Phenyl exchange

Besides the perhaps trivial examples of isomers, such as the regiospedfic thiophene, pyridine, and phenyl exchanges, the nine remaining isosteric replacements include mostly nonclassical ones, that is, substituents that are structurally distinct, exhibiting different steric electronic properties [6]. 

Morita, D.K., Stille, J.K. and Norton, J.R. (1995) Methyl/phenyl exchange between palladium and a phosphine ligand. Consequences for catalytic coupling reactions. J. Am. Chem. Soc., 117, 8576-81. 

Organic compounds M—R and hydrides M—H of main group metals such as Mg, Zn, B, Al, Sn, SI, and Hg react with A—Pd—X complexes formed by oxidative addition, and an organic group or hydride is transferred to Pd by exchange reaction of X with R or H. In other words, the alkylation of Pd takes place (eq. 9). A driving force of the reaction, which is called transmetallation, is ascribed to the difference in the electronegativities of two metals. A typical example is the phenylation of phenylpalladium iodide with phenyltributyltin to form diphenylpalladium (16). 

Lena (9) has used this method to prepare the 2-phenyl-4-methylselenazole and the 2,4-dimethylselenazole. An optimization of the experimental conditions in the O-Se exchange must be necessary. 

Each act of proton abstraction from the a carbon converts a chiral molecule to an achi ral enol or enolate ion The sp hybridized carbon that is the chirality center m the start mg ketone becomes sp hybridized m the enol or enolate Careful kinetic studies have established that the rate of loss of optical activity of sec butyl phenyl ketone is equal to Its rate of hydrogen-deuterium exchange its rate of brommation and its rate of lodma tion In each case the rate determining step is conversion of the starting ketone to the enol or enolate anion... 

The search for a system with less decomposition and a higher separation factor has been summarized (27—29). The most promising system is the BE —anisole system, in which BE (g) exchanges with the anisole [100-66-3] (methyl phenyl ether) -BF3 complex (1) (30) ... 

By changing the substituents on the ethylenic linkage and exchanging phenyl rings for heteroaromatic rings, photochromic systems that are thermally reversible are transformed into systems that are thermally irreversible but photochemically reversible. The transition between the ben2othiophene-derivative... 

Table 2 summarizes some of the transformations of substituents which have been carried out on azetidines without effect on the ring <79CRV33l). Other transformations of interest are the base catalyzed epimerization, H exchange and alkylation of the activated H-3 in azetidines (26) (69JHC153) and the nitration, reduction, diazotization and hence further modification of the aromatic ring in 3-phenyl-fV-acetylazetidine (27) (61LA 647)83). 

Tetrazole, 5-phenoxy-l -phenyl-mass spectra, 5, 801 photolysis, 5, 811 Tetrazole, 1-phenyl-deuterium-hydrogen exchange, 5, 806 mercuration, 5, 59 NMR, 5, 798 tautomerism, 5, 804 UV spectra, 5, 798 Tetrazole, 2-phenyl-NMR, 5, 798 tautomerism, 5, 804 UV spectra, 5, 798 Tetrazole, 5-phenyl-alkylation, 5, 818 anti-inflammatory activity, 5, 835 blowing agent, 1, 410 reactions... 

Tetrazolium iodide, l,3-dialkyl-5-phenyl-synthesis, 5, 815 Tetrazolium salts electrochemical reduction, 5, 73 hydrogen exchange, 5, 70 Tetrazolium salts, 2,3-diphenyl-5-oxide... 

In the 1960s the Carborundum company introduced the polymer Ekonol P-3000. This was the polymer of p-hydroxybenzoic acid (I) Figure 25.22), in practice produced by the self-ester exchange of its phenyl ester to prevent decarboxylation. A blend with PTFE, Ekonol T-4000, was also produced. 

Vinyl and phenyl mfluoromethyl groups are reactive in the presence of aluminum chloride [10] Replacement of fluorine by chlorine often occurs Polyfluori-nated trifluoromethylbenzenes form reactive a,a-difluorobenzyl cations in antimony pentafluoride [11] 1 Phenylperfluoropropene cyclizes in aluminum chloride to afford 1,1,3-trichloro 2 fluoroindene [10] (equation 10) The reaction IS hypothesized to proceed via an allylic carbocation, whose fluoride atoms undergo halogen exchange... 

An extension ot this reaction provides a number of other perfluorovinylic halides [54] The type of reaction products from the thermal decomposition reaction and the type of hydrocarbon Grignard reagent used in the exchange reaction are solvent-dependent When an excess ot phenylmagnesium bromide is used, a variety of phenylated products are formed depending on the excess amount used [4S (equation 23)... 

Propanediol, acetone. This method removes the boronate by exchange. 2-Methylpentane-2,5-diol in acetic acid cleaves a phenyl boronate (85% yield). 

Eda and Kurth applied a similar solid-phase combinatorial strategy for synthesis of pyridinium, tetrahydropyridine, and piperidine frameworks as potential inhibitors of vesicular acetylcholine transporter. One member of the small library produced was prepared from amino-functionalized trityl resin reacting with a 4-phenyl Zincke salt to give resin-bound product 62 (Scheme 8.4.21). After ion exchange and cleavage from the resin, pyridinium 63 was isolated. Alternatively, borohydride reduction of 62 led to the 1,2,3,6-tetrahydropyridine 64, which could be hydrogenated to the corresponding piperidine 65. 

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