Vinyl nitriles, synthesis

This procedure, which involves the addition of an anion derived from a nitrile to an unactivated acetylenic bond under rather mild conditions, is a convenient general method for the synthesis of a-vinyl-nitriles (see Table I). The reaction proceeds smoothly in either dimethyl sulfoxide or hexamethylphosphoric triamide (see p. 103 for warning) as solvent with a tetraalkylam monium salt as catalyst. The products thus prepared are obtained in yields higher2 than those obtained under conventional conditions, which generally require higher temperatures and elevated pressures.3-4... 

A single-mode microwave procedure has been reported for the palladium-catalyzed preparation of both aryl and vinyl nitriles from the corresponding bromides. The reaction times were short and full conversions were achieved in just a few minutes (Eq. 11.33) [50], The cycloadditions to yield the tetrazoles needed slightly longer reaction times, from 10 to 25 min, but only 20 W of power was required as a temperature of 220 °C was reached after 10 min heating. The yields in this step ranged from 36% to 96%. This method for transforming halides into tetrazoles has been used for the synthesis of a novel HIV-protease inhibitor [50],... 

Two new stereospecific syntheses of vinyl nitriles are reported. One involves the treatment of vinyl cuprates with cyanogen chloride (benzenesulphonyl cyanide or p-tosyl cyanide) in THF to give the vinyl nitriles in good yield (Scheme 16). The other synthesis comprises the conversion of vinyl halides into nitriles by direct... 

Recently, Renaud and coworkers reported a new, simple, and air-stable iron(II) complex pre-catalyst catalyzed synthesis of substituted pyridines via [2 -F 2 -F 2] cycloaddition between diynes and nitrile derivatives [50]. Alkyl-, aryl-, and vinyl nitriles could all be applied functionalized pyridines can be produced in high yields without any pre-reduction of the catalyst (Scheme 3.22). 

Unsaturated nitriles are formed by the reaction of ethylene or propylene with Pd(CN)2[252]. The synthesis of unsaturated nitriles by a gas-phase reaction of alkenes. HCN, and oxygen was carried out by use of a Pd catalyst supported on active carbon. Acrylonitrile is formed from ethylene. Methacrylonitrile and crotononitrile are obtained from propylene[253]. Vinyl chloride is obtained in a high yield from ethylene and PdCl2 using highly polar solvents such as DMF. The reaction can be made catalytic by the use of chloranil[254]. 

The reaction between benzylidenetriphenylphosphorane and benzonitrile has been reinvestigated and the primary product (82) isolated. Stable ylides react similarly with activated nitriles, e.g. cyanogen and trifluoro-acetonitrile, but cyanomethylenetriphenylphosphorane with methyl cyano-formate gave largely the vinyl ether (83), the product of a normal olefin synthesis on the carbonyl of the ester group. 

An important contribution to silylium ion chemistry has been made by the group of Muller, who very recently published a series of papers describing the synthesis of intramolecularly stabilized silylium ions as well as silyl-substituted vinyl cations and arenium ions by the classical hydride transfer reactions with PhjC TPEPB in benzene. Thus, the transient 7-silanorbornadien-7-ylium ion 8 was stabilized and isolated in the form of its nitrile complex [8(N=C-CD3)]+ TPFPB (Scheme 2.15), whereas the free 8 was unstable and possibly rearranged at room temperature into the highly reactive [PhSi /tetraphenylnaphthalene] complex. ... 

The hydroxyl group was usually protected, because cyanohydrins have tendency to racemization or even decomposition. Vinyl ethers or acetal and acid catalysts furnish acetals [62]. Trialkylsilyl chlorides and imidazole are used to give silyl ethers [63]. Commonly used protective groups are silyl ether, ester, methoxy isopropyl (MIP) ether, and tetrahydro-pyranyl ether. ( -Protected cyanohydrins are tolerant to a wider range of cyanide/nitrile transformations and are utilized widely in the synthesis of compounds of synthetic relevance in organic chemistry. 

A solid-phase synthesis of 3-substituted isoxazoles 31 in good yields and purities was achieved by 1,3-DC of polymer-supported vinyl selenide with in situ generated nitrile oxides treatment of intermediate isoxazolines 30 with an excess of hydrogen peroxide resulted in the release of isoxazoles 31 while the use of Mel/Nal led to 3-substituted 5-iodoisoxazolines... 

