Triptycene

The compound triptycene may be prepared as shown What is compound... 

Blackley548 measured the rates of deuteration of biphenylene, fluorene, tri-phenylene, and phenanthrene relative to o-xylene as 6.15 5.85 1.08 1.32, which is in very good agreement with the values of 8.80 7.00 - 1.14 which may be deduced from the detritiation data in Table 159, obtained using anhydrous trifluoroacetic acid. Aqueous trifluoroacetic acid (with the addition in some cases of benzene to assist solubility) was used by Rice550, who found that triptycene was 0.1 times as reactive per aromatic ring as o-xylene (cf. 0.13 derivable from Table 159) whereas the compound (XXXI) was 0.9 times as reactive as o-xylene. An exactly comparable measure is not available from Table 158, but dihydroanthracene (XXXII), which is similar, was 0.51 times as reactive as o-xylene and... 

In the case of triptycene derivatives such as 121, a complete 360° rotation of the aryl group around the O—aryl bond requires the aryl group to pass over three rotational... 

Intramolecular insertion has been reported. The positively charged carbon of the carbocation (23), generated from the diazonium salt of the triptycene compound (22), reacted with the CH3 group in close proximity with it. ... 

A chiral [4]pseudocatenane 16 was synthesized from chiral triptycene-based /m( crown ether) and three equivalents of hw[p-(but-3-enyloxy)benzyl]ammonium salt in CH2CI2 in the presence of Grubbs II catalyst, followed by reduction <06CEJ5603>. Several novel calix[4]arenocrowns were prepared by a simple one-pot reaction of calix[4]monohydroquinone diacetate with bw-tosylates, e.g. l,4-bw[2-(2-(2-(2-tosyloxy-ethoxy)ethoxy)ethoxy)ethoxy)benzene, in dry MeCN in the presence of NaOH the self-assembly into calix[4]areno[2]catenanes with a dicationic salt and />-bfr(bromomethyl)-benzene was also demonstrated <06TL6012>. 

To find more information about the influence of steric effects on the polymerization performance, catalyst 2 (5,6 triptycene indenyl hafnocene dichloride) was developed. 

The stable carbanions may belong in a special category since their stability is in most cases due to resonance, and the resonance has geometrical requirements that might or might not be the same as those of the bond hybridization of an ordinary carbanion. The central hydrogen of triptycene has none of the acidity of the central hydrogen of triphenylmethane.364... 

Encapsulation of squaraine 23a in diastereomeric triptycene-based tetralactam macrocycles 24a and 24b was described in [61], The synthesis of the macrocyclic hosts was done by the reaction of pyridine-2,6-dicarbonyl dichloride and 2,7-diaminotriptycene in dry THF with Et3N. Macrocycles 24a and 24b readily form... 

Xue M, Chen CF (2008) Triptycene-based tetralactam macrocycles synthesis, structure and complexation with squaraine. Chem Commun 46 6128-6130... 

Other structural concepts evolved, one of them being triptycenes (55). Here, additional wings are introduced into the molecules by Diels-Alder type reactions. The glass-forming properties are improved by the propeller-like rigid structure [89]. We end our overview of the different classes of molecular glasses with these materials and note that the number of published structures is growing every year. More details on the different materials can be found in one of the recent chemical reviews [102-104]. 

Contemporaneously with these studies, Iwamura (145) described the separation of the C2 and C2v isomers of 9,10-bis(l-cyano-l-methylethyl)triptycene (102). The Arrhenius activation energy for rotation obtained was 37.7 kcal/mol,... 

In order to see the effect of the peri substituent on the barrier to rotation, 2,3-dichloro-9-(l-cyano-l-methylethyl)triptycene and 2,3-dichloro-9-(l-meth-oxycarbonyl-l-methylethyl)triptycene (103, X = H, Y = Cl) were prepared (147). The data are included in Table 21. The barrier to rotation becomes definitely higher when the peri substituent is removed. Thus the peri substituent in... 

Kinetic Parameters for the Internal Rotation of 9-(l-Cyano- or 1-Methoxycarbonyl-l-methylethyl)triptycenes (103) in 1-Chloronaphthalene... 

