Nitriles and Isonitriles

Carbon-13 shifts of cyano groups in nitriles are found between 110 und 125 ppm (Table 4.46) [77 a, 352]. Shift values close to 125 ppm are characteristic of nitriles with a branched alkyl groups (Table 4.46). Similiar to the isoelectronic ethynyl group, the nitrile function shields the oc carbon owing to the anisotropy effect. Alkenyl carbon shifts of 

The simplest nitrile, HCN, reacts with COF and HF at room temperature, via the intermediate isocyanate, according to [632]  

REACTIONS OF NITRILES WITH COFj OVER MERCURY CATALYSTS [1524] 

Only small yields of product are formed and, again, the isocyanate is presumably formed via the intermediate, CF3CF=NC(0)F. However, the reaction between RCN and COFj can be catalysed over HgO (or HgFj) catalysts at 50-130 C to give RCF NCO [1524] in good yields. Table 13.25. 

The reaction of 4-N02CgH C=N with COFj resulted in the formation of the carbamoyl fluoride, 4-NO jCgH4CF=N-C(0)F, rather than the isocyanate [2032]. 

The radical anion generated from propanenitrile (by abstraction of the two 1-hydrogen atoms of the nitrile with [0] ) reacts slowly with COFj to eliminate HF [469], but provided no definite conclusion regarding the structure of [CjHjCN] . 

The longest wavelength absorption of alkyl cyanides is a weak band in the vacuum uv possibly originating from an it transition of the triple bond system  

The gas phase photolysis of acetonitrile at 1849 A showed that two primary processes occur, viz. 

The photolysis of the leucocyanides of the triphenyl methane dyes in polar solvents proceeds to ionic products, viz. 

Methyl isocyanide undergoes homogeneous unimolecular isomerization to acetonitrile, and the limiting rate coefficient is given by  

Potential surfaces for the isocyanide-cyanide rearrangement have been constructed from extended Hiickel calculations and theory predicts a small amount of charge separation in the transition state . The data on methyl and ethyl iso- 

Following the determination of the hydrolytic rate constants of an epimeric pair of tricyclic nitriles (78) by a non-linear, least-squares fitting method, a novel eigenvalue-eigenvector analysis of the sensitivity coefficients permitted maximization of the kinetic dataJ  

Selective nucleophilic attack of one or both of the cyano groups of aryl dicyanooxi- 

The alkaline hydrolysis of a sulfonylurea herbicide, A - [(4,6-dimethoxy-2-pyrimidinyl)amino]carbonyl -l-methyl-4-(2-methyl-2//-tetrazol-5-yl)-l//-pyrazole-5-sulfonamide (azimsulfuron) (87) yields, via attack at the carbonyl group, two products, the bicyclic sulfonamide (88) and 2-amino-4,6-dimethoxypyrimidine (89). An alternative reaction pathway is via deprotonation of the sulfonamidic proton, but this possibility was not discussed. 

The kinetics and mechanism of alkaline hydrolysis of Af-tolylbenzohydroxamic acids (90 X = H, Me, Cl) in aqueous dioxane have been reported. A study of the effect of solvents on the mechanism of the acid hydrolysis of N-phenylbenzohydroxamic acid (91) has revealed that methanol and dioxane have a rate-enhancing effect, but DMF, acetone, EtOH, and propan-2-ol exert a rate-decreasing effect. The alkaline hydrolysis in aqueous dioxane of N-p-tolylcinnamohydroxamic acid (92) proceeds via initial rate-limiting formation of a tetrahedral intermediate.  

Thermolysis of A-acetylpropanamide (93) has been investigated using a hybrid d-functional theory (DFT) B3LYP method and shown to occur by two mechanisms, methyl-proton transfer and methylene-proton transfer, the activation barrier for the former being lower than that of the latter. A review (37 references) of recent examples of ring-opening reactions of succinimides (94) has covered alcoholysis, aminolysis, and reactions with carbon nucleophiles.  

Because of the symmetrical electron distribution around the nitrogen atom, the C-coupling can be observed in the NMR spectra of isonitriles, leading to triplets with intensities of 1 1 1 (spin quantum number of 1=1, natiunl abundance, 

As in other fields of polar organometallic chemistry, the (commercial) availability of strongly basic reagents and the increased knowledge about their interaction with organic compounds have considerably stimulated the chemistry of nitriles and isonitriles. 

Before 1960, only sodamide and potassium amide were used for the a-metallation of nitriles ( CH—C=N) and successful couplings with electrophiles were restricted to alkylations [la]. The extension of the number of base-solvent systems allowed a clean a-metallation of a variety of nitriles and the subsequent successful reaction with other nucleophiles [lb]. The use of a-metallated dialkyl-aminonitriles R2NCH(R )C=N and protected cyanohydrins R CH(C=N)OR (R = SiMe3 or CH(CH3)OEt) as acyl-anion equivalents in organic synthesis has been reviewed by Albright [2]. 

The procedures in Sect. 4 give some representative examples of metallation of nitriles and isonitriles and reactions of the anionic intermediates with alkylating agents, epoxides, aldehydes, and ketones. Syntheses involving the generation of anionic intermediates (mostly in small concentrations) and their immediate further reaction with an electrophile present in the medium during this generation fall beyond the scope of this book. 

