978-86-9Relevant academic research and scientific papers
Zirconium-catalysed direct substitution of alcohols: enhancing the selectivity by kinetic analysis
Camaj, David,Carlsson, Robin,Dalla-Santa, Oscar,Lill, Malin,Lundberg, Helena,Margarita, Cristiana,Ramstr?m, Anja,Tu?on, Hernando,Villo, Piret
, p. 7420 - 7430 (2021/11/23)
Kinetic analysis was used as a tool for rational optimization of a catalytic, direct substitution of alcohols to enable the selective formation of unsymmetrical ethers, thioethers, and Friedel-Crafts alkylation products using a moisture-tolerant and commercially available zirconium complex (2 to 8 mol%). Operating in air and in the absence of dehydration techniques, the protocol furnished a variety of products in high yields, including glycosylated alcohols and sterically hindered ethers. In addition, the kinetic studies provided mechanistic insight into the network of parallel transformations that take place in the reaction, and helped to elucidate the nature of the operating catalyst.
A [2]Rotaxane-Based Circularly Polarized Luminescence Switch
David, Arthur H. G.,Casares, Raquel,Cuerva, Juan M.,Campa?, Araceli G.,Blanco, Victor
supporting information, p. 18064 - 18074 (2019/11/19)
A rotaxane-based molecular shuttle has been synthesized in which the switching of the position of a fluorescent macrocycle on the thread turns "on" or "off" the circularly polarized luminescence (CPL) of the system while maintaining similar fluorescence profiles and quantum yields in both states. The chiroptical activity relies on the chiral information transfer from an ammonium salt incorporating d- or l-phenylalanine residues as chiral stereogenic covalent units to an otherwise achiral crown ether macrocycle bearing a luminescent 2,2′-bipyrene unit when they interact through hydrogen bonding. Each enantiomeric thread induces CPL responses of opposite signs on the macrocycle. Upon addition of base, the switching of the position of the macrocycle to a triazolium group disables the chiral information transfer to the macrocycle, switching "off" the CPL response. The in situ switching upon several acid/base cycles is also demonstrated.
Temperature Controls Guest Uptake and Release from Zn4L4 Tetrahedra
Zhang, Dawei,Ronson, Tanya K.,Güryel, Songül,Thoburn, John D.,Wales, David J.,Nitschke, Jonathan R.
supporting information, p. 14534 - 14538 (2019/10/11)
We report the preparation of triazatruxene-faced tetrahedral cage 1, which exhibits two diastereomeric configurations (T1 and T2) that differ in the handedness of the ligand faces relative to that of the octahedrally coordinated metal centers. At lower temperatures, T1 is favored, whereas T2 predominates at higher temperatures. Host-guest studies show that T1 binds small aliphatic guests, whereas T2 binds larger aromatic molecules, with these changes in binding preference resulting from differences in cavity size and degree of enclosure. Thus, by a change in temperature the cage system can be triggered to eject one bound guest and take up another.
High-yielding cleavage of (aryloxy)acetates
Spurg, Anke,Waldvogel, Siegfried R.
, p. 337 - 342 (2008/09/18)
A reliable and high-yielding one-pot sequence for the removal of O-carboxymethyl moieties from phenols is presented. When diethylphosphoryl azide is employed as the azide transfer reagent in the Curtius rearrangement and glycerol in the subsequent hydrolytic workup, the protocol can be reliably applied to a very broad scope of substrates. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
The rearrangement of N-triarylmethyl anilines to their p-triarylmethyl derivatives
Siskos, Michael G.,Tzerpos, Nikolaos I.,Zarkadis, Antonios K.
, p. 759 - 768 (2007/10/03)
The N-triarylmethyl anilines Ph3C-NHAr (Ar = Ph, o-Me-C6H4, m-Me-C6H4, p-Me-C6H4, p-O2N-C6H4, p-Ph3C-C6H4) and Ar'3C-NHPh tBu-C6H4)3C> prepared by the reaction of Ph3C-Cl with anilines ArNH2 and of the corresponding chlorides Ar'3C-Cl with aniline (at 50-100 deg C), undergo a Hoffmann-Martius rearrangement to p-triarylmethyl derivatives (i.e., p-Ar'3C-C6H4-NH2 for Ar = Ph) when they are heated (ca. 185 deg C) with equimolar amounts of PhNH3(1+)Cl(1-).The latter catalyses the rearrangement probably through the formation of the instable anilinium salt Ar'3C-NH2Ar(1+)Cl(1-) that serves as a Ar'3C(1+) ion source.Ar'3C(1+) in a second step (electrophilic aromatic substitution) leads with excess of ArNH2 to p-substituted derivatives (e.g. p-Ar'3C-C6H4-NH2).A free radical mechanism, resonable in view of the high temperatures used (ca. 185 deg C), could be excluded; Ar'3C-NHAr undergoes homolysis of the C-N bond to Ar'3C. radicals at temperatures higher than 200 deg C, a fact which was established using ESR spectroscopy and product analysis.
ALKYLATION OF PHENOL BY ALCOHOLS IN THE PRESENCE OF ALUMINUM PHENOLATE
Koshchii, V. A.,Kozlikovskii, Ya. B.,Matyusha, A. A.
, p. 1358 - 1361 (2007/10/02)
The reaction of phenol with alcohols in the presence of aluminum phenolate leads to a mixture of 2- and 4-alkylphenols, of which the former predominate in the case of benzyl, tert-butyl, and cyclohexyl alcohols, and the latter in the case of dimethylphenyl- and diphenylmethylcarbinols.Only triphenyl(4-hydroxyphenyl)methane is formed during the alkylation of phenol by triphenylcarbinol.In individual experiments the formation of small amounts of alkyl phenyl ethers and 2,6-dialkylphenols was observed.
