Alkali metal reaction with aromatics

These studies, which employed density functional theory (DFT) methods (B3LYP/LANL2DZ/Gaussian 98) proposed that the reactions of all alkali metal phenoxides with C02 followed a similar ground mechanism that comprised three intermediates and three transition states. In step 1, C02 must first be activated by an alkali metal phenoxide. In the case of the sodium phenoxide [24a], C02 can only attack at the polarized O-Na bond to form a Ph0Na/C02 complex as the first intermediate (structure 4). The calculation definitely rules out a direct C-C bond formation at the aromatic ring. 

Either fusion with alkali metals or reaction with aUcali-metal complexes with aromatic hydrocarbons will break down most fluorocarbon systems, due to the high electron affinities of these systems. Such reactions form the basis of some methods of elemental analysis [13], the fluorine being estimated as hydrogen fluoride after ion exchange. Surface defluorination of PTFE occurs with alkali metals and using other techniques [14]. Per-fluorocycloalkanes give aromatic compounds by passage over hot iron and this provides a potential route to a variety of perfluoroaromatic systems (Chapter 9, Section IB). 

Secondary aromatic phosphines can be prepared from tertiary phosphines by cleavage with sodium in liquid ammonia, and the detailed preparation of diphenylphosphine by this method has been reported. Diphenylphosphine has also been prepared by the reaction of chlorodiphenylphosphine with alkali metals or with lithium tetrahydroaluminate. This phosphine has been also obtained from diphenyltrichlorophosphorane or tetraphenyldiphosphine-disulfide with lithium aluminum hydride. A faster and easier method of preparation, which gives equally high yields, consists in the cleavage of tri-phenylphosphine with lithium metal in tetrahydrofuran, followed by hydrolysis of lithium diphenylphosphide with water to generate the phosphine. ... 

Information on the initiation reaction is restricted to the solvent tetrahydrofuran, in conjunction with the monomers a-methylstyrene and 1,1,-diphenylethylene which can only form oligomers, at least at room temperature. Initiation may once again be produced by metal alkyls or aryls, by direct contact of the olefin with an alkali metal film, or by use of the addition products of alkali metals to condensed aromatic ring compounds. 

The recent application of sonochemistry to the reaction of aroyl chlorides with KCN in acetonitrile is very interesting. Aromatic acyl cyanides could also be prepared by reaction of aroyl chlorides with KCN impregnated onto XAD resins. A number of patents describe the results of the two-phase interactions of alkali metal cyanides with a solution of acyl halides or anhydrides in aprotic organic solvents, which in general run in the presence of Cu salts. ... 

Polycyclic aromatic compounds can react with alkali metals in ether solution to produce monomeric radical ions [Ij. The reaction involves the transfer of an electron from the alkali metal to the aromatic compound. For sodium and naphthalene, for example. 

The radical nature of the anion radical (X) has been established from electron spin resonance spectroscopy and the carbanion nature by its reaction with carbon dioxide to form the carboxylic acid derivative. The equilibrium in Eq. (8.13) depends on the electron affinity of the aromatic hydrocarbon and the donor properties of the solvent. Tetrahydrofuran (THF) is a useful solvent for such reactions. This fairly polar solvent (dielectric constant = 7.6 at room temperature) promotes transfer of the s electron from the alkali metal to the aromatic compound and stabilization of the resultant complex, primarily via solvation of the cation. Sodium naphthalenide is... 

Addition of I-alkynes to carbonyls. Alkali metal acetylides are usually used for this addition, but their strong basic properties can cause problems with base-sensitive substrates. 1-Alkynes can add directly if the reaction is carried out in combination with Sn(OTf)2 and a base (1 1). In reactions with aromatic alkyncs, DBU is the preferred base, but l,8-bis(dimethylamino)naphthalne is preferred for reactions with aliphatic alkyncs. Silylation of 1-alkyncs with R,SiCl can also be promoted by Sn(OTf)2 and an amine. 

In contrast to PTK materials, the addition of sulfone groups to the polymer minimize the problems. When a 4,4 -dihalobenzophenone as a di-halogenated aromatic compound is combined with a 4,4 -dihalodiphenyl sulfone followed by their reaction with an alkali metal sulfide, an aromatic thioether ketone/thioether sulfone random copolymer can be obtained with a high molecular weight. 

Aresta M, Dibenedetto A, Quaranta E (1995) Reaction of alkali-metal tetraphenylborates with amines in the presence of CO2 a new easy way to aliphatic and aromatic alkali-metal carbamates. J Chem Soc Dalton Trans 3359-3363... 

Neta.1 Ama.lga.ms. Alkali metal amalgams function in a manner similar to a mercury cathode in an electrochemical reaction (63). However, it is more difficult to control the reducing power of an amalgam. In the reduction of nitro compounds with an NH4(Hg) amalgam, a variety of products are possible. Aliphatic nitro compounds are reduced to the hydroxylamines, whereas aromatic nitro compounds can give amino, hydra2o, a2o, or a2oxy compounds. 

