Unsaturated nitriles formation

One development involves the use of vitamin B 2 to cataly2e chemical, in addition to biochemical processes. Vitamin B 2 derivatives and B 2 model compounds (41,42) cataly2e the electrochemical reduction of alkyl haUdes and formation of C—C bonds (43,44), as well as the 2inc—acetic acid-promoted reduction of nitriles (45), alpha, beta-unsaturated nitriles (46), alpha, beta-unsaturated carbonyl derivatives and esters (47,48), and olefins (49). It is assumed that these reactions proceed through intermediates containing a Co—C bond which is then reductively cleaved. 

The presence of ammonia during hydrogenation suppresses formation of secondary amines and inhibits hydrogenation of double bonds in unsaturated nitriles. Eatty amines are used as corrosion inhibitors, flotation agents, quaternary salts for sanitizing agents and textile fabric softeners, and surface-active agents. 

The most important chemistry of azidoazoles is the fragmentation of derived nitrenes of which the prototypes are (453) (454) and (455) (456). Thus 5-azido-l,4-diphenyltriazole (457) evolves nitrogen at 50 °C (70JOC2215). 4-Azido-pyrazoles and -1,2,3-triazoles (458) undergo fragmentation with formation of unsaturated nitriles (8lAHC(28)23l). 

Thermolysis of 4- and 5-azidopyrazoles has been studied by Smith (B-70MI40402, 81AHC(28)232). These compounds undergo fragmentation with formation of unsaturated nitriles via the nitrenes (474a) and (474b Scheme 42). 

The catalytic conditions (aqueous concentrated sodium hydroxide and tetraalkylammonium catalyst) are very useful in generating dihalo-carbenes from the corresponding haloforms. Dichlorocarbene thus generated reacts with alkenes to give high yields of dichlorocyclopropane derivatives,16 even in cases where other methods have failed,17 and with some hydrocarbons to yield dicholromethyl derivatives.18 Similar conditions are suited for the formation and reactions of dibromocar-benc,19 bromofluoro- and chlorofluorocarbene,20 and chlorothiophenoxy carbene,21 as well as the Michael addition of trichloromethyl carbanion to unsaturated nitriles, esters, and sulfones.22... 

Much of the early work into the rhodium(II)-catalysed formation of oxazoles from diazocarbonyl compounds was pioneered by the group of Helquist. They first reported, in 1986, the rhodium(II) acetate catalysed reaction of dimethyl diazomalonate with nitriles.<86TL5559, 93T5445, 960S(74)229> A range of nitriles was screened, including aromatic, alkyl and vinyl derivatives with unsaturated nitriles, cyclopropanation was found to be a competing reaction (Table 3). 

Keto ester 67 was converted to the unsaturated nitrile 70 in a routine manner. The latter proved to be an exceptionally useful intermediate. Concern that the significant steric demands which are associated with the formation of a sigma bond to the fully substituted beta carbon of the unsaturated nitrile would prevent reaction from occurring, were allayed by the discovery that the controlled potential reduction of 70 at —2.4 V in the presence of dimethyl malonate as the proton donor, alforded a 90% isolated yield of the requisite [3.2.1] adduct 71. This material was subsequently converted to enone 72 [42], a convergent point with an existing synthesis of quadrone (59). 

As indicated by the conversion of 70 to 71, the electroreductive cyclization reaction provides as excellent method for the assembly of the bicyclo[3.2.1]oc-tane ring system. Several additional examples are portrayed in the following equations. In general, the use of an unsaturated nitrile rather than the corresponding ester is preferred, as this precludes lactone formation, and therefore... 

In the presence of various metal ions, 2-(fluoroenone)benzothiazoline has been found to rearrange to A-2-mercaptophenylenimine, while a free radical mechanism involving the homolysis of C-S and C-N bonds has been invoked to explain the formation of 3-phenyl-1,2,4-triazole derivatives from the thermal fragmentation and rearrangement of 2-(arylidenehydrazino)-4-(5//)-thiazolone derivatives. The cycloadducts (36) formed from the reaction of 3-diethylamino-4-(4-methoxyphenyl)-5-vinyl-isothiazole 1,1-dioxide (34) with nitric oxides or miinchnones (35) have been found to undergo pyrolytic transformation into a, jS-unsaturated nitriles (38) by way of pyrrole-isothiazoline 1,1-dioxide intermediates (37). 

