Phenol-acetonitrile complex

5 kJmoC, and therefore has a binding energy E (PhOH-ACN) of 5.8 kJmoG.  

If the conventional strnctnre is formed dne to the typical medium-strength hydrogen 

referring to the hydrogen-bond bending motions and originating dne to the molecnlar dipole rotation, by analogy with the band at 90 cm in the phenol-pyridine complex . 

FIGURE 53. Complexes of phenol with acetonitrile. The bond lengths are in A. Values in parentheses correspond to the optimized geometries of the free phenol and acetonitrile molecules. Adapted from Reference 761 with permission 

TABLE 41. Some key features of the stable complexes of phenol with two acetonitrile  

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General and theoretical aspects of phenols TABLE 40. Some key features of 1 1 phenol-acetonitrile complexes... 

We have found the novel structure by which phenol complexes with the acetonitrile molecule. Such a structure has an absolutely different hydrogen bonding pattern, which certainly makes it less favourable on comparison with the conventional one attributed to the <7-type hydrogen bonding. A phenol-acetonitrile complex formation via tt hydrogen bonding between the OH group of phenol and the C=N bond should be ruled out affirmatively. 

However, we have shown that the novel bond formation between phenol and acetonitrile plays a role on increasing the concentration of the acetonitrile. By postulating its existence under conditions in which phenol interacts with two acetonitrile molecules, we were able to explain the experimental data that have seemed to be rather unclear during the last four decades. Moreover, we have predicted the existence of another structure formed from phenol and two molecules of acetonitrile, which is characterized by a significant downshift by 244 cm of the v(OH) stretching mode of phenol, never observed experimentally in phenol-acetonitrile complexes. We have suggested that it is likely to exist in the gas phase and non-polar solvents at lower temperatures and showed its fingerprints in order to facilitate its possible experimental detection. 

Structural analogues of the /]4-vinylketene E were isolated by Wulff, Rudler and Moser [15]. The enaminoketene complex 11 was obtained from an intramolecular reaction of the chromium pentacarbonyl carbene complex 10. The silyl vinylketene 13 was isolated from the reaction of the methoxy(phenyl)-carbene chromium complex 1 and a silyl-substituted phenylacetylene 12, and -in contrast to alkene carbene complex 7 - gave the benzannulation product 14 after heating to 165 °C in acetonitrile (Scheme 6). The last step of the benzannulation reaction is the tautomerisation of the /]4-cyclohexadienone F to afford the phenol product G. The existence of such an intermediate and its capacity to undergo a subsequent step was validated by Wulff, who synthesised an... 

The first indication that such O-coordinated (phenoxyl)metal complexes are stable and amenable to investigation by spectroscopy was obtained when the electrochemistry of the colorless, diamagnetic complexes [Mm(LBu2)], [Mm(LBuMet)] (M = Ga, Sc) containing three coordinated phenolates in the cis-position relative to each other was investigated in acetonitrile solutions (142). A representative structure of [Scm(LBuMet)] is shown in Fig. 12. 

Arene(alkoxy)carbene chromium complexes react with aryl-, alkyl-, terminal, or internal alkynes in ethers or acetonitrile to yield 4-alkoxy-1-naphthols, with the sterically more demanding substituent of the alkyne (Rl Figure 2.24) ortho to the hydroxy group. Acceptor-substituted alkynes can also be used in this reaction (Entry 4, Table 2.17) [331]. Donor-substituted alkynes can however lead to the formation of other products [191,192]. Also (diarylcarbene)pentacarbonyl chromium complexes can react with alkynes to yield phenols [332]. 

Electron donation by potential carcinogens, such as 2-acetylaminodi-benzothiophene, has been estimated from the strength of their charge-transfer complexes with chloranil in acetonitrile. - In this context it should be noted that the hydrogen bonding of phenol to the 77-electrons of dibenzothiophene has been studied and that a thiourea adduct has proved useful in the removal of dibenzothiophene from oil. - ... 

Another example is the separation of several sulfonamides in acetonitrile by adding silver ions. Compounds such as N-containing heterocyclics were found to build selective charge transfer complexes with Ag+, which improves the selectivity of the separation. Phenols, carboxylic acids, and alcohols interact with anions such as CIO, BE, NO, Cl t,SO , and Cl in acetonitrile as solvent. The resulting electrophoretic mobility of the weak Bronsted acids (HA) in the presence of such anions is the result of the formation of complexes of the type [X. .. HA] due to the formation of hydrogen bonds (13). 

Chiral (salen)Mn(III)Cl complexes are useful catalysts for the asymmetric epoxidation of isolated bonds. Jacobsen et al. used these catalysts for the asymmetric oxidation of aryl alkyl sulfides with unbuffered 30% hydrogen peroxide in acetonitrile [74]. The catalytic activity of these complexes was high (2-3 mol %), but the maximum enantioselectivity achieved was rather modest (68% ee for methyl o-bromophenyl sulfoxide). The chiral salen ligands used for the catalysts were based on 23 (Scheme 6C.9) bearing substituents at the ortho and meta positions of the phenol moiety. Because the structures of these ligands can easily be modified, substantia] improvements may well be made by changing the steric and electronic properties of the substituents. Katsuki et al. reported that cationic chiral (salen)Mn(III) complexes 24 and 25 were excellent catalysts (1 mol %) for the oxidation of sulfides with iodosylbenzene, which achieved excellent enantioselectivity [75,76]. The best result in this catalyst system was given by complex 24 in the formation of orthonitrophenyl methyl sulfoxide that was isolated in 94% yield and 94% ee [76]. 

However, if the phenol is first treated with the complex formed from triphenylphosphine and a halogen in acetonitrile solution, an aryloxytriphenylphosphonium halide is formed which on thermal decomposition yields the aryl halide in good yield (e.g. the preparation of p-bromochlorobenzene, Expt 6.30). 

In the previous reaction when the solvent was changed to acetonitrile-methanol, quinone monoacetals were formed. Both products were used for the synthesis of 5-oxygenated indoles [11], This type of transformation also occurred using DIB (Section 3.3) however, the use of BTI activated 4-alkyl phenols which reacted not only with methanol but also with other nucleophiles, simple ones such as water and fluoride, or more complex, according to the general scheme ... 

When the parent phenol complex of [Os] 85 is combined with MVK and pyridine in acetonitrile, a Michael addition occurs to give the 4H-phenol complex 86 in 91 % yield (Scheme 11). This complex is remarkably stable and resists rearomatization even when allowed to stand in an acidic solution of acetonitrile for 24 h. However, addition of an amine base induces rearomatization to yield complex 87. This complex may be heated to afford the deme-talated substitution product 88 (raspberry ketone) in 71 % yield (based on 85) [29]. 

Nitro-4-(trifluoromethyl)-phenol 42 (Scheme 17) in reaction with 2-bromo-2-methyl-propionamide in the presence of cesium carbonate and cesium iodide in acetonitrile afforded 2-hydroxy-2-methylpropionamide 43, apparently via derivative 44 as the intermediate [32]. Amide 44, prepared on a circuitous route, on reduction with borane-dimethylsulfide complex, gave amine 45 as the only isolated product. The parent 2-hydroxy-2-methyl-W-(2-... 

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