Unsaturated nitriles reaction

In a,)8-unsaturated nitriles, reaction can occur at a vinylogous methylene group, as in example 202, to give a 2-chloro-3-cyanopyridine (Eq. 162).Yields are poor, but are much better with the vinylogous cyanoacetates such as compound 203. Aminopyrimidines 204 can be obtained from arylcyanocarbonyl compounds, using formamide and phosphoryl chloride (Eq. 163). Yields, when quoted, are very poor. 

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]. 

Allylalion of the alkoxymalonitrile 231 followed by hydrolysis affords acyl cyanide, which is converted into the amide 232. Hence the reagent 231 can be used as an acyl anion equivalent[144]. Methoxy(phenylthio)acetonitrile is allylated with allylic carbonates or vinyloxiranes. After allylation. they are converted into esters or lactones. The intramolecular version using 233 has been applied to the synthesis of the macrolide 234[37]. The /i,7-unsaturated nitrile 235 is prepared by the reaction of allylic carbonate with trimethylsilyl cyanide[145]. 

The allyl cyanoacetate 731 can be converted into an a, /3-unsaturated nitrile by the decarboxylation-elimination reaction[460], but allyl malonates cannot be converted into unsaturated esters, the protonation and allylation products being formed instead. 

Reactions. The chemical properties of cyanoacetates ate quite similar to those of the malonates. The carbonyl activity of the ester function is increased by the cyano group s tendency to withdraw electrons. Therefore, amidation with ammonia [7664-41-7] to cyanoacetamide [107-91-5] (55) or with urea to cyanoacetylurea [448-98-2] (56) proceeds very easily. An interesting reaction of cyanoacetic acid is the Knoevenagel condensation with aldehydes followed by decarboxylation which leads to substituted acrylonitriles (57) such as (29), or with ketones followed by decarboxylation with a shift of the double bond to give P,y-unsaturated nitriles (58) such as (30) when cyclohexanone [108-94-1] is used. 

This reaction can be extended to unsaturated nitriles, eg, acrylonitrile, which can give trihalostannyl-functional carboxyHc acids, esters, and amides by the proper choice of solvents and reaction conditions (156). 

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. 

Powdered potassium permanganate (94 mg) is added to an ice-cold, stirred solution of 0.1 g of the unsaturated nitrile in 3.5 ml of acetone containing 0.11 ml of piperidine. The reaction mixture is stirred at 0° for 1.5 hr, allowed to warm to room temperature (30 min) and then treated with 0.02 ml of acetic acid in 0.2 ml of acetone. After stirring at room temperature for an additional 1.5 hr the mixture is treated with chloroform, aqueous sodium bisulfite and sufficient 1 N sulfuric acid to reduce all of the manganese dioxide. 

The titanium(IV) chloride catalyzed addition of allylic silanes to (E)-(2-nitroethenyl)benzene affords y,<5-unsaturated nitronates which, on treatment with low valent titanium species [generated in situ from titanium(IV) and zinc], give y,<5-unsaturated nitriles. For example, [(Zs)-2-butenyl]-(dimethyl)phenylsilane underwent reaction with ( )-(2-nitroethenyl)benzene to give 3-methyl-2-phenyl-4-pentenenitrile in 65 % yield as a 3 1 mixture of diastereomers of unassigned configuration22. 

Vinyl sulfones such as 262 are smoothly converted to a,) -unsaturated nitriles such as 263 on treatment with KCN in the presence of dicyclohexyl-18-crown-6 in refluxing t-butyl alcohol (equation 155)148. The reaction conditions are compatible with base-labile functionalities such as a methoxycarbonyl group (equation 156)148. This method can be used in the preparation of the sesquiterpene aldehyde nuciferal from allyl phenyl sulfones. 

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). 