Anionic polymerization is a powerful method for the synthesis of polymers with a well defined structure [222]. By careful exclusion of oxygen, water and other impurities, Szwarc and coworkers were able to demonstrate the living nature of anionic polymerization [223,224]. This discovery has found a wide range of applications in the synthesis of model macromolecules over the last 40 years [225-227]. Anionic polymerization is known to be limited to monomers with electron-withdrawing substituents, such as nitrile, carboxyl, phenyl, vinyl etc. These substituents facilitate the attack of anionic species by decreasing the electron density at the double bond and stabilizing the propagating anionic chains by resonance. 

The stereoselective synthesis of the 12-acetoxy enone 428, related to the limonoid azadiradione, has been achieved in 12 steps (16% overall yield), starting from tricyclic diester 429. The key steps involve an intramolecular 1,3-dipolar cycloaddition of a nitrile oxide and a Stille coupling reaction of vinyl iodide with stannylfuran (469). 

Isoxazolines are partially unsaturated isoxazoles. In most cases these compounds are precursors to the isoxazoles, and as a result, the synthesis can also be found in Sect. 3.2.1b. Kaffy et al., used a 1,3-dipolar cycloaddition of a nitrile oxide (186) with the respective styrene (201a or b) to generate isoxazolines (202a or b, respectively). Depending on the substitution of the vinyl portion of the styrene molecule, either 3- or 4-substituted isoxazolines could be formed (Scheme 55) [94], Simoni et al. employed similar chemistry to produce isoxazolines [60]. Kidwai and Misra emplyed microwave technology to treat chalcones with hydroxylamine and basic alumina [99]. The isoxazoles synthesized by Simoni et al. possess anti-proliferative and apoptotic activity in the micromolar range [60]. 

This chapter mainly focuses on the latest achievements and recent developments in asymmetric hydroformylation. Since several reviews have been made in the last decade [9,14-16], the chapter discusses the contributions reported between 2000-2005 in particular, although the main diphoshites and phosphine-phosphite rhodium catalytic systems discovered since 1995 are also considered because of their significance in the subject. Particular attention is paid to mechanistic aspects and characterization of intermediates in the case of the hydroformylation of vinyl arenes because this is one of the most important breakthroughs in the area. The application of this catalytic reaction to different type of substrates, in particular dihydrofurans and unsaturated nitriles is the other main subject of this chapter because of their interest in organic synthesis and their industrial relevance. 

Uses Copolymerized with methyl acrylate, methyl methacrylate, vinyl acetate, vinyl chloride, or 1,1-dichloroethylene to produce acrylic and modacrylic fibers and high-strength fibers ABS (acrylonitrile-butadiene-styrene) and acrylonitrile-styrene copolymers nitrile rubber cyano-ethylation of cotton synthetic soil block (acrylonitrile polymerized in wood pulp) manufacture of adhesives organic synthesis grain fumigant pesticide monomer for a semi-conductive polymer that can be used similar to inorganic oxide catalysts in dehydrogenation of tert-butyl alcohol to isobutylene and water pharmaceuticals antioxidants dyes and surfactants. 

A new route to 4-substituted pyrimidines involves the condensation of nitriles with iV-vinyl amides which are activated by trifluoromethanesulfonic anhydride and 2-chloropyridine <2006JA14254>. The method is illustrated by the synthesis of 4-cyclohexyl-2,5-diphenylpyrimidine 627 from A-styrylbenzamide 625 and cyclohexanecarboni-trile 626 in 89% yield <2006JA14254>. 

Vinylpyrroles and vinylindoles are extremely sensitive to acid-catalyzed dimerization and polymerization and it is significant that much of the early research was conducted on systems which were produced in situ. Even by this approach, the dimerization of, for example, 2-(3-indolyl)propene and l-(3-indolyl)-l-phenylethylene was difficult to prevent (see the formation of 110 and 120, Section 3.05.1.2.8). Similarly, although it is possible to isolate ethyl 2-(2- and 3-indolyl)propenoates, they appear to be extremely unstable at room temperature even in the absence of acid (81UP30500) to give [ 4 + 2] cycloadducts of the type (348) (cf. 77JCS(P1)1204>. For many years simple vinylpyrroles also eluded isolation, on account of their facile acid-catalyzed polymerization. Application of the Wittig reaction, however, permits the synthesis of vinyl-pyrroles and -indoles under relatively mild and neutral conditions (see Section 3.05.2.5). In contrast, heteroarylvinyl ketones, esters, nitriles and nitro compounds, obtained by condensation of the appropriate activated methylene compound with the heteroaryl aldehydes (see Section 3.05.2.5), are thermally stable and... 

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