149099-27-4Relevant articles and documents
Solvolytic Behavior of Aryl and Alkyl Carbonates. Impact of the Intrinsic Barrier on Relative Reactivities of Leaving Groups
Mati?, Mirela,Kati?, Matija,Denegri, Bernard,Kronja, Olga
, p. 7820 - 7831 (2017)
The effect of negative hyperconjugation on the solvolytic behavior of carbonate diesters has been investigated kinetically by applying the LFER equation log k = sf(Ef + Nf). The observation that carbonate diesters solvolyze faster than the corresponding carboxylates and that the enhancement of aromatic carbonates is more pronounced indicates that the negative hyperconjugation and π-resonance within the carboxylate moiety is operative in TS. The plots of ΔG? vs approximated ΔrG° for solvolysis of benzhydryl aryl/alkyl carbonates and benzhydryl carboxylates reveal that a given carbonate solvolyzes over the higher Marcus intrinsic barrier and over the earlier transition state than carboxylate that produces an anion of similar stability. Due to the lag in development of the electronic effects along the reaction coordinate, the impact of the intrinsic barrier on solvolytic behavior of carbonates is more important than in the case of carboxylates and phenolates. Consequently, the solvolytic reaction constants (sf) are generally lower for carbonates than for carboxylates. Because of considerable lower reaction constants of carbonates, an inversion of relative reactivities between aryl/alkyl carbonate and another leaving group of similar nucleofugality (Nf) may occur if the electrofuge moiety of a substrate is switched.
Remarkable electronic effect on rhodium-catalyzed carbonyl additions and conjugated additions with arylmetallic reagents [15]
Huang,Meng,Venkatraman,Wang,Li
, p. 7451 - 7452 (2001)
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Mechanisms for the oxidation of secondary alcohols by dioxoruthenium(VI) complexes
Wang, Zhao,Chandler, W. David,Lee, Donald G.
, p. 919 - 928 (1998)
Possible mechanisms for the oxidation of alcohols by dioxoruthenium(VI) complexes are critically evaluated. Rate constants for the reduction of trans-[(TMC)Ru(VI)(O)2]++ (TMC = 1,4,8,11-tetramethyl-1,4,8,11- tetraazacyclotetradecane) by substituted benzhydrols are correlated more satisfactorily with Hammett σ substituent constants (p = -1.44 ± 0.08, r2 = 0.98) than with σ+ substituent constants (ρ = -0.72 ± 0.11, r2 = 0.83). Similar observations for the oxidation of substituted benzyl alcohols have recently been reported, confirming that the transition state for these reactions is not carbocation-like. Primary deuterium isotope effects indicate that cleavage of the α-C-H bond is rate-limiting. The lack of an observable O-D isotope effect and the ease of oxidation of ethers indicates that the presence of a hydroxyl is not essential. The previously reported observation that cyclobutanol is quantitatively converted into cyclobutanone by dioxoruthenium(VI) complexes eliminates free-radical intermediates from consideration as part of the mechanism, and negative entropies of activation (-ΔS(+) = 96-137 J mol-1 K-1) suggest a structured transition state. Only two of eight possible reaction mechanisms considered were found to be consistent with the available data. A critical analysis of the available data indicates that a 2 + 2 (C - H + Ru = O) addition and a reaction initiated by ligand formation through the interaction of the reductant's HOMO with the oxidant's LUMO are the most likely reaction mechanisms.
Melamine-Based Porous Organic Polymers Supported Pd(II)-Catalyzed Addition of Arylboronic Acids to Aromatic Aldehydes
Shen, Kai,Wen, Min,Fan, Chaogang,Lin, Shaohui,Pan, Qinmin
, p. 2612 - 2621 (2021/01/15)
Abstract: A new type melamine-based porous organic polymers (SZU-1) has been synthesized with melamine and 2,2′-bipyridyl-5,5′-dialdehyde by a one-pot method and fully characterized. Divalent palladium salts were coordinated to this polymer network which successfully catalyzed the nucleophilic addition reaction of arylboronic acids to aromatic aldehydes. With only 1.0?mol% heterogeneous catalyst loading, high reaction yields (>?85%) can be achieved in most cases. The scope of substrates was also investigated and the catalyst showed universal applicability. Graphic Abstract: The loose and porous melamine-based porous organic polymers (SZU-1) are synthesized by melamine and 2,2′-bipyridyl-5,5′-dialdehyde. The performance of SZU-1 was characterized and most of the substrates achieved high yield (> 85%) in the catalytic performance test.[Figure not available: see fulltext.]
Electronic Effect-Guided Rational Design of Candida antarctica Lipase B for Kinetic Resolution Towards Diarylmethanols
Li, Dan-Yang,Lou, Yu-Jiao,Xu, Jian,Chen, Xiao-Yang,Lin, Xian-Fu,Wu, Qi
supporting information, p. 1867 - 1872 (2021/02/12)
Herein, we developed an electronic effect-guided rational design strategy to enhance the enantioselectivity of Candida antarctica lipase B (CALB) mutants towards bulky pyridyl(phenyl)methanols. Compared to W104A mutant previously reported with reversed S-stereoselectivity toward sec-alcohols, three mutants (W104C, W104S and W104T) displayed significant improvement of S-enantioselectivity in the kinetic resolution (KR) of various phenyl pyridyl methyl acetates due to the increased electronic effects between pyridyl and polar residues. The electronic effects were also observed when mutating other residues surrounding the stereospecificity pocket of CALB, such as T42A, S47A, A281S or A281C, and can be used to manipulate the stereoselectivity. A series of bulky pyridyl(phenyl) methanols, including S-(4-chlorophenyl)(pyridin-2-yl) methanol (S-CPMA), the intermediate of bepotastine, were obtained in good yields and ee values. (Figure presented.).
Enhanced catalytic activity of one-dimensional CdS @TiO2 core-shell nanocomposites for selective organic transformations under visible LED irradiation
Eskandari, Parvin,Kazemi, Foad,Ramdar, Moosa,Zand, Zahra
, (2021/07/10)
In this study, we are interested in the photocatalytic activity under visible LED irradiation of one- dimensional (1D) CdS @TiO2 core–shell nanocomposites (CSNs) prepared through a facile and convenient method. For the synthesis of 1D CdS@TiO2 core/shell structure, titania source (Tetrabutyl titanate) was hydrolyzed by water vapor transmission on the surface of CdS nanowires (NWs) which were prepared via solvothermal method. The characterization of 1D CdS@TiO2 core–shell nanocomposites (CdS@TiO2 CSNs) was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis spectroscopy, and UV–Vis diffuse reflectance spectroscopy (DRS). The as-synthesized sample was utilized for the selective reduction of nitro compounds to benzimidazole and anilide, and also the reduction of benzophenones to alcohol under blue LED irradiation. The 1D CdS@TiO2 CSNs exhibited enhanced photoactivity compared with the pure TiO2, CdS nanowires and commercial TiO2-P25. The excellent reusability of the photocatalyst was examined for six runs. The results demonstrated that the prepared sample has the potential to provide a promising visible light-driven photocatalyst for other organic transformations.
