Triarylcarbenium salts highly reducible by primary alcohols

Abstract

The carbenium salts [Ph{2,2C6H3}2C]X (X = C104, BF4), prepared from Ph[2,6-(Me0)2C6H3]2COH and a slight excess of acid in propan-2-01, have been reduced in primary alcohol or methanol much faster than the related triarylcarbenium salts t o give Ph[2,6-(Me0)2C6H3]2CH and the aldehyde.

New stable, isolable triarylmethyl based dyes absorbing in the near infrared

“…The solution of 6a in chloroform in the absence of acid (entry 1, Table 1) had turned from orange to dark blue and its electronic spectrum now resembled that of the carbenium salt 7a, with an absorption in the NIR region (k max = 904 nm). This suggests the facile formation of the carbenium ion 7a from the carbinol even at neutral conditions, resembling behaviour already observed for tris(2,6-dimethoxyphenyl)methanol [17]. On the other hand, the solutions corresponding to entries 2-7 of Table 2 had all lost their colour intensity and the NIR band had disappeared.…”

“…Their UV spectra were all similar but did not resemble that of the carbinol 6a. A possibility could be that the carbenium salt is reduced to the corresponding triarylmethane, a reaction known to be possible in solvents such as alcohols, diethyl ether or tetrahydrofuran [17]. Although this is still to be confirmed for our compound, it might be plausible due to the small traces (0.6-1%) of ethanol present in the HPLC grade chloroform used for our dilutions.…”

“…The NIR band loses intensity and also blue shifts slightly (k max = 888 log e = 4.46 after one week and k max = 843 log e = 4.06 after 5 months for solution in entry 2 and k max = 792 log e = 4.24 after 5 months for solution in entry 4). This indicates that the specific samples were relatively stable especially compared to the corresponding ferrocenyl derivative in which, as mentioned previously, the solvent may be implicated in the appearance of secondary reaction products [17,21].…”

“…It is known that ortho methoxy groups in phenyl derivatives give unusual physical and chemical properties to the derivatives due to the steric and electronic effects of the substituents and Wada [17] has demonstrated that the number of methoxy substituents on phenyl groups influences the stability and reactivity of triphenylcarbenium salts while the greater basicity of tris-2,6-dimethoxyphenylmethanol compared to that of triphenylmethanol has been known for some time [18]. Considering this stability factor, we prepared ferrocene derivative 6a and the analogue 6b for comparison with the triarylmethanol derivatives that we had synthesised previously [19].…”

X-ray structure and conformational study of tris(2-(dimethylamino)phenyl)methanol salt derivatives: Roles of anions and hydrogen bond

“…And the intra-and inter-conformational conversion of them are affected by the intramolecular H-bond. It is well known that TAMols, such as tris(4-(dimethylamino)phenyl)methanol (crystal violet base), usually form triphenylmethyl cation under acidic condition [22,23]. However, accepting protons, the tertiary alcohol forms stable salts with acids [24].…”