Catalyst shuttling enabled by a thermoresponsive polymeric ligand: facilitating efficient cross-couplings with continuously recyclable ppm levels of palladium
作者:Erfei Wang、Mao Chen
DOI:10.1039/c9sc02171j
日期:——
A polymeric monophosphine ligand WePhos has been synthesized and complexed with palladium(II) acetate [Pd(OAc)2] to generate a thermoresponsive pre-catalyst that can shuttle between water and organic phases, with the change being regulated by temperature. The structure of the polymeric ligand was confirmed with matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry
A Micellar Catalysis Strategy for Suzuki–Miyaura Cross-Couplings of 2-Pyridyl MIDA Boronates: <i>No Copper</i>, in Water, Very Mild Conditions
作者:Nicholas A. Isley、Ye Wang、Fabrice Gallou、Sachin Handa、Donald H. Aue、Bruce H. Lipshutz
DOI:10.1021/acscatal.7b03241
日期:2017.12.1
Suzuki-Miyaura (SM) cross-couplings of 2-pyridyl MIDA boronates can be successfully carried out in the complete absence of copper by attenuation of the Lewis basicity associated with the pyridyl nitrogen using selected substituents (e.g., fluorine or chlorine) on the ring. This strategy imparts additional synthetