0-Triphenylmethyl derivatives

All polycyclic pigments, with the exception of triphenylmethyl derivatives, comprise anellated aromatic and/or heteroaromatic moieties. In commercial pigments, these may range from systems such as diketopyrrolo-pyrrol derivatives, which feature two five-membered heteroaromatic fused rings (DPP pigments) to such eight-membered ring systems as flavanthrone or pyranthrone. The phthalo-cyanine skeleton with its polycylic metal complex is somewhat unique in this respect. 

This reaction has been used to make crystalline triphenylmethyl derivatives that have been characterized by X-ray structure determinations,22 and a technique has been developed for the reduction of hydrocarbons by liquid cesium activated by ultrasound irradiation in the presence of ethers such as diglyme.23 The blue solutions obtained when cesium metal is dissolved in THF in the presence of [18]-crown-6 have been used to metallate a series of 1,4- or 1,5-hexadienes. The organocesium compounds have not been isolated but they have been identified by derivatization by carbonation and trimethylsilylation.24 Substituted cyclopentadienyl derivatives of sodium have also been synthesized by this method.25... 

Fig. 6. Molecular structures of the triphenylmethyl derivatives KCPh3.PMDTA.THF 8, RbCPh3.PMDTA 9, and CsCPh3.PMDTA 10. (Reprinted with permission from D. Hoffmann et al., Organomeiallics 1993, 12, 1193. Copyright 1993 American Chemical Society.)...

Amines can also be protected from unwanted acylation or from twofold alkylation by alkylation with a sterically demanding group that is amenable to selective removal after completion of the synthesis. The most commonly used groups for this purpose are triphenylmethyl derivatives. Amines are readily tritylated using trityl chloride in the presence of a tertiary amine. Deprotection is achieved by treatment with dilute... 

Selectivity data may be also employed to confirm or rule out the existence of a single intermediate in a number of closely related reactions. Thus the ability of the leaving group to influence the selectivity of the competitive attack of water and borohydride in the reaction of a number of diphenylmethyl derivatives testifies to the fact that attack occurs at the ion pair stage and not on the free carbocation (Bell and Brown, 1966). The dependence of the ratio kti/k-w on the leaving group in the solvolysis of a number of triphenylmethyl derivatives leads to the same conclusion regarding the triphenylmethyl system (Hill, 1965). 

However, the acidities of the benzyltriphenylphosphonium cation (pATa = 17.4) and of diethyl benzylphosphonate (pATa = 27.6) are sufficiently different to throw into question the likelihood of deprotonation of diethyl benzylphosphonate by the radical anion of 1. On the basis of a detailed study of the processes associated with the reduction of 1 (discussed later), it is likely that the effective base may well be the much more basic triphenylmethyl-derived carbanion, 4 in Scheme 20 (pATa of PI13CH = 30.6). This may possibly be produced by adventitious protonation of the fuchsone radical anion. Alternatively, the active EGB may be the dianion formed by disproportionation. 

D-Berine methyl ester is converted into the IJ-triphenylmethyl derivative which, when heated in the presence of methane sulphonyl chloride, yielded the substituted ethylene-amine (2). Reaction of (2) with hydroxyl-amine and sodium methoxide gives the corresponding hydroxamic acid (3) This product is converted, by the action of hydrochloric acid, into D-a amiso-3-chloro-H-hydroxypropionamide (k), which undergoes cyclization to D-cycloserine (5) when treated with a strongly basic ion exchange resin. 

Organoalkaline-Earth Initiators Both styrene and 1,3-dienes can be polymerized by organoalkaline-earth metal compounds, specifically those of magnesium, calcium, barium, and strontium. In general, hydrocarbon-soluble benzyl, 1,1-diphenylalkyl and triphenylmethyl derivatives have been investigated. For example, the adduct of 1,1-diphenylethylene (DPE) with dibenzylbarium, that is, bis(l,l,3-triphenylpropyl)barium, is hexane-soluble and polymerizes styrene with controlled molecular... 

Yet another type of hydrocarbyl bridging has been established for some solvated triphenylmethyl derivatives of the heavier alkali metals. [NaCPh3(tmeda)] , 64, and [KCPh3(diglyme)] , 66 [57], are supramolecularly associated into zigzag chains by weak intermolecular sodium-carbon contacts. 

Diphenylmethyl Derivatives Triphenylmethyl Derivatives Picolyl Derivatives Acetamidomethyl Derivatives... 

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