Base catalysis is most effective with alkali metals dispersed on solid supports or, in the homogeneous form, as aldoxides, amides, and so on. Small amounts of promoters form organoalkali comnpounds that really contribute the catalytic power. Basic ion exchange resins also are usebil. Base-catalyzed processes include isomerization and oligomerization of olefins, reactions of olefins with aromatics, and hydrogenation of polynuclear aromatics. 

A similar distribution of copper reagents can be obtained via the du ect reaction of copper metal with dibromodifluoromethane or bromochlorodifluoromethane in DMF at 85-95 °C [2J2] The oligomerization can be supressed via the addition of alkali metal fluorides to the reaction mixture [272] When HMPAis added to the trifluoromethylcopper solution, decomposition is slowed, and this solution can be used to trifluoromethylate aromatic iodides [270] (equation 143). 

Solutions of alkali metals in liquid ammonia have been developed as versatile reducing agents which effect reactions with organic compounds that are otherwise difficult or impossible/ Aromatic systems are reduced smoothly to cyclic mono- or di-olefins and alkynes are reduced stereospecifically to frani-alkenes (in contrast to Pd/H2 which gives cA-alkenes). 

Electron transfer reactions involving alkali metals are heterogeneous, and for many purposes it is desirable to deal with a homogeneous electron transfer system. It was noticed by Scott39 that sodium and other alkali metals react rapidly with aromatic hydrocarbons like diphenyl, naphthalene, anthracene, etc., giving intensely colored complexes of a 1 to 1 ratio of sodium to hydro-... 

Reactions involving organic substances have some special features. Many of these substances are poorly soluble in aqueous solutions. Sometimes their solubilities can be raised by adding to the solution the salts of aromatic sulfonic acids with cations of the type [NHJ or alkali metal ions. These salts have a salting-in effect on poorly soluble organic substances. In many cases solutions in mixed or nonaque-ous solvents (e.g., methanol) are used. Suspensions of the organic substances in aqueous solutions are also useful for electrosynthesis. 

The sonochemistry of the other alkali metals is less explored. The use of ultrasound to produce colloidal Na has early origins and was found to greatly facilitate the production of the radical anion salt of 5,6-benzo-quinoline (225) and to give higher yields with greater control in the synthesis of phenylsodium (226). In addition, the use of an ultrasonic cleaning bath to promote the formation of other aromatic radical anions from chunk Na in undried solvents has been reported (227). Luche has recently studied the ultrasonic dispersion of potassium in toluene or xylene and its use for the cyclization of a, o-difunctionalized alkanes and for other reactions (228). 

Another example of the remarkable reactivity of Mg actuated by our procedure is its reaction with nitriles. In this respect, the Mg resembles an alkali metal more than an alkaline earth. Benzonitrile reacts with Mg overnight, in refluxing DME, to give 2,4,6-triphenyl-l,3,5-triazine and 2,4,5-triphenylimidazole in 26 and 27% yield, respectively, based on magnesium. Jhe imidazole was shown to arise, at least in part, from the action of Mg on the triazine. The trimerization of aromatic nitriles to give symmetrical triazines is not unknown, but generally the reactions are... 

Some of the investigations carried out in the first half of the twentieth century were related to CL associated with thermal decomposition of aromatic cyclic peroxides [75, 76] and the extremely low-level ultraviolet emission produced in different reaction systems such as neutralization and redox reactions involving oxidants (permanganate, halogens, and chromic acid in combination with oxalates, glucose, or bisulfite) [77], In this period some papers appeared in which the bright luminescence emitted when alkali metals were exposed to oxygen was reported. The phenomenon was described for derivatives of zinc [78], boron [79], and sodium, potassium, and aluminum [80]. 

Under the same conditions (batch or GL-PTC) discussed for CHg-acidic compounds, primary aromatic amines also react with DMC. In this case, although the reaction yields selectively the mono-A-methylated amines with no dimethylated by-products, sizable amounts of methyl carbamates (ArNHCOgMe) are formed. ° Much better results can be gathered in the presence of zeolites, particularly alkali metal exchanged Y and X faujasites. These aluminosilicates posses pseudospheri-cal cavities (supercavities) of 11-8 A in diameter, which can be accessed through channels whose size is 7.4 kP ... 

Then, contrary to our previous hypothesis, the reaction proceeds via a Bai2 displacement of aniline on DMC. The product, mono-A -methyl aniline (PhNHMe), plausibly adsorbs into the zeohte in a different way with respect to anihne, because different H-bonds (N H — O-zeolite) take place with the solid. As recently reported by Su et al., A-methyl amines also may interact with NaY by H-bonding between the protons of the methyl group and the oxygen atoms of the zeolite this probably forces the molecule a bit far from the catalytic surface in a fashion less apt to meet DMC and react with it. This behavior can account for the mono-A-methyl selectivity observed, which is specific to the use of DMC in the presence of alkali metal exchanged faujasites in fact, the bis-A-methylation of primary aromatic amines occurs easily with conventional methylating agents (i.e., dimethyl sulfate). ... 

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