Triphenylmethylation

If triphenylmethyl chloride in ether is treated with sodium, a yellow colour is produced due to the presence of the anionic spiecies PhsC". Alternatively, if triphenylmethyl chloride is treated with silver perchlorate in a solvent such as THF, the triphenylmethyl cation is obtained. More conveniently, triphenylmethyl salts, PhsC X", can be obtained as orange-red crystalline solids from the action of the appropriate strong acid on triphenylcarbinol in ethanoic or propanoic anhydride solution. The perchlorate, fluoroborate and hexafluoro-phosphate salts are most commonly used for hydride ion abstraction from organic compounds (e.g. cycloheptatriene gives tropylium salts). The salts are rather easily hydrolysed to triphenylcarbinol. 

Von Baeyer (Nobel Prize, 1905) should be credited for having recognized in 1902 the saltlike character of the compounds formed. He then suggested a correlation between the appearance of color and salt formation—the so-called halochromy. Gomberg (who had just shortly before discovered the related stable triphenylmethyl radical), as well as Walden, contributed to the evolving understanding of the structure of related cationic dyes such as malachite green. 

The selectivity relationship merely expresses the proportionality between intermolecular and intramolecular selectivities in electrophilic substitution, and it is not surprising that these quantities should be related. There are examples of related reactions in which connections between selectivity and reactivity have been demonstrated. For example, the ratio of the rates of reaction with the azide anion and water of the triphenylmethyl, diphenylmethyl and tert-butyl carbonium ions were 2-8x10 , 2-4x10 and 3-9 respectively the selectivities of the ions decrease as the reactivities increase. The existence, under very restricted and closely related conditions, of a relationship between reactivity and selectivity in the reactions mentioned above, does not permit the assumption that a similar relationship holds over the wide range of different electrophilic aromatic substitutions. In these substitution reactions a difficulty arises in defining the concept of reactivity it is not sufficient to assume that the reactivity of an electrophile is related... 

Additional phenyl substituents stabilize carbocations even more Triphenylmethyl The triphenylmethyl group is 1, , t 11 1. . 1. .. 

Cesium forms simple alkyl and aryl compounds that are similar to those of the other alkah metals (6). They are colorless, sohd, amorphous, nonvolatile, and insoluble, except by decomposition, in most solvents except diethylzinc. As a result of exceptional reactivity, cesium aryls should be effective in alkylations wherever other alkaline alkyls or Grignard reagents have failed (see Grignard reactions). Cesium reacts with hydrocarbons in which the activity of a C—H link is increased by attachment to the carbon atom of doubly linked or aromatic radicals. A brown, sohd addition product is formed when cesium reacts with ethylene, and a very reactive dark red powder, triphenylmethylcesium [76-83-5] (C H )2CCs, is formed by the reaction of cesium amalgam and a solution of triphenylmethyl chloride in anhydrous ether. 

Photochromism Based on Dissociation Processes. Both heterolytic and homolytic dissociation processes can result in the generation of a photochromic system. An example of an heterolytic process is the reversible formation of triphenylmethyl cation, by photolysis of... 

Thiazole, 4-methyl-5-(2-hydroxyethyl)-in thiamine biosynthesis, 1, 97 Thiazole, 4-methyl-2-methylami nosynthesis, 6, 300 Thiazole, 4-methyl-2-phenyl-alkylation, 6, 256 mercuration, 6, 256 Thiazole, 2-(methylthio)-methylation, 6, 290 thermodynamic values, 6, 291 Thiazole, 2-methylthio-5-phenyl-synthesis, 5, 153 Thiazole, 4-methyl-5-vinyl-occurrence, 6, 327 Thiazole, 2-phenyl-acetylation, 6, 270-271 Conformation, 6, 237 synthesis, 5, 113, 6, 306 Thiazole, 4-phenyl-conformation, 6, 237 2,5-disubstituted synthesis, 6, 304 Thiazole, 5-phenyl-conformation, 6, 237 Thiazole, 2-phenyl-5-triphenylmethyl-synthesis, 6, 265 Thiazole, 2-(2-pyridyl)-metal complexes, 5, 51 6, 253 Thiazole, 4-(2-pyridyl)-metal complexes, S, 51 6, 253 Thiazole, tetrahydro-ring cleavage, 5, 80 Thiazole, 2,4,5-trimethyl-occurrence, 6, 327... 

BAEYER VILLIGER Tritylalion Introduction of a triphenylmethyl group into an aromatic ring... 

Some of the original work in the carbohydrate area in particular reveals extensive protection of carbonyl and hydroxyl groups. For example, a cyclic diacetonide of glucose was selectively cleaved to the monoacetonide. A summary describes the selective protection of primary and secondary hydroxyl groups in a synthesis of gentiobiose, carried out in the 1870s, as triphenylmethyl ethers. 

C5H5N CPh3BF4, CH3CN, Pyr, 60-70°, 75-90% yield. Triphenylmethyl ethers can be prepared more readily with triphenylmethylpyridinium fluo-roborate than with triphenylmethyl chloride-pyridine. 

Triphenylmethyl esters are unstaole in aqueous solution, but are stable to oxy-mercuration. ... 

The 2,4,6-trimethylbenzyl ester has been prepared from an amino acid and the benzyl chloride (Et3N, DMF, 25°, 12 h, 60-80% yield) it is cleaved by acidic hydrolysis (CF COOH, 25°, 60 min, 60-90% yield 2 N HBr/HOAc, 25°, 60 min, 80-95% yield) and by hydrogenolysis. It is stable to methanolic hydrogen chloride used to remove A-o-nitrophenylsulfenyl groups or triphenylmethyl esters. ... 

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