Metal phenyls reactions with

This copper-catalysed phenylation reaction with triphenylbismuth diacetate is not limited to glycols as it has been extended to the arylation of other hydroxylic substrates such as phenols and enols.27 Variously substituted phenolic substrates have been selectively 0-phenylated under very mild neutral conditions (1 to 24 hours at room temperature in methylene dichloiide). The best yields were obtained with metallic copper used as the catalyst. The electronic nature of the substituents of the phenol did not influence the yields (4-nitro, 97% 3,5-dimethoxy, 90%). Only steric hindrance of the 2- and 6-substituents interfered with the reactivity. Thus only 26% of the 0-phenyl ether was obtained in the phenylation of 2,4-di-rerr-butylphenol, and no phenylation took place in the case of 2,4,6-tri-rer/-... 

The presence of a tnalkylsUyl group in a fluonnated organic compound may be useful to direct further transformations of that matenal Yet m some instances it IS the fluonnated substituent that controls the reactions of the tnalkylsdyl group Contrary to predictions, treatment of tert-hnlyX 3-tnfluoromethyl-6-tnmethylsilyl-phenyl carbamate with rert-butyllithium results m metallation of one of the methyl groups attached to silicon rather than that of the aromatic nng [90] (equation 75)... 

Coming back to the mechanism of dediazoniation, mechnism B in Scheme 9-2 is consistent with all experimental data known in 1973. Mechanism B was, indeed, mentioned in that paper (Zollinger, 1973 a) as an explanation, but not proposed as the explanation because it violated the common knowledge mentioned above. If that reverse reaction of the phenyl cation is faster than the forward reaction with water or metal halides, the rate is dependent on the concentrations of compounds involved only in the second step of the mechanism, even if that step is much faster than the first (forward) step. 

Durst and coworkers were the first to report the condensation of chiral a-sulphinyl carbanions with carbonyl compounds477. They found that metallation of ( + )-(S)-benzyl methyl sulphoxide 397 followed by quenching with acetone gives a mixture of dia-stereoisomeric /i-hydroxy sulphoxides 398 in a 15 1 ratio (equation 233). The synthesis of optically active oxiranes was based on this reaction (equation 234). In this context, it is interesting to point out that condensation of benzyl phenyl sulphoxide with benzaldehyde gave a mixture of four / -sulphinyl alcohols (40% overall yield), the ratio of which after immediate work-up was 41 19 8 32478. 

Kitatani et al. found that tungsten(VI) chloride would catalyse the formation of a range of oxazoles from benzoyl(phenyl)diazomethane and nitriles (Scheme 17).<74TL1531, 77BCJ1647> The reaction with acetonitrile was studied with a range of other metal chlorides, but all proved less satisfactory than WCle. They attributed the catalytic nature of tungsten(Vl) chloride to both its Lewis acidity and the affinity of tungsten for carbenes. 

Muller et al. have also examined the enantioselectivity and the stereochemical course of copper-catalyzed intramolecular CH insertions of phenyl-iodonium ylides [34]. The decomposition of diazo compounds in the presence of transition metals leads to typical reactions for metal-carbenoid intermediates, such as cyclopropanations, insertions into X - H bonds, and formation of ylides with heteroatoms that have available lone pairs. Since diazo compounds are potentially explosive, toxic, and carcinogenic, the number of industrial applications is limited. Phenyliodonium ylides are potential substitutes for diazo compounds in metal-carbenoid reactions. Their photochemical, thermal, and transition-metal-catalyzed decompositions exhibit some similarities to those of diazo compounds. 

However, none of these compounds can be easily resolved except TM (16) Itself. Me prefer to resolve as early as possible, (page T 94), so It is better to carry out the Diels-Alder reaction with acrylic acid and resolve acid (19) before adding the phenyl group by a Grignard reaction. The benzylic alcohol group in (20) can be taken out by metal-anunonia reduction. Syrithesis ... 

The reactivities of hydrido(phenoxo) complexes of trons-[MH(OPh)L2] (6 M = Ni 7 M = Pt) (L = phosphine) were examined (Eqs. 6.29, 6.30 Scheme 6-16), and a high nucleophiUdty for the metal-bound phenoxide was suggested [9, 10]. Reaction with methyl iodide produced anisole and trans-[MH(I)L2] for both Ni and Pt complexes. Phenyl isocyanate also provided the insertion products into the metal-phenoxo... 

The tris(trimethylsilyl)silyl ligands can be easily modified by reactions with silyl chlorides, as shown with a series of phenylated species Mes Ph SiCl (n = 0-3). Furthermore, triisopropyl, thexyldimethylsilyl, or tert-butyldimethylsilyl substitution are all easily possible.190 The crystallographic characterization of some of the alkali metal derivatives indicates a direct correlation between ligand size and resulting structural parameters. 

Phenyl cyclopropenone is not capable of thermal dimerization. On treatment with Cu2+ ions, however, a well-defined tetramer is formed54, to which structure 265 of a polyene dilactone was assigned. Its generation can be rationalized via 264 with both the above dimerization types contributing in metal-catalyzed reactions. 

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