Nitriles formation from oximes

One-Pot Operations for Nitrile Oxide Formation From Oximes... 

Cycloadditions with monosubstituted oleflns proceed rapidly and regioselectively to yield the 5-substituted dihydroisoxazoles. Thus, addition of styrene to nitrile oxide 164, formed from oxime 163, results in the formation of the 5-phenyl- 165 and 4-phenyldihy-droisoxazoles 166 in a 99 1 ratio (equation 72) ° °. ... 

In the case of the oximes of the aldose sugars, the situation is more complicated because of the possibility of both open-chain and cyclic structures. That aldose oximes can react in the open-chain form follows from the formation of the nitriles and from the isolation of acylated open-chain aldose oximes as secondary products in preparation of nitriles. For example, Wolfrom and Thompson, by the action of sodium acetate-acetic anhydride on n-glucose oxime, not only obtained pentaacetyl-D-glucononitrile, in 40% yield, but also isolated a small amount of hexaacetyl-oWeAydo-D-glucose oxime (V) identical with that prepared by mild acetylation of pentaacetyl-aWe%do-D-glucose oxime (IV) whose structure was assured by its formation from pentaacetyl-aldehydo-D-glucoae (III). 

The nitrosation of aliphatic carbon atoms, particularly of carbon atoms activated by adjacent carbonyl, carboxyl, nitrile, or nitro groups, has been reviewed in great detail [2]. Judging from this review, with few exceptions, nitrosation of active methylene compounds leads to the formation of oximes (unfortunately termed isonitroso compounds in the older literature). The few exceptional cases cited in which true nitroso compounds (or their dimers) were formed involved tertiary carbon atoms in which no hydrogen atoms were available to permit tautomerism to the oxime or involved a reaction which was carried out under neither acidic nor basic conditions. 

Acetylation of phenols with simultaneous formation of nitriles from oximes s. U, 547... 

It is believed that SCR by hydrocarbons is an important way for elimination of nitrogen oxide emissions from diesel and lean-burn engines. Gerlach etal. [115] studied by infrared in batch condition the mechanism of the reaction between nitrogen dioxide and propene over acidic mordenites. The aim of their work was to elucidate the relevance of adsorbed N-containing species for the F>cNOx reaction to propose a mechanism. Infrared experiments showed that nitrosonium ions (NO+) are formed upon reaction between NO, NOz and the Brpnsted acid sites of H—MOR and that this species is highly reactive towards propene, forming propenal oxime at 120°C. At temperatures above 170°C, the propenal oxime is dehydrated to acrylonitrile. A mechanism is proposed to explain the acrylonitrile formation. The nitrile can further be hydrolysed to yield... 

Another type of reductive amination is shown in Figure 13-18. This reaction illustrates the formation of an amine from a ketone through the formation of an intermediate oxime. Figure 13-19 shows the conversion of a nitrile to an amine. (The nitrile can be formed by the action of cyanide ion, CN", on a halide via an Sf 2 mechanism.)... 

The formation of a very electrophilic intermediate 258 from 256 and 257 is proposed (equation 78). The hydroxyl group of the oxime adds to 259, giving a reactive cationic species 260 that rearranges and affords the nitrile 261 (in the case of aldoxime, equation 79), or the amide 262 upon hydrolytic workup (equation 80). The conversion of 260 to the nitrilium ion should occur through a concerted [1,2]-intramolecular shift. This procedure can be applied in the conversion of aldoximes to nitriles. It was observed that the stereochemistry of the ketoximes has little effect on the reaction, this fact being explained by the E-Z isomerization of the oxime isomers under the reaction conditions. 

Fragmentation of the intermediate or concerted formation of nitriles from the activated oxime (Scheme 9, pathway 3) this is the Beckmann fragmentation. In some circumstances this pathway becomes dominant, particularly when there are quaternary carbons adjacent to the oxime. This transformation has found particular utility in ring-cleavage processes (sometimes called abnormal or second-order Beckmann rearrangements). 

Oxidation of silyl tosylhydrazones (35) in an aprotic medium (dichloromethane) also results in the formation of nitriles, but in this case the conversion is apparently a true anodic process41 in which the key difference from the anodic behavior of oximes is the presence of the p-toluensulfonyl group, which facilitates cleavage of the N—N single bond (equation 20). 

Oximes derived from p-silyl and P-stannyl ketones undergo unusual Beckmann rearrangement, giving rise to nitriles as predominant products. For example, Beckmann rearrangement of 3-trimethylsilylcyclohexanone oxime 88 (Scheme 15) proceeds to the formation of the acyclic alkenyl nitrile 89 as the major product.90 The nitrile is believed to be formed by fragmentation of the protonated oxime, giving the P-silyl—stabilized cation 90, followed by desilylation. Our... 

Direct dehydrogenation of oximes is also possible, particularly for sterically hindered nitrile oxides. The most successful oxidizing agents are alkaline hypobromite and NBS in the presence of base, the latter being valuable when basic groups are present. Lead tetraacetate and alkaline hypochlorite have also been employed, but the yields are lower. The formation of furoxans from the reaction of alkoximes with nitrogen oxides is believed to proceed via the corresponding nitrolic acids. 

Whenever the formation of the chano form was allowed, the appropriate consequences were observed (1), e.g., formation of cfomoajmaline oxime, mp 220°, and from it by dehydration the corresponding nitrile, mp 254°-255°, [a]D + 29° (CHCI3) Wolff-Kishner reduction of ajmaline to deoxydihydrocforooajmaline, mp 185°-186°, [a]D + 39° (CHCI3) reduction of ajmaline with potassium borohydride to furnish dihydro-cfccmoajmaline, mp 200° (34) formation of 21-alkylaminoisoajmaline derivatives by heating ajmaline with primary amines (35) and epi-merization of ajmaline in the presence of alkali to the more stable isomer isoajmaline (1). 

Treatment of oximes with LAH in HMPA does not afford the expected amine products, but rather gives ketones from ketoximes and nitriles and/or aldehydes from aldoximes. These unusual results are attributed to the formation of imine intermediates which are hydrolyzed to carbonyls or undergo elimination to nitriles (which may be further reduced and hydrolyzed to aldehydes). ... 

Applications in organic synthesis of the iminoacylation reaction of oximes have recently been found at kinetically labile Zn11- or Con-oxime systems. The former catalyzes the hydrolysis of nitriles to carboxamides (23)37 and the Co11 system catalyzes the conversion of nitriles into amidines (24) (also involving C N bond formation upon reaction with ammonia, formed from competitive hydrolysis of the nitrile).110... 

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