Sodium, reaction with arenes

Fluoroalkjiations are frequentiy performed indirectly using tandem reactions. Arenes react with sodium borohydride in trifluoroacetic acid to afford otherwise difficult to obtain l,l,l-trifluoro-2,2-diarylethanes. Presumably sodium borohydride reacts initially with the trifluoroacetic acid to produce the trifluoroacetaldehyde or its equivalent, which rapidly undergoes Friedel-Crafts-type condensation to give an intermediate carbinol. The carbinol further alkylates ben2ene under the reaction conditions giving the observed product. The reaction with stericaHy crowded arenes such as mesitylene and durene... 

The hemidecarboxylation of sodium phthaiate on reaction with mercuric acetate in boiling water [Eq. (82), X = H] (90) was the first reported thermal decarboxylation. The reaction has been observed for a number of arenes with two adjacent carboxylate groups (1-4,91) and has been named the Pesci reaction (91). Studies of 3-substituted sodium phthalates or of preformed mercuric 3-substituted phthalates have shown that the sterically hindered carboxyl group (the 2-carboxyl) is preferentially eliminated whether X is electron-donating or electron-withdrawing [Eq. (82), X = Me (91), Cl, N02 (91,93), Br (93), or C02H (94)]. A similar conclusion was drawn from the decomposition of mercuric 1,2-naph-thalenedicarboxylate and 3,4-phenanthrenedicarboxylate (91). 

As hosts for cations, the phenolic oxygen atoms at the calixarene lower rim (Figure 3.81) have the potential to act in a similar way to the anisole residues of the spherands, either in the original hydroxyl form or as alkyl ether derivatives. This kind of behaviour has been observed for the methyl ether of the parent /j-f-butylcalix[4] arene (compound 3.121) upon reaction with a mixture of sodium benzoate, one... 

Benzene cyclopentadienyl ruthenium(II) complex 125 undergoes nucleophilic addition at the arene ligand via the addition of sodium borohy-dride or phenyllithium. Reaction with phenyllithium gives the exo-phenyl cyclohexadienyl derivative 249 in 89% yield (154) [Eq. (32)]. 

More recently, cationic intermediates have been observed in the Heck reactions of arene diazonium salts catalyzed by triolefinic macrocycle Pd(0) complexes [17,59], o-iodophenols and enoates to form new lactones [60], and o-iodophenols with olefins (the oxa-Heck reaction) [61 ]. In the first case ions were formed by oxidation of the analyte at the capillary, or by association of [NH4] or Na". In the two other cases ionization occurred through the more typical loss of a halide ligand. The oxa-Heck reaction provides a good example of how these experiments are typically performed and the type of information that can be obtained. The oxyarylations of olefins were performed in acetone, catalyzed by palladium, and required the presence of sodium carbonate as base. Samples from the reaction mixtures were diluted with acetonitrile and analyzed by ESI(+)-MS. Loss of iodide after oxidative addition of o-iodophenol to palladium afforded positively-charged intermediates. Species consistent with oxidative addition, such as [Pd(PPh3)2(C6H50)], and the formation of palladacycles of the type seen in Scheme 8 were observed. Based on this, a mechanism for the reaction was proposed (Scheme 8). 

Friedel-Crafts reaction of arenes with a-chloro-a-(methylthio)acetophenones [19], When A -phenylbenzimidoyl chlorides are aroylated with an aryl halide in the presence of a catalytic amount of an azoliuni salt (such as 1,3-dimethylimidazolium iodide) and sodium hydride, followed by acid treatment in TUF, unsymmetrical benzils can be isolated in 80-92% yields [201. Added to this method is the sequence ketone enaminoketone a-diketone, which cleaves a carbon-carbon double bond in the final stage by photooxygenation [21]. 

An interesting application of the Fujiwara-Moritani/oxidative Heck reaction for the synthesis of benzo furans was recently reported by the Stoltz lab [31]. A variety of allyl phenyl ethers (all containing electron-rich aryl components) react with 10 mol% palladium acetate, 20 mol% ethyl nicotinate, 20 mol% sodium acetate, and one equivalent of benzoquinone at 100°C to provide benzofurans in 52-79% yield (e.g. 16—>17). The mechanism of this transformation begins with arene palladation of Pd(II) followed by olefin insertion, p-hydrogen elimination, and olefin isomerization to the thermodynamically favored benzofuran product. The resulting Pd(0) species is then oxidized to Pd(ll) thus regenerating the active catalyst. 

Aryltrifluoromethyl ketones are prepared by reaction of an aryl-lithium with a,a,a-trifluoro-N,N-dimethylacetamide. 2-Acyloxypyridines and N-acylimidazoles, " in conjunction with trifluoroacetic acid, acylate arenes in good yield without the need for a classical Friedel-Crafts catalyst or a preformed mixed anhydride. However, imidazole in trifluoroacetic anhydride is reported to form 2-aryl-Af,JV -diacyl-4-imidazolines with arenes reactive towards electrophilic attack. These adducts are readily hydrolysed by sodium hydroxide to the corresponding aldehyde [equation (14)]. This sequence may offer advantages over the Vilsmeier method of formylation, in that the aldehyde is introduced in a protected form. 

Recently it was pointed out [6] that potassium and sodium bromate oxidize arenes in good yields in a 3 2 dioxane-water solution by using cerium ammonium nitrate (CAN) as catalyst. Toluene derivatives are oxidized to ca. 1 1 mixture of benzaldehydes and benzoic acids, while ethylbenzenes are converted to acetophenones. According to the proposed mechanistic scheme, water either influences the polarity of the reaction medium or acts as the reagent, reacting with the intermediate benzylic carbonium ion to give a hydroxy derivative, which is oxidized from either Ce or BrOa ions. 

Several amphiphilic ruthenium clusters that contain an oxovanadium [(7/ -p-MeC6H4Pr )4Ru4V60i9] 127 or oxomo-lybdenum [(r7 -p-MeC6H4Pr )4Ru4Mo60i6] 128 core were obtained from the reactions of arene ruthenium dichloride dimer with sodium vanadate or sodium molybdate (Table 10). The NMR spectroscopy and partial charge calculations indicated the presence of three different kinds of oxygen atoms in 128. A new Chevrel-type cluster that contains Ru and Nb has been reported. The synthesis of phases of composition Nb Ru6-xTes (2.83 < x < 3.50) was... 

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