Cope AC, Holmes HL, House HO (1957) Org Reactions 9 107, John Wiley b. Arseniyadis S, Kyler KS, Watt DS (1984) Org Reactions 31 1, John Wiley 

Schollkopf U (1979) New Synthetic Methods, Vol 6, Verlag Chemie, Weinheim p 99 

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The addition of hydrazoic acid to carbon—nitrogen unsaturated bonds as in hydrogen cyanide, nitriles, and isonitriles leads to unsubstituted, 5-, or... 

The reaction of matrix-isolated triazidophenylsilane with r-BuOH led to the formation of /V-(di-f-butoxysilyl)aniline and amino(di-r-butoxy)phe-nylsilane, the trapping products of the nitrile and isonitrile.6... 

Nitrogenases are very versatile enzymes. They reduce, in addition to N2, a lot of other substrates, for example, protons, acetylene, azide, nitriles, and isonitriles. All of these substrates are reduced by multiples of [2 H+/2 e ] reductions. Both CO and NO inhibit nitrogenase activity. The apparent [2 H+/2 e ] multiplicity of substrate reductions and a couple of other findings strongly suggest diazene and hydrazine to be intermediates of the N2 —> NH3 reduction. 

The THT and SMe2 adducts have structures of the type (18-B-V). Their chemistry has been extensively studied and it is summarized in Fig. 18-B-7. The diverse, and in some cases unique, reactivity of these compounds includes substitution with preservation of the geometry or with conversion to (MX4)2(/t-X)2 species, oxidative-addition,53 cluster formation, splitting of C—N bonds,54 and above all coupling of the molecules with triply bonded carbon atom.55 They catalytically trimerize and polymerize terminal acetylenes, and dimerize nitriles and isonitriles with incorporation of the new ligand into the complex. Another remarkable reaction of M2C16L3 is the metathesis of M=M and N=N bonds into two M=N bonds upon reaction with azobenzene. 

The four-membered ring Zr systems (24) can undergo further ring expansion reactions with other chalcogenides, nitriles, and isonitriles (Scheme 9). ... 

Fluorine-substituted quinolines can be formed in good yields from readily available starting materials. The reaction proceeds by generating nucleophiles through addition to multiple bonds, in this case, nitriles and isonitriles <03OL1455>. 

Complex hydride reductions of Nj, N O, [CN] and nitriles in reactions containing complex mixtures of metal-ion species produce N—H bonded products " by reactions that may relate to those of the biological nitrogenases". Complete reaction stoichiometries are not well established. These reactions are not competitive with other methods for NH or amine synthesis. Nitrogen reacts in H O with a mixture of NaBH, S-donor ligands (e.g., NH CjM SH) and Mo and Fe salts to form NHj and NjH in low yield . In similar systems, nitriles and isonitriles are reduced to NHj and amines in low yield . 

The product ethylene is formed in a stoichiometric yield with the nitrile and isonitrile, and for methylallenimine, (C2H4) = 0.25 and deactivating mechanism is also operative. The overall mode of decomposition bears a close resemblance to that of the hydrocarbon analog, the methylenecyclopropane ring system. 

Allerhand, A. and Schleyer, P.V.R. (1963a). Nitriles and Isonitriles as Proton Acceptors in Hydrogen Bonding Correlation of Avqh with Acceptor Structure. J.Am.Chem.Soc., 85, 866-870. 

Adducts (6) and (7) from amides and chlorophosphoric acid aiyl esters or dichlorophosphoric acid aryl esters respectively are well known. - The adducts are formed in a 1 1 ratio. They have been applied to the synthesis of mixed anhydrides from diarylphosphoric acids and carboxylic acids, as well as mixed substituted esters of pyrophosphoric acid. The adduct formation between primary or secondary carboxamides and dichlorophosphates has been used to prepare nitriles and isonitriles respectively. The adduct from DMF and phenyldichlorophosphate is a useful reagent for the preparation of carboxylic acid esters from the corresponding acids and alcohols, 3-lactams from imines and carboxylic acids," carboxylic acid anhydrides, carboxylic acid esters and thiol esters. Adducts of amides with ester amides or diamides of chlorophosphoric acid have been studied. ... 

No coupling is observed between CH3 and N in acetonitrile (CH3—C = N), but there is a coupling in the corresponding isonitrile (CH3 — N = C). Explain. This is not a distance effect. The phenomenon is general for nitriles and isonitriles. 

Values of /(C-N) across the triple bond in nitriles and isonitriles are negative. (106, 109) In both acetonitrile and methylisocyanide the Fermi contact contribution to /(N-C) is predicted to be positive and, for the methylisocyanide, quite large. The orbital and spin-dipolar mechanisms are predicted to make a negative contribution thus it appears that the latter two mechanisms are important for coupling across triple bonds. 

The data given in Table CVIII show a difference in the energies of the C==e=N bond in HGN, nitriles and isonitriles. In the nitrile group, bond resonance occurs between the homopolar structures —G and the ionic... 

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