66178-41-4Relevant articles and documents
The effect of deuteration on the keto-enol equilibrium and photostability of the sunscreen agent avobenzone
Murphy, Rhys B.,Staton, John,Rawal, Aditya,Darwish, Tamim A.
, p. 1410 - 1422 (2020)
The remarkable properties of deuterium have led to many exciting and favourable results in enhancing material properties, for applications in the physical, medical, and biological sciences. Deuterated isotopologues of avobenzone, a sunscreen active ingredient, were synthesised to examine for any changes to the equilibrium between the diketone and enol isomers, as well as their UV photostability and photoprotective properties. Prior to UV irradiation, deuteration of the diketone methylene/enol moiety (i.e. avobenzone-d2) led to an increase in the % diketone compared to non-deuterated, determined by 1H NMR experiments in CDCl3 and C6D12. This can be rationalised from two angles; mechanistically by a deuterium kinetic isotope effect for the CH vs. CD abstraction step during tautomerisation from the diketone to the enol, and a weaker chelating hydrogen bond for the enol when deuterated allowing increased equilibration to the diketone. Avobenzone-d2 was further examined by solid state 13C NMR. The higher % diketone for avobenzone-d2 was postulated to favour increased photodegradation by a non-reversible pathway. This was investigated by UV irradiation of the avobenzone isotopologues in C6D12, both in real time in situ within the NMR by fibre optic cable as well as ex situ using sunlight. An increase in the relative amount of photoproducts for avobenzone-d2 compared to non-deuterated was observed by 1H NMR upon UV irradiation ex situ. Overall, the study demonstrates that deuteration can be applied to alter complex equilibria, and has potential to be manifested as changes to the properties and behaviour of materials.
Dimensional Reduction of Lewis Acidic Metal-Organic Frameworks for Multicomponent Reactions
Feng, Xuanyu,Song, Yang,Lin, Wenbin
supporting information, p. 8184 - 8192 (2021/06/27)
Owing to hindered diffusions, the application of porous catalytic materials has been limited to relatively simple organic transformations with small substrates. Herein we report a dimensional reduction strategy to construct a two-dimensional metal-organic framework (MOF), Zr6OTf-BTB, with 96% accessible Lewis acidic sites as probed by the bulky Lewis base pivalonitrile. With nearly free substrate accessibility, Zr6OTf-BTB outperformed two three-dimensional MOF counterparts of similar Lewis acidity (Zr6OTf-BPDC and Zr6OTf-BTC) in catalyzing sterically hindered multicomponent reactions (MCRs) for the construction of tetrahydroquinoline and aziridine carboxylate derivatives with high turnover numbers (TONs). Zr6OTf-BTB was also superior to the homogeneous benchmark Sc(OTf)3 with nearly 14 times higher TON and 9 times longer catalyst lifetime. Furthermore, the topology-activity relationships in these Zr-based Lewis acidic MOFs were rationalized by comparing their Lewis acidity, numbers of Lewis acidic sites, and sterically accessible Lewis acidic sites. Zr6OTf-BTB was successfully used to construct several bioactive molecules via MCRs with excellent efficiency. This dimensional reduction strategy should allow the development of other MOF catalysts for synthetically useful and complicated organic transformations.
Dicationic Thiolate-Bridged Diruthenium Complexes for Catalytic Oxidation of Molecular Dihydrogen
Yuki, Masahiro,Sakata, Ken,Nakajima, Kazunari,Kikuchi, Syoma,Sekine, Shinobu,Kawai, Hiroyuki,Nishibayashi, Yoshiaki
, p. 4499 - 4506 (2017/12/05)
Dicationic thiolate-bridged diruthenium complexes bearing sterically bulky alkane substituents on the thiolate ligands such as [Cp?Ru(μ-SiPr)2Ru(OH2)Cp?](OTf)2 have been found to work as effective catalysts toward oxidation of molecular dihydrogen into protons and electrons in protic solvents such as water and methanol. DFT calculations indicate that the sterically bulky alkane substituent in the complex plays an important role in facilitating the reaction step of the coordination of molecular dihydrogen.
Hidden Bronsted acid catalysis: Pathways of accidental or deliberate generation of triflic acid from metal triflates
Dang, Tuan Thanh,Boeck, Florian,Hintermann, Lukas
experimental part, p. 9353 - 9361 (2012/01/04)
The generation of a hidden Bronsted acid as a true catalytic species in hydroalkoxylation reactions from metal precatalysts has been clarified in case studies. The mechanism of triflic acid (CF3SO3H or HOTf) generation starting either from AgOTf in 1,2-dichloroethane (DCE) or from a Cp*RuCl2/AgOTf/phosphane combination in toluene has been elucidated. The deliberate and controlled generation of HOTf from AgOTf and cocatalytic amounts of tert-butyl chloride in the cold or from AgOTf in DCE at elevated temperatures results in a hidden Bronsted acid catalyst useful for mechanistic control experiments or for synthetic applications.
Spectroscopic Studies on Monofluoroammonium Salts
Minkwitz, Rolf,Nass, Ruediger
, p. 1558 - 1563 (2007/10/02)
The NMR, IR and Raman spectra of several NH3F(+)X(-) salts are reported.The preparation of NH3F(+)SO3Cl(-) and NH3F(+)SO3F(-) is described. - Key words: NMR Spectra, Raman Spectra, IR Spectra