Arylmethanes

Addition of carboxylic acids to alkynes Acylation of aldehydes or ketones Bisdecarboxylation of malonic acids Oxidation of arylmethanes with CrOs and AC2O... 

Oxidation of Arylmethanes - Electrochemical Alternative Routes to the Etard Reaction... 

Drivers for Performing the Electrochemical Oxidations of Arylmethanes in Micro Reactors... 

The first study on the oxidation of arylmethanes used this reaction as a model to show the general advantages of electrochemical micro processing and to prove the feasibility of an at this time newly developed reactor concept [69]. Several limits of current electrochemical process technology hindered its widespread use in synthetic chemistry [69]. As one major drawback, electrochemical cells stiU suffer from inhomogeneities of the electric field. In addition, heat is released and large contents of electrolyte are needed that have to be separated from the product. 

Beneficial Micro Reactor Properties for Electrochemical Oxidations of Arylmethanes... 

Electrochemical Oxidations of Arylmethanes Investigated in Micro Reactors Organic synthesis 85 [OS 85] Oxidation of4-methoxy toluene to 4-methoxy benzaldehyde... 

Arylmethane leuco dyes are converted into di- or triarylmethane dyes on oxidation. This class of dye precursors sometimes is referred to as leuco di- or triphenylmethane dyes, or di- or triphenylmethane leuco dyes. The use of the term di- or triarylmethane dyes can be misleading as the central carbon atom is a carbonium ion. Instead, the term di- and triarylmethine dye is recommended for this class as it correlates with the well-known polymethine dyes. Nevertheless, it has not been commonly used. 

Burkhouse, D. and Zimmer, H., Novel synthesis of 1-alkoxy-l-arylmethane-phosphonic acid esters, Synthesis, 330, 1984. 

Aryl chlorothioformates, 23 628 Aryl complexes, zirconium, 26 655 Aryl ethers, uses for, 70 581 2-Arylglycine esters, 72 166 Aryl halide amination, 9 278 Aryl halides, reaction with carbon monoxide, 5 11 Arylhydrazines, 9 270 Arylmethane dyes, 9 503... 

On the other hand, to constrain the cyclic, the blocking group (BG) has to be bulkier than the cavity of the cyclic molecule. Harrison found that a trityl group can only block cyclics up to 28-membered whereas the tris(p-t-butylphenyl)-methyl moiety can effectively constrain 42-membered cyclics [3, 13, 14]. These results have been widely applied as a guide in the preparation of polyrotaxanes e.g., monofunctional [18, 19] and difimctional [19—23] BG based on tri- and tetra-arylmethane derivatives were successfully prepared and used as end groups and in-chain units, respectively, to constrain crown ethers in a variety of polyrotaxanes. 

As early as 1903, heating toluene and sulfur in a sealed vessel was shown by Fromm and coworkers to lead to a compound later identified as 2-phenylbenzo[6]thiophene (280). Other arylmethanes also undergo this reaction. For example, 2-methylnaphthalene and sulfur gave (281). By-products include 1,2-diphenylethane, 2,2 -dimethylbiphenyl, stilbene and tetraphenylthiophene, in the case of toluene. The coupled products suggest a radical mechansim (49JOC761). 

The preparation of tri arylmethane dyes proceeds through several stages formation of the colorless leuco base in acid media, conversion to the colorless carbinol base by using an oxidizing agent, e.g., lead dioxide, manganese dioxide, or alkali dichromates, and formation of the dye by treatment with acid. The oxidation of the leuco base can also be accomplished with atmospheric oxygen in the presence of catalysts. 

The acid strengths of arylmethanes are listed in Table 26-3. All are quite weak acids relative to water but vary over many powers of ten relative to one another. The stronger acids form the more stable carbanions, and the carbanion stability generally is determined by the effectiveness with which the negative charge can be delocalized over the substituent aryl groups. 

Benzene (1) is the simplest aromatic hydrocarbon upon which our knowledge of aromatic chemistry is based. This hydrocarbon, the alkylbenzenes (2), the arylmethanes [e.g. diphenylmethane (3)], the biphenyls [e.g. biphenyl (4)] and the condensed polycyclic systems [e.g. naphthalene (5) and anthracene (6)] all exhibit chemical reactivity and spectroscopic features which are markedly different from their aliphatic and alicyclic hydrocarbon counterparts. Indeed the term aromatic character was introduced to specify the chemistry of this group of hydrocarbons and their substituted functional derivatives, and it was soon used to summarise the properties of certain groups of heterocyclic compounds having five- and six-membered ring systems and the associated condensed polycyclic analogues (Chapter 8). 

Eine Synthese fur cyclische Phosphinsauren stellt die Wasser-Abspaltung aus 2-Aryl-arylmethan-phosphonsauren dar. Die Ausbeuten sind aufgrund der erforderlichen hohen Reaktionstemperaturen von iiber 350° teilweise nur maBig ... 

The well-known indicator phenolphthalein (8) is an example of tri-arylmethane dyes which represents a cyanine-type chromogen and does not fluoresce. If an oxygen bridge is introduced between the upper benzene rings, the intensely green fluorescing flourescein (1) results. 

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