0-Triphenylmethyl derivatives preparation

Rubidium triphenylmethyl, RbCPhg, prepared in a similar manner to the lithium compound, is a dark-red powder resembling the sodium and potassium derivatives. It gives a blood-red solution in ether. 

B, Preparation of S olid Derivatives, such as a)Esters of benzoic acid and nitrobenzoic acids (p331) b)Alkyl N-Arylcarbamates (Phenyl- and a-Naph-thy lure thanes) (p331) and e)Bis (triphenylmethyl) Esters (p332)... 

The parent system is prepared by oxidation of tetrahydrothiopyran with triphenylmethane and perchloric acid (66HCA2046) in high yield, and the method is applicable to the preparation of virtually all simple alkyl or aryl derivatives. In more complex cases, especially where the strong acid might cause elimination or isomerization side reactions, triphenylmethyl tetrafluoroborate may be used with the thiin precursor (equation 113) (78CL723). 

Pracejus and co-workers also described an alternative method for preparing suitable enolates in situ, Michael addition of a thiol to an acrylate [8]. A selected example of this reaction, for which enantioselectivity is in the range 20-54% ee, is shown in Scheme 9.3, Eq. (a). Use of a catalytic amount (5 mol%) of quinidine, 7, gave the (R)-cysteine derivative 6 with 54% ee. Benzyl thiol, benzhydryl thiol, or triphenylmethyl thiol were used as the thiol component. In addition to acrylates, nitroalkenes were used as a starting material. 

Most reported phthalocyanine derivatives (sulfo-, nitro-, amino-, triphenylmethyl-, polymeric, etc.) are copper complexes, although at present the synthetic chemistry of other d- and /-metal Pc derivatives is being rapidly developed (Examples 30-36) [5,6,116-118]. Some of them (in particular, copper phthalocyanine sulfonic acids) are of industrial interest because of their usefulness as dyes. Phthalocyanine sulfonic acids themselves are prepared both by urea synthesis from sulfonated phthalic anhydride and by the sulfonation of the phthalocyanine [6], Some substituted metal phthalocyanines can be obtained by chemical or electrochemical reduction [118e]. Among a number of reported peculiarities of substituted phthalocyanines, the existence of three electronic isomers for magnesium derivative PcMn was recently confirmed [118f]. 

Secondary trityl ethers can best be prepared by reaction with triphenylmethyl perchlorate, but these derivatives tend to be rather labile.2... 

As with triphenylmethyl salts, the hexachlorantimonate derivative of tropylium ion is by far the most convenient to handle and to use as a catalyst. In this case, thermal decomposition or hydrolysis of the tropylium salt is almost nonexistent under ordinary conditions, and the catalyst can be prepared conveniently, purified, and stored over long... 

R,4R)-4-(Isobutylthio)- and -(isobutylsulfonyl)-3-(triphenylmethyl-amino)azetidin-2-one derivatives were previously prepared (2). 

Both the results and the reasoning, however, were rigorously confirmed shortly thereafter. Eventually it became clear that Gomberg s synthetic failure led to the discovery of stable radicals, a new class of organic species, derivatives of trivalent carbon. Further studies led to the understanding that the triarylmethyl system is extremely versatile and gives rise to the preparation of other types of derivatives of trivalent carbon, e.g. salts of the triphenylmethyl cation 66b and the triphenylmethyl anion 66c. 

The triphenylmethyl ethers of the carbohydrates constitute a group of derivatives of particular interest because of the special properties inherent in the trityl group. Before entering into a discussion of these carbohydrate derivatives, a few words regarding the preparation, properties and special behavior of trityl ethers would appear to be in order. 

Pyrylium phosphonic acids (60a) have been prepared by the reaction of triethyl phosphite with pyrylium salts followed by oxidation of the product (either before or after hydrolysis) with the triphenylmethyl carbonium ion. This approach has been used to obtain the analogous thiopyrylium phos-phonates (60b) and the cyclopropene and tropylidene derivatives (61) and (62). The enamine phosphonates (63) are readily accessible from addition... 

The cation (XXXIV) was obtained by deprotonation of a benzocyclo-butenocycloheptatriene, using triphenylmethyl hexafluorophosphate [196], N.m.r. spectra indicate that it is best regarded as possessing two essentially independent 6 ir-electron systems. A benzo--derivative of (XXXIV) has also been prepared in solution [197]. 

In a related study,the effect of attaching para-substituted phenyl groups directly to the 2-position of the 4-phenyl-l,3-dithiolium cation has been examined. As expected, electron-rich aryl groups tend to stabilize the cations in water. The methods used for the preparation of the 2-aryl-l,3-dithiolium salts (66) are of interest. These include the action of Grignard reagents on 2-methoxy-4-phenyl-l,3-dithiole (65) followed by hydride abstraction with triphenylmethyl perchlorate, and the reaction of 4-phenyl-1,3-dithiolium perchlorate (67) with appropriately activated benzene derivatives (e.g. phenol, anisole, and aniline). Treatment of 2-p-hydroxy-phenyl-4-phenyl-l,3-dithiolium perchlorate with triethylamine yields the red quinonoid compound (68). 

Ort/io-substituted benzaldehyde complexes have been prepared in high enantiomeric purity (97% ee), and in a one-pot sequence, from an optically pure hydrazone derivative, readily available from -q -benzaldehyde chromium tricarbonyl and SAMP [(S)-l-amino-2-(methoxymethyl)pyrrolidine]. The novelty derives from the combined use of a diastereoselective orthoaddition reaction of an organolithium nucleophile and a hydride abstraction with a triphenylmethyl cation. The subsequent acid hydrolysis serves to remove the hydrazone group, thus liberating the aldehyde functionality (Scheme 6.13). 

Other Alkyl and Aryl Ethers. - The preparation of selectively 0-alkylated saccharides, including benzyl, allyl, triphenylmethyl, and arylalkyl ethers has been reviewed. Analogues of lipids A and X incorporating 3-O-alkyl (rather than acyl) linkages have been described, and some carbohydrate monoalcohol derivatives have been alkylated with haloacetic acid ester derivatives. ° 3-C -Carboxymethyl D-glucose and D-fhictose compounds have been coupled via the carboxylic acid group to L-lysine in a search for acrosin inhibitors."... 

---