Although the unsaturated nitrile oxides 124 can be prepared via the aldoxime route (see Scheme 8), the older procedure suffers from the disadvantage that a tenfold excess of allyl alcohol and two additional steps are required when compared to Scheme 15. Therefore, unsaturated nitro ether 123 that can be prepared by condensation of an aldehyde 120 and a nitro alkane followed by Michael addition of alcohol 122, was a useful precursor to nitrile oxide 124 [381. The nitrile oxide 124 spontaneously cyclized to ether 125. This procedure is particularly suitable for the synthesis of tetrahydrofurans (125a-h) and tetrahydropyrans (125i-k) possessing Ar substituents in 72-95% yield (Table 12). The seven-membered ether 1251 was obtained only in 30% yield on high dilution. The acetylenic nitro ether 126 underwent INOC reaction to provide the isoxazole 127. 

In 1989, Isayama and Mukaiyama reported a related Co-catalyzed coupling reaction that employs a,b-unsaturated nitriles, amides, and esters with PhSiLb as a hydrogen source [9]. Cobalt-bis(diketonato) complex, Co(II)(dpm)2 [dpm = bis(dipivaloylmethanato)] (5mol%), exhibited high catalytic activity at 20 °C in the coupling of excess acrylonitrile and ben-zaldehyde to provide b-hydroxy nitrile 4 in 93% yield (syn anti = 50 50) (Scheme 5). N,N-Dimethylacrylamide and methyl cinnamate both reacted... 

A new water soluble palladium(O) complex was also prepared. This compound and a previously reported related species were examined as catalysts in the hydrogenation of unsaturated nitriles in water. It was found that the pH of the solvent plays a crucial role in determining both yield and reaction course.869... 

The base-catalyzed joint reaction of nitroalkenes with thiophenol in the presence of aldehydes gives y-phenylthio-P-nitro alcohols in one pot (Eq. 4.5).8 The joint reaction of nitroalkenes with thiols and a,p-unsaturated nitriles (or esters) has also been achieved. (Eq. 4.6).9 P-Nitro sulfides thus prepared show unique reactivity toward nucleophiles or tin radicals. The nitro... 

EvenPd(OAc)2 is not effective in catalyzing the cyclopropanation of a,P-unsaturated nitriles by ethyl diazoacetate. Instead, vinyloxazoles 92 are formed from acrylonitrile or methacrylonitrile by carbenoid addition to the CsN bond 143 Diethyl maleate and diethyl fumarate as well as polyketocarbenes are by-products in these reactions the 2-pyrazoline which would result from initial [3 + 2] cycloaddition at the C=C bond and which is the sole product of the uncatalyzed reaction at room temperature, can be avoided completely by very slow addition of the diazoester... 

I.3.4.2.2. Nonaromatic Unsaturated Heterocycles Reactions of aromatic nitrile oxides with 1-azirines are followed by the ring opening of the latter to give 4-benzamidoisoxazoles 145 (314). The structure of 145 (R = 4-C1C6H4, Ar = Ar7 = Ph) was established by single-crystal X-ray analysis. A mechanism for the formation of 145 has been proposed, (see Scheme 1.29). 

Treatment of y-nitrothioamides 368 with phenyl isocyanate and triethylamine (nitrile oxide generation conditions) leads to a.j3-unsaturated nitriles 369. The mechanism proposed for this reaction is shown in Scheme 1.42, which includes the dehydration stage of the nitrile oxide formed (418). 

This aldol condensation is assumed to proceed via nucleophilic addition of a ruthenium enolate intermediate to the corresponding carbonyl compound, followed by protonation of the resultant alkoxide with the G-H acidic starting nitrile, hence regenerating the catalyst and releasing the aldol adduct, which can easily dehydrate to afford the desired a,/3-unsaturated nitriles 157 in almost quantitative yields. Another example of this reaction type was reported by Lin and co-workers,352 whereas an application to solid-phase synthesis with polymer-supported nitriles has been published only recently.353... 

Abstract This chapter presents the latest achievements reported in the asymmetric hydroformylation of olefins. It focuses on rhodium systems containing diphosphites and phosphine-phosphite ligands, because of their significance in the subject. Particular attention is paid to the mechanistic aspects and the characterization of intermediates in the hydroformylation of vinyl arenes because these are the most important breakthroughs in the area. The chapter also presents the application of this catalytic reaction to vinyl acetate, dihydrofurans and unsaturated nitriles because of its industrial relevance. 

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