Nitriles 2 molecules

A -azirines, 2-amina- 31, 667 (a,0-ethylenesulfonyl)-amidines 31,328 nitriles (2 molecules) 31, 611... 

In the Thorpe reaction, the a carbon of one nitrile molecule is added to the CN carbon of another, so this reaction is analogous to the aldol reaction (16-38). The C=NH bond is, of course, hydrolyzable (16-2), so p-keto nitriles can be prepared in this manner. The Thorpe reaction can be done intramolecularly, in which case it is... 

Combining the results of the spectroscopic and kinetic experiments allows us to partially confirm one aspect of the mechanism for CO oxidation. The IRRAS results showed that the nitrile molecules are able to disrupt the continuity of the CO adlayer at the molecular scale by blocking a fraction of the surface Pt atoms. This is in contrast to the procedure of preparing a partial CO adlayer by controlling the exposure to bulk solution, which produces a uniformly distributed CO layer without blocking Pt atoms by a second adsorbate (12). The fact that there is no evidence for enhanced CO oxidation kinetics in the solutions with added nitriles indicates that the presence of an exposed Pt atom next to the... 

The results in Figure 3 can now be interpreted. The nitrile molecules are able to compete with CO for Ft adsorption sites. 

Under the present conditions, we propose that the -CN group in the nitrile molecules acts in a similar fashion. The nitrile molecules are adsorbed on a fraction of the Pt surface atoms, and their presence forces the co-adsorbed CO molecules on the remaining sites to assume the bridging configuration. When the potential is increased, part of the driving force for this conversion is removed and the CO molecules convert back to their linear configuration. This conversion is irreversible when the potential is lowered a second time. The reason for this irreversibility is uncertain and should be explored further. 

A domino reaction of 1,1-diphenyl-3,3-dilithioallene (157) with benzonitrile yields both a yellow imidazole (158 R = Ph X = NH) (12%) and a colourless 5-imidazol-5-yl-l,4-dihydropyrimidine (159 R = Ph) (51%), the products, respectively, of the incorporation of three and four nitrile molecules. The proposed mechanism (Scheme 13) involves initial formation of an intermediate (160) that is the product of the interaction of three molecules of benzonitrile with l,l-diphenyl-3,3-dilithioallene (157), which cyclizes to (162 R = Ph) and then eliminates a molecule of benzonitrile to produce (161 R = Ph). Re-addition of benzonitrile at a different locus produces... 

The reaction depicted in equation 43 between a nitrile and a lithium amide takes place as a 1,2-addition to the cyano group. The product crystallizes as a dimer (236) in which the lithium atoms are solvated by nitrile molecules and differently bonded to the amidine moieties, as shown by XRD analysis. Low-temperature H NMR spectrum in solution points to uniform chemical environments for both the aryl groups and for the Me—Si groups, and to rapid rearrangement of the Li—N coordination structures. Acidolysis of the dimer in solution yields the corresponding amidine (237) . The crystal structure of the THF-solvated analog of 236 shows dissimilar N—Li bond lengths for the two Li atoms... 

The seven-membered metallacycles 89 (formed by ketone addition to [(butadiene)ZrCp2] cleanly add a nitrile molecule at elevated temperatures to yield the respective nine-membered metallacyclic products 96. Their hydrolysis then yields the 6-hydroxy-substituted non-conjugated unsaturated imines 97 under kinetic control. Within a few hours at room temperature these rearrange to the thermodynamically favored primary dienamine products 98.107 In this case the thermochemical diene conjugational energy makes the primary dienamines more stable than their conjugated imine tautomers (Scheme 32). 

Quinazoline derivatives may also be obtained by heating complex diazonium salts with nitriles45 under these conditions the nitrilium salt (49) first formed accepts a second nitrile molecule and the resulting product is cyclized by electrophilic attack on the ortho position of the... 

Ferrini and Marxer65 have recently shown that vinylene carbonate reacts with primary amides, in the presence of polyphosphoric acid, to yield 2-substituted oxazole derivatives. Yields are low (2-34%), and phenoxy- and phenyl-acetamide, p-methylbenzamide, and salicylamide do not give oxazole derivatives. Although the reaction has been interpreted according to Scheme 3, the nucleophilic attack of a nitrile molecule (from the amide dehydration), with a nitrilium salt as intermediate (Scheme 4), cannot be excluded.06... 

