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101.
This article describes the rational design of first generation systems for oxidatively induced Aryl-CF(3) bond-forming reductive elimination from Pd(II). Treatment of (dtbpy)Pd(II)(Aryl)(CF(3)) (dtbpy = di-tert-butylbipyridine) with NFTPT (N-fluoro-1,3,5-trimethylpyridinium triflate) afforded the isolable Pd(IV) intermediate (dtbpy)Pd(IV)(Aryl)(CF(3))(F)(OTf). Thermolysis of this complex at 80 °C resulted in Aryl-CF(3) bond-formation. Detailed experimental and computational mechanistic studies have been conducted to gain insights into the key reductive elimination step. Reductive elimination from this Pd(IV) species proceeds via pre-equilibrium dissociation of TfO(-) followed by Aryl-CF(3) coupling. DFT calculations reveal that the transition state for Aryl-CF(3) bond formation involves the CF(3) acting as an electrophile with the Aryl ligand serving as a nucleophilic coupling partner. These mechanistic considerations along with DFT calculations have facilitated the design of a second generation system utilizing the tmeda (N,N,N',N'-tetramethylethylenediamine) ligand in place of dtbpy. The tmeda complexes undergo oxidative trifluoromethylation at room temperature. 相似文献
102.
Li Y Al-Eryani R Yarbrough ML Orth K Ball HL 《Journal of the American Society for Mass Spectrometry》2011,22(4):752-761
Recent studies have suggested that adenosine 5'-monophosphate (AMP) post-translational modification of proteins could represent
a novel molecular signaling pathway. Mass spectrometric fragmentation characteristics of this modification have not previously
been described and studied systematically. In this work, we therefore examined the fragmentation pattern of chemically synthesized
peptides containing AMPylated Thr, Ser, and Tyr. The formation of characteristic ions and the influence of collision energy
(CE) on the detection of characteristic ions and their relative peak intensity are reported. When peptide with AMPylated Ser/Thr
underwent collision induced dissociation (CID), peaks at m/z 348.1, 136.1, and 250.1, fragments with AMP group attached, and fragments consistent with neutral loss of 347 Da were major
characteristic ions; fragments consistent with neutral loss of 135 Da or 249 Da were weaker and not always detectable. The
observations for Tyr AMPylation followed the same general patterns as those for Ser/Thr modification, with the exception that
the ions detected for Tyr AMPylation did not include either the peak at m/z 348.1, or fragments with a mass shift of –347 Da. The results described in this paper highlight a series of diagnostic ions,
which can be used not only to confidently identify the AMPylation site based on MS and MS/MS data, but also to selectively
scan AMPylated peptides in complex protein mixtures. 相似文献
103.
This paper describes the 1,1-arylacetoxylation of diverse α-olefins using organostannanes and hypervalent iodine oxidants. The reaction provides a convergent approach for generating a C-C and a C-O bond as well as a new stereocenter in a single catalytic transformation. 相似文献
104.
The silver-mediated C-H trifluoromethylation of aromatic substrates using TMSCF(3) is described. The development, optimization, and scope of these transformations are reported. AgCF(3) intermediates are proposed. 相似文献
105.
106.
Sean Cleary Susan Hermiller Melanie Stein Jennifer Taback 《Mathematische Zeitschrift》2011,269(3-4):879-915
We give the first examples of groups which admit a tame combing with linear radial tameness function with respect to any choice of finite presentation, but which are not minimally almost convex on a standard generating set. Namely, we explicitly construct such combings for Thompson??s group F and the Baumslag?CSolitar groups BS(1, p) with p ??? 3. In order to make this construction for Thompson??s group F, we significantly expand the understanding of the Cayley complex of this group with respect to the standard finite presentation. In particular we describe a quasigeodesic set of normal forms and combinatorially classify the arrangements of 2-cells adjacent to edges that do not lie on normal form paths. 相似文献
107.
Arion T Mucke M Förstel M Bradshaw AM Hergenhahn U 《The Journal of chemical physics》2011,134(7):074306
We report the occurrence of interatomic Coulombic decay (ICD) in mixed NeKr clusters. A well-defined feature ranging from 9 to 12 eV in kinetic energy is observed in coincidence with the Ne 2s photoelectrons. It derives from an ICD process, in which an initial Ne 2s vacancy is filled by a Ne 2p electron and an electron is emitted from a 4p level on a neighboring Kr atom. We have studied the dependence of the effect on photon energy, cluster composition, and cluster size. Interestingly, the ICD electron energy increases slightly and grows a shoulder on going from 2% to 5% Kr in the coexpansion process, which we interpret in terms of surface versus bulk effects. 相似文献
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