the oxidative dehydrogenation of primary amines to nitriles. The amine (2 mmol) is added dropwise or in small portions to a vigoronsly stirred solutuion of [RnO ] prepared as above (100 cm ) the reaction is complete when the dark orange colonr of [RuO ] reappears. The solution is extracted with dieth-ylether (3x25 cm ), dried over MgSO and the ether removed [549]. 

Abstract This chapter principally concerns oxidations of organic substrates containing N, O, S, P, As and Sb. Oxidations of amines are covered first, including primary amines to nitriles or amides secondary amines to imines or other products tertiary amines to N-oxides or other prodncts (Section 5.1) and the oxidation of amides (5.2). Oxidation of ethers to esters or lactones follows (5.3), then of sulfides to sulfoxides or sulfones (5.4) and of phosphines, arsine and stibines to their oxides (5.5). A final section (5.6) concerns such miscellaneous oxidations not covered by other sections in the book. 

The subject of Ru-catalysed amine oxidations has been reviewed [1-7]. The first catalytic oxidation (1978) used RuCl3/02/water-toluene/100°C to oxidise primary and secondary amines to nitriles and imines respectively [8]. 

Table 13. Oxidation of primary a-unbranched amines to nitriles at the nickel hydroxide electrode...

The Addition of Ammonia or Amines to Nitriles /V-Hydro-C-amino-addftion... 

RuHAP [13] and Ru/A1203 [14] catalysts were also able to oxidize primary amines to nitriles in high yield using 02 as an oxidant (Scheme 5.3). 

A considerable amount of work has been published dealing with the electro-oxidation of organics at Ni anodes in aqueous base [548-552], These reactions have generally been dehydrogenations, e.g. primary alcohols to aldehydes, secondary alcohols to ketones and primary amines to nitriles. The reactions occur on a relatively thick layer of oxide on the Ni anodes. Pletcher and co-workers [529, 548, 549] observed that most of the oxidizable compounds were found to oxidize at the same potential and this potential coincided with that at which the surface of the Ni became oxidized. A typical cyclic voltammogram recorded at Ni in dilute KOH in the presence and absence of n-propylamine is shown in Fig. 23. It can be seen that addition of n-propylamine results in an oxidation wave being observed which is... 

It is well known that the addition of ammonia or amines to nitriles leads to formation of various amidines 32 this type of oligomerization can be applied to the synthesis of heterocycles. On heating in the presence of sodium amide (or benzenesulfonic acid in some cases), o-cyanoaniline produces a mixture of the quinazoline (18) by dimerization and the tricycloquinazoline (19) by trimerization the trimer is obtained when the dimer is heated with another molecule of the monomer and sodium amide at 300°. The mechanism of this condensation has been reviewed.33... 

Many reagents convert primary amines into nitriles. Some of these have been mentioned above and represent serious limitations on methods for generating carbonyl compounds. Other ways of oxidizing amines to nitriles are the use of nickel peroxide,lead tetraacetate," copper(I) chloride plus oxygen and pyridine," iodine pentafluoride and benzeneseleninic anhydride. double bromination-dehy-drobromination can be effected for the preparation of nitriles with 2 equiv. of NBS and trimethyl-amine. Likewise, fluorination and elimination of HP gives nitriles." ... 

The heterobimetallic complexes [N(n-Bu)4] [Os(N)R2(/u.-0)2Cr02] catalyze the selective oxidation of alcohols with molecular oxygen. A mechanism in which alcohol coordinates to the osmium center and is oxidized by B-hydrogen elimination (see -Hydride Elimination) is consistent with the data. The hydroxide adduct of OSO4, [0s(0H)204], with ferric cyanide and other co-oxidants catalyzes the oxidative dehydrogenation of primary aromatic and aliphatic amines to nitriles, the oxidation of primary alcohols to carboxylic acids, and of secondary alcohols to ketones. Osmium derivatives such as OsCb catalyze the effective oxidation of saturated hydrocarbons in acetonitrile through a radical mechanism. ... 

Heterogeneous catalysts such as hydroxyapatite-bound Ru complex [67] and Ru/ AI2O3 [68] can be also used for the aerobic oxidation of primary amines to nitriles (Eqs. 3.32 and 3.33). 

Oxidations by oxygen and catalysts are used for the conversion of alkanes into alcohols, ketones, or acids [54]-, for the epoxidation of alkenes [43, for the formation of alkenyl hydroperoxides [22] for the conversion of terminal alkenes into methyl ketones [60, 65] for the coupling of terminal acetylenes [2, 59, 66] for the oxidation of aromatic compounds to quinones [3] or carboxylic acids [65] for the dehydrogenation of alcohols to aldehydes [4, 55, 56] or ketones [56, 57, 62, 70] for the conversion of alcohols [56, 69], aldehydes [5, 6, 63], and ketones [52, 67] into carboxylic acids and for the oxidation of primary amines to nitriles [64], of thiols to disulfides [9] or sulfonic acids [53], of sulfoxides to sulfones [70], and of alkyl dichloroboranes to alkyl hydroperoxides [57]. 

Nickel peroxide, an undefined black oxide of nickel, is prepared from nickel sulfate hexahydrate by oxidation in alkaline medium with an ozone-oxygen mixture [929] or with sodium hypochlorite [930, 931, 932, 933]. Its main applications are the oxidation of aromatic side chains to carboxyls [933], of allylic and benzylic alcohols to aldehydes in organic solvents [929, 932] or to acids in aqueous alkaline solutions [929, 930, 932], and of aldehydes to acids [934, the conversion of aldehyde or ketone hydrazones into diazo compounds [935] the dehydrogenative coupling of ketones in the a positions with respect to carbonyl groups [931] and the dehydrogenation of primary amines to nitriles or azo compounds [936]. 

Potassium ruthenate, K2RUO4, is prepared in situ from ruthenium trichloride and aqueous persulfate. The reagent catalyzes persulfate oxidations of primary alcohols to acids, secondary to ketones, and primary amines to nitriles or acids at room temperature in high yields [196],... 

The above nucleophilic addition reactions involve N—C bond formation, a bond that can also be created by insertion (at least formally) of a nitrile into a metal-N bond.148-150 Stereochemical and kinetic4,8 studies have been reported, although with few examples, for the addition of amines to nitriles at Pt11 centers, and the latter are indicative of the involvement, similar to the addition of alcohols (see above), of cyclic 4- and 6-center transition states, with one or two amine molecules, respectively, interacting with N=C. 

The usual ways to obtain amidines (or amides after subsequent hydrolysis) by addition of primary or secondary amines to nitriles are ... 

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