This section focuses on the modification of epoxy resins by blending with acrylonitrile butadiene (nitrile) resins. These are true alloyed blends since the nitrile rubber usually contains no groups that are normally reactive with epoxy groups. The nitrile molecules and the epoxy molecules intermingle as a blend to provide a single-phase alloy. If a large elastomer concentration is used, no phase separation will occur to form precipitates. 

In the latter reaction (equation 53) an initial [2 + 2] cycloaddition to form 1,3-heterodiene 161 via 160 is assumed. It is then followed by a [4 + 2] cycloaddition to another nitrile molecule, giving 162101. 

If the rearrangement of the chlorocarbenium intermediate is impossible, then the latter (e.g. 249) adds in consecutive order two nitrile molecules to form the pyrimidine 25386 (equation 70). 

Diels-Alder reactions of oxazoles have proven to be quite versatile and continue to attract attention. Oxazoles have traditionally been used as the diene component and react with alkyne dienophiles to give furan products after extrusion of a nitrile molecule via a reverse-cycloaddition process. This method has been used to access highly substituted furans and has been utilized in numerous natural product syntheses. The reaction typically requires the use of high temperatures for efficient conversion. The furan intermediate 67 was obtained by a thermal intermole-cular Diels-Alder reaction between oxazole 66 and an acetylene. Furan 67 was a key intermediate for the synthesis of (—)-teubrevin G (Scheme 10) <2000JA9324>. Similarly, furan 68, obtained from a Diels-Alder reaction between 4-phenyloxazole and an acetylene, served as an intermediate in the total synthesis of the natural product cornexistin (Scheme 10) <20030L89>. 

The application of this reaction to an aza analog leads to an azacyclobutadiene 138). This compound is cleaved to two 1-alkyne and two nitrile molecules which suggests that an equilibrium exists between the two azacyclobutadiene structures (129). This reaction is widely used for the synthesis of cyclobutadiene intermediates. 

The cyclotrimerization of nitriles (R—CN) is a very common route to 1,3,5-triazi-nes.10-12,119-121 The reaction conditions and catalysts are dependent on the R part of the nitrile molecule several reaction mechanisms are involved in the trimerization reaction. Aliphatic and aromatic nitriles can trimerize upon application of high pressure and/or heat however, catalysts are used more frequently, e.g. hydrogen chloride, ehlorosulfonic acid, boron trifluoride, sodium metal, Grignard reagents and sodium triphenylmethanide. The same also applies to all other nitriles (a-atom not carbon). 

Alkyl cyanides with electron-withdrawing substituents (e.g., halogen atoms) are more reactive and cyclotrimerize under acidic and basic conditions, as well as at high pressure. In the presence of hydrogen chloride, the formation of an intermediate adduct of two nitrile molecules, which cyclizes upon the addition of a third nitrile, has been suggested145 (cf. Houben-Weyl, Vol. E5,... 

In this respect, both free nitrile molecules and their complex salts with acidic catalysts can take part in the formation of the triazinc.146 Hydrogen chloride, sulfuric acid, Lewis acids and complexes of Lewis acids and hydrogen halides are generally used as catalysts the complexes usually have the best catalytic potential.147-150... 

Uncatalyzed, the trimerization proceeds very slowly. Effective catalysts are Bronstedt and Lewis acids, or a combination of both (Norton s catalyst).145,147,268 The hydrogen chloride catalyzed reaction forms a diene , e.g. 26, in the first step, which adds a further dienophilic nitrile molecule to provide a complex which loses hydrogen chloride to give the mixed trimer.145... 

Retrosynthetic analysis reduces the 1,3,5-triazine system by cycloreversion to three HCN or nitrile molecules. Alternatively, bond fission at the C=N units suggests amides and their... 

Scheme 1.13. Oxidative coupling of alkyne and nitrile molecules to produce benzene and pyridine...

K, and using the van t Hoff s equation, the enthalpy of complex formation was calculated to be -AH = 16.7 4.3 kJ/mol. It was found, moreover, that the absorption intensity in ultraviolet at wavenumber of v = 35 000 cm is the greatest at equimolar concentration of the substances tested. Therefore in the complex one n-butyro-nitrile molecule corresponds to one n-dodecene-1 molecule (Fig. 13). 

---