Carbanions trityl

Pyrroline-A-oxide (258) is isomerized into y-lactam (259) in the presence of lithium diisopropylamine (LDA) (470) and sodium trityl (471). In these reactions, deprotonation at C3 occurs, leading to carbanion (260). Then oxygen migration from Ni to C2 takes place via intermediate formation of oxaziridine... 

The method was used in studies of a fungal heterogalactan.150 The polysaccharide was subjected to successive tritylation, methylation, detritylation, p-toluenesulfonylation, reaction with sodium iodide, and, finally, reaction with sodium p-toluenesulfinate. The product was then treated with sodium methylsulfinyl carbanion in dimethyl sulfoxide, the product remethylated, and the polysaccharide material recovered by gel chromatography. The polymer was hydrolyzed, and the sugars in the hydrolyzate were analyzed, as the alditol acetates, by g.l.c.-m.s.1 The analysis revealed that —60% of the hexose residues that were unsubstituted at C-6 had been eliminated. As the product was still polymeric, it was concluded that these residues had constituted a part of side chains linked to a main chain of (1 — 6)-linked D-galactose residues. 

Advantage has been taken of the ready accessibility of eleven para-substituted trityl and 9-phenylxanthyl cations, radicals, and carbanions in a study of the quantitative relationship between their stabilities under similar conditions.2 Hammett-type correlations have also been demonstrated for each series. Heats and free energies of deprotonation and the first and second oxidation potentials of the resulting carbanions were compared. The first and second reduction potentials and the p/CR values of the cations in aqueous sulfuric acid were compared, as were calorimetric heats of hydride transfer from cyanoborohydride ion. For radicals, consistent results were obtained for bond dissociation energies derived, alternatively, from the carbocation and its reduction potential or from the carbanion and its oxidation potential. 

Triphenylmethanol, prepared in the experiment in Chapter 31, has played an interesting part in the history of organic chemistry. It was converted to the first stable carbocation and the first stable free radical. In this experiment triphenylmethanol is easily converted to the triphenylmethyl (trityl) carbocation, carbanion, and radical. Each of these is stabilized by ten contributing resonance forms and consequently is unusually stable. Because of their long conjugated systems, these forms absorb radiation in the visible region of the spectrum and thus can be detected visually. 

The triphenylmethyl carbanion, the trityl anion, can be generated by the reaction of triphenylmethane with the very powerful base, n-butyllithium. The reaction generates the blood-red lithium triphenylmethide and butane. The triphenylmethyl anion reacts much as a Grignard reagent does. In the present experiment it reacts with carbon dioxide to give triphenylacetic acid after acidification. Avoid an excess of n-butyllithium on reaction with carbon dioxide, it gives the vile-smelling pentanoic acid. 

In another paper Abraham provided a thermodynamic analysis that placed f-Bu Cl and the separated ions at about the same free energy, 14.5 kcal/mol above the reactant. This implies a AG of about 5 kcal/mol for collapse of the contact ion pair back to reactants, although the uncertainties in Abraham s analysis are at least 5 kcal/mol. Few related data are available, except some dynamic NMR results for the collapse of trityl and tropylium chloride ion pairs. " In both the NMR work and Abraham s analysis, solvent-separated ion pairs are not included as distinct entities. However, the interconversion of contact and solvent-separated ion pairs has been observed in ultraviolet studies of delocalized carbanions in THF. ... 

A master equation has been derived from both the pA R of trimethyl- and triphenylcyclo-propenylium ions, as well as of the trityl cation, and the pA of conjugate acids of various carbanions, so that the heat of reaction can be predicted for the covalent bond formation between carbocations and carbanions. ... 

As already shown by many of the above examples, physical methods, especially spectroscopic ones, are having a very strong impact on the development of physical organic chemistry, and it is only for lack of space that such important techniques as laser flash spectroscopy can only be mentioned here in passing. Having established itself as a highly efficient method for the study of carbenes and carbocations [63] laser flash spectroscopy has also been used to generate carbanions like the trityl anion recently, [64] and promises to become a useful method for the determination of carbanion reactivity as well. 

Electron-withdrawing substituents in anionic polymerizations enhance electron density at the double bonds or stabilize the carbanions by resonance. Anionic copolymerizations in many respects behave similarly to the cationic ones. For some comonomer pairs steric effects give rise to a tendency to altemate. The reactivities of the monomers in copolymerizations and the compositions of the resultant copolymers are subject to solvent polarity and to the effects of the counterions. The two, just as in cationic polymerizations, cannot be considered independently from each other. This, again, is due to the tightness of the ion pairs and to the amount of solvation. Furthermore, only monomers that possess similar polarity can be copolymerized by an anionic mechanism. Thus, for instance, styrene derivatives copolymerize with each other. Styrene, however, is unable to add to a methyl methacrylate anion, though it copolymerizes with butadiene and isoprene. In copolymerizations initiated by w-butyllithium in toluene and in tetrahydrofuran at-78 °C, the following order of reactivity with methyl methacrylate anions was observed. In toluene the order is diphenylmethyl methacrylate > benzyl methacrylate > methyl methacrylate > ethyl methacrylate > a-methylbenzyl methacrylate > isopropyl methacrylate > t-butyl methacrylate > trityl methacrylate > a,a -dimethyl-benzyl methacrylate. In tetrahydrofuran the order changes to trityl methacrylate > benzyl methacrylate > methyl methacrylate > diphenylmethyl methacrylate > ethyl methacrylate > a-methylbenzyl methacrylate > isopropyl methacrylate > a,a -dimethylbenzyl methacrylate > t-butyl methacrylate. 

MeO , OH , or EtO and methyl fluoride, anisole, and 4-fluoroanisole on the gas-phase 5 2 reactions between dimethylmethylphosphonate and methylformate and HOO versus HO , MeO , or EtO in an attempt to discover the origin of the O -effect on the Sf 2 reaction of carbanions with 4-substituted benzyl chlorides in liquid ammonia " on the solvolysis reaction and the 2 reaction between phenoxide ions, and both neutral and negatively charged amines and 4-substituted benzyl chlorides in liquid ammonia on the ionization rates (the step) of the 5" 1 reactions of many substituted trityl halides and carboxylates in aqueous acetone and in aqueous and pure acetonitrile in the presence of piperidine on the ionization rates ( i) of the 5 reactions of various diarylmethyl chlorides in the presence of piperidine, pyridine, or PPh3 in several dipolar aprotic solvents on the solvolyses of X,Y-substituted benzhydryl acetates in various aqueous MeOH and EtOH solutions and on the dispersions observed in Grunwald-Winstein correlations of 5 solvolyses of substrates with substituents containing adjacent tt-electrons. ... 

NaH stirred ca. 45 min. at 65-70° under Ng in excess dimethyl sulfoxide until Hg-evolution is complete, allowed to react with 1 equivalent of ethyl triphenyl-phosphonium bromide, then with 0.85 equivalent of benzophenone 1,1-di-phenyl-l-propene. Y 97.5%.—The reactivity of the methylsulfinyl carbanion (formed by reaction of NaH with dimethyl sulfoxide), which is even more basic than the trityl anion, is sufficient to convert phosphonium salts into ylides thereby permitting a simple and convenient modification of the Wittig reaction. E. J. Gorey and M. Ghaykowsky, Am. Soc. 8A, 866 (1962) / -diketones from carboxylic acid esters and ketones (s. Synth. Meth. 6, 737), sym. ) -diketones, s. J. J. Bloomfield, J. Org. Chem. 27, 2742 (1962). 

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