Examination of the barriers to rotation of the cyano and methoxycarbonyl compounds reveals that the barriers are higher for the former if the peri substituent is the same. This may also be ascribed to a raising of the ground state energy caused by the methoxycarbonyl group extending into the gap between the two benzeno bridges of the triptycene skeleton. 

Close examination of the population ratios of the peri substituted compounds (Table 21) shows another point. That is, whereas the sc form of the methoxycarbonyl compound is less favored relative to that of the cyano compound when the peri substituent is methyl, the situation is reversed when the peri substituent is chlorine. Weak attractive interactions between a carbonyl moiety and a peri substituent bearing a lone pair of electrons are known in triptycene systems, and the methoxycarbonyl group is a stronger electron acceptor than cyano (148). This attractive interaction may be the cause for the seemingly anomalous populations. 

Establishing that a smaller substituent in the peri position can raise the barrier, Oki and co-workers (149) were interested in finding the peri substituent effect on the barrier to rotation, and prepared a series of 9-(l,l-dimethyl-2-phenyl-ethyl)triptycenes (104). Data in Table 22 indicate that the barrier to rotation... 

These results suggested examination of the buttressing effect in bromo compounds, so 1,2,3,4-tetrabromo- and l-bromo-9-(l,l-dimethyl-2-phenylethyl)-triptycenes were prepared. As expected, the tetrabromo compound had a relatively low barrier of 35.1 kcal/mol at 500 K. In contrast, the free energy of activation for rotation of the monobromo compound was 39.2 kcal/mol. The difference amounts to 4.1 kcal/mol (151). The reverse buttressing effect can be large if the substituents concerned are large. 

Since, in the case of the tm-butyltriptycene skeleton, the maximum barrier to rotation is realized when the substituent in the peri position is medium sized, it was of interest to see whether a similar result would be obtained with other tertiary alkyl groups. Thus to complete the series, 1,2,3,4-tetrafluoro- and l,4-dimethoxy-9-(l-cyano-l-methylethyl)triptycenes (103, X = Y = F or X = CH30, Y = H) were prepared. The fine energies of activation for rotation of the fluoro and the methoxy compounds were 39.9 and 38.9 kcal/mol, respectively, at 462 K (152). It may be too early to draw a general conclusion in the tertiary alkyl series, but it is tempting to consider that the highest barriers are obtained when the peri substituent in this series is fluorine. 

K for both compounds (155). These values are a little smaller than that for l,2,3,4-tetrachloro-9-(l,l-dimethyl-2-phenylethyl)triptycene(104,X = Y = Cl),... 

After finding that rotation of the rm-butyl group in dimethyl 9-rm-butyl-9,10-dihydro-9,10-ethenoanthracene-ll,12-dicarboxylate (95) was locked on the laboratory time scale, Oki and Suda introduced an isopropyl group in place of the rm-butyl group and found that the barrier was so much lowered ( , = 15.4 kcal/mol) that the attempt to isolate atropisomers had to be abandoned (140). Since then, triptycene systems have been found to give higher barriers to rotation than the ethenoanthracene system. Thus it became attractive to examine die barriers to rotation about a rec-alkyl-to-triptycyl bond. 

Compounds of type 111 should, in principle, be resolvable into stable enantiomers if the barrier is high enough. However, these compounds do not carry a functional group convenient for resolution. Oki and associates (162) modified one of the methyls in the isopropyl group to make the rotational isomers dia-stereomeric. They prepared 9-(2-methoxy-l-methylethyl)triptycenes (114) and... 

Kinetic Parameters for Rotation (ap — sc) and Population Ratios of 9-(2-Methoxy-l-methylethyl)triptycenes (114) in Chloroform- ... 

Oki and associates (163) further prepared 9-(l-methyl-2-propenyl) triptycenes (115) to see the effect of a vinyl substituent on the barrier to rotation. They were able either to isolate or to enrich one of the retainers in crystalline form, and they examined the barrier both by equilibration and by the dynamic NMR tech-... 

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