The mechanism of these MCRs, according to [70], should include formation of unsaturated nitrile, its treatment with aminopyrazole and cyclization following with water elimination and, sometimes, oxidation (Scheme 17). 

The third variant employed an ce./J-unsaturated nitrile as electrophile1078. The addition of compound 740 to a-methylcinnamonitrile at — 78 °C led to the formation of a... 

Carbonylation of [CoH(CN)5]3- in strongly alkaline media results in the formation of [Co(CN)2-(CO)2]2- and the intermediacy of the short-lived tetracyanocobaltate(I) ion [Co(CN)4]3" in this process has been inferred from mechanistic studies (Scheme 9).15 Under very similar conditions [CoH(CN)s]3- catalyzes the cyanation of vinyl halides to form a,j3-unsaturated nitriles with retention of configuration (equation 6). Oxidative addition of vinyl halide to the intermediate [Co(CN)4]3- ion is stereoselective and in the a complex so produced reductive coupling of the vinyl and cyano ligands gives the stereoretentive organic product and regenerates [Co(CN)4]3-.78... 

Unsaturated nitriles prepared by the dehydration of amides include 1-cyano-1-alkynes, e.g. 1-cyano-l-heptyne (85%), and 1-cyano-l-alkenes, e.g. /3-isopropylacrylonitrile (80%). Some dehydrating agents such as phosphorus pentachloride may lead to the formation of halogen-containing products phosphorus pentoxide is preferred in these cases. In a comparison of methods for preparing olefinic nitriles, it has been shown that... 

Hydrostannation of highly polarized a,)8-unsaturated nitriles leads to the formation of N-stannylketenimines 31, 33) in what is considered to be a polar 1,4-addition. Thus, polar mechanisms are ascribed to reactions leading to either 1-cyanoalkyl or ketenimine adducts. 

The deuterium labelling established that the y, 5-unsaturated, nitrile 241 equilibrates at room temperature with the iV-allylketene imine 242 through an intramolecular rearrangement mechanism. Deuterium has been applied in the study of the novel palladium(0)-catalysed cyclization of 2,7-octadienyl carbonate containing an allylsilane moiety, 243, to product 244 (in 89%) and some 245 in the presence of phosphite 246 (equation 99). Intramolecular KlEs (Ah/Ad =3.0 and 3.5) have been observed in a bicyclic olefin formation (monoterpinene biosynthesis from [1- H,4- H2]- and [10- H2]-geranyl pyrophosphates) catalysed by pinene synthases from sage (Salvia officinalis). ... 

The trimethylsilyl group can rigorously control and direct the Beckmann fragmentation leading to the regio- and stereo-specific formation of unsaturated nitriles (equations 41 to 43). Oxime acetate (57) fragments to the cij-alkenic nitrile (58) in 90% yield, whereas its epimer (59) affords the franj-alkenic nitrile (60) in 94% yield under the same conditions. Furthermore, fluoride-induced fragmentation can re-... 

As with amine oxides and sulfoxides, acyclic 1,2-disubstituted alkenes are usually obtained with the ( )-stereochemistry, although the formation of a,(3-unsaturated nitriles is reported to give a mixture of ( )- and (Z)-isomers. For cyclic alkenes, the stereochemistry of double bond formation depends upon ring size. However, it can be affected by conformational factors, e.g. cyclododecyl phenyl selenide gives a mixture of cis- and fra/is-cyclododecenes on oxidative elimination (equation 38) but only the (El-isomer (101) was obtained from the acetoxycyclododecyl selenide (100 equation 39). ... 

The problems are due to the electrophilicity of the metal-carbene intermediates in these transformations, and to competitive, fast dihydropyrazole formation resulting from uncatalyzed thermal [3 + 2] cycloaddition of the diazo compound to the alkene furthermore, o , -unsaturated nitriles often yield 2-vinyloxazoles under the reaction conditions. 

There are only a few examples of cyclopropanes prepared via the addition of dichlorocarbene to alkenenitriles. Depending on the structure of the unsaturated nitrile, the chloroform/base/phase-transfer catalyst or dichlorohalomethyl(phenyl)mercury methods are used in the former case, the formation of the adducts of trichloromethyl anion competes considerably. Thus, acrylonitrile, but-2-enenitrile and 3-phenylpropenenitrile gave, by the phase-transfer catalytic method, Michael adducts exclusively. The same occurs if acrylonitrile reacts with trihalomethyl(phenyl)mercury and sodium iodide mixture. An example is the formation of 1 and... 

---