98293-92-6Relevant academic research and scientific papers
Niobium Pentachloride Mediated (Hetero)aromatic Aldehyde Friedel-Crafts Hydroxyalkylation with Arenes: An Efficient Strategy to Synthesize Triarylmethanes
Baviera, Giovanni S.,Donate, Paulo M.,Matias, Alexandre A.,Previdi, Daniel,Rodrigues, Shirley M. M.
, p. 4498 - 4506 (2019)
Niobium pentachloride is an efficient and useful Lewis acid to conduct Friedel-Crafts hydroxyalkylation between arenes and (hetero)aromatic aldehydes, to generate triarylmethanes. This practical methodology offers several advantages, such as short reaction time, mild experimental conditions, and excellent yields.
Acidities and Homolytic Bond Dissociation Energies (BDEs) of Benzyl-Type C-H Bonds in Sterically Congested Substrates
Bordwell, F. G.,Cheng, Jin-Pei,Satish, A. V.,Twyman, Cary L.
, p. 6542 - 6546 (2007/10/02)
Equilibrium acidities in DMSO and BDEs for the benzylic C-H bonds are reported for 19 triphenylmethanes, three 9,10-dihydroanthracenes, and nine xanthenes.The phenyl groups in triphenylmethane, 9-phenyl-9,10-dihydroanthracene, and 9-phenylxanthene are shown to be constrained in their ability to delocalize either the negative charges in the anions formed by loss of a proton or the odd electrons released by loss of hydrogen atom.Analysis of the pKHA values showed, however, that strong solvation of para electron-withdrawing substituents in a phenyl ring of each of these substrates caused the corresponding anion to adopt a conformation where effective conjugative overlap occured between the substituent and the carbanion via the phenyl ring.In other words a conformational change was induced via a substituent solvation assisted resonance (SSAR) effect.In sharp contrast to these large solvation-induced substituent effects on anion stabilities, remote substituent effects on radical stabilities in these congested species were found to be negligible.Substitution of either a p-toluenesulfonyl or CN group into the 9-position of xanthene caused a large increase in acidity, but the p-CH3C6H4SO2 group caused an increase in the BDE of the acidic C-H bond, whereas the CN group caused a small decrease.
