- Catalytic Enantioselective Synthesis of Heterocyclic Vicinal Fluoroamines by Using Asymmetric Protonation: Method Development and Mechanistic Study
-
A catalytic enantioselective synthesis of heterocyclic vicinal fluoroamines is reported. A chiral Br?nsted acid promotes aza-Michael addition to fluoroalkenyl heterocycles to give a prochiral enamine intermediate that undergoes asymmetric protonation upon rearomatization. The reaction accommodates a range of azaheterocycles and nucleophiles, generating the C?F stereocentre in high enantioselectivity, and is also amenable to stereogenic C?CF3 bonds. Extensive DFT calculations provided evidence for stereocontrolled proton transfer from catalyst to substrate as the rate-determining step, and showed the importance of steric interactions from the catalyst's alkyl groups in enforcing the high enantioselectivity. Crystal structure data show the dominance of noncovalent interactions in the core structure conformation, enabling modulation of the conformational landscape. Ramachandran-type analysis of conformer distribution and Protein Data Bank mining indicated that benzylic fluorination by this approach has the potential to improve the potency of several marketed drugs.
- Ashford, Matthew W.,Xu, Chao,Molloy, John J.,Carpenter-Warren, Cameron,Slawin, Alexandra M. Z.,Leach, Andrew G.,Watson, Allan J. B.
-
supporting information
p. 12249 - 12255
(2020/08/21)
-
- A highly practical and convenient halogenation of fused heterocyclic N-oxides
-
A novel, simple and practical method for the regioselective halogenation of fused heterocyclic N-oxides has been developed. It employs Vilsmeier reagent, generated in situ by POX3and DMF, as both the activating agent and the nucleophilic halide source. The method is amenable across a broad range of substrates, including quinolines, isoquinolines and the diazine N-oxides, possessing a variety of substitution patterns. Furthermore, all of the reagents associated are cheap and easy to obtain. The potential extension of this method to a one-pot oxidation/halogenation sequence that obviates the need for isolation of the N-oxide intermediates is also presented.
- Wang, Dong,Wang, Yuxi,Zhao, Junjie,Li, Linna,Miao, Longfei,Wang, Dong,Sun, Hua,Yu, Peng
-
p. 5762 - 5768
(2016/08/30)
-
- Aza-boron-diquinomethene complexes bearing N-aryl chromophores: Synthesis, crystal structures, tunable photophysics, the protonation effect and their application as pH sensors
-
A series of aza-boron-diquinomethene complexes (1a-1e) bearing different N-aryl chromophores were synthesized and characterized by multinuclear NMR spectroscopy, X-ray crystallography, optical absorption and emission spectroscopy, and elemental analysis. These robust thermal complexes possess tunable intense luminescence from blue to red with relatively high emission quantum yields. The introduction of different N-aryl chromophores into the aza-BODIQU core significantly tuned the emission colors. The relationship between their structures and properties was investigated systematically via spectroscopic methods and simulated by density functional theory (DFT) calculations. Additionally, the application of 1c as a pH sensor with a remarkable colour-changing property has been investigated. All these results indicate that these complexes exhibit robust thermal stability, tunable photophysical properties, relatively high photoluminescence quantum yields and protonation effect, making these complexes potential candidates for pH sensors, bioimaging probes and organic light-emitting materials.
- Zhu, Xiaolin,Huang, Hai,Liu, Rui,Jin, Xiaodong,Li, Yuhao,Wang, Danfeng,Wang, Qiang,Zhu, Hongjun
-
p. 3774 - 3782
(2015/04/22)
-
- Synthesis, photophysical and electrochemical properties of aza-boron-diquinomethene complexes
-
A series of aza-boron-diquinomethene (aza-BODIQU) complexes with different aryl-substituents (B1-B6) were synthesized and characterized. Their photophysical properties were investigated systematically via spectroscopic and theoretical methods. All complexes exhibit strong 1π-π* absorption bands and intense fluorescent emission bands in the visible spectral region at room temperature. The fluorescence spectra in solution show the mirror image features of the S0→S1 absorption bands, which can be assigned to the 1π-π*/1ICT (intramolecular charge transfer) emitting states. Except for B6, all complexes exhibit high photoluminescence quantum yields (ΦPL = 0.47-0.93). The spectroscopic studies and theoretical calculations indicate that the photophysical properties of these aza-BODIQUs can be tuned by the appended aryl-substituents, which would be useful for rational design of boron-fluorine complexes with high emission quantum yield for organic light-emitting applications.
- Wang, Danfeng,Liu, Rui,Chen, Chen,Wang, Shifan,Chang, Jin,Wu, Chunhui,Zhu, Hongjun,Waclawik, Eric R.
-
p. 240 - 249
(2013/10/21)
-
- Regioselective bromination of fused heterocyclic N-oxides
-
A mild method for the regioselective C2-bromination of fused azine N-oxides is presented, employing tosic anhydride as the activator and tetra-n-butylammonium bromide as the nucleophilic bromide source. The C2-brominated compounds are produced in moderate to excellent yields and with excellent regioselectivity in most cases. The potential extension of this method to other halogens, effecting C2-chlorination with Ts2O/TBACl is also presented. Finally, this method could be incorporated into a viable one-pot oxidation/bromination process, using methyltrioxorhenium/urea hydropgen peroxide as the oxidant.
- Wengryniuk, Sarah E.,Weickgenannt, Andreas,Reiher, Christopher,Strotman, Neil A.,Chen, Ke,Eastgate, Martin D.,Baran, Phil S.
-
supporting information
p. 792 - 795
(2013/04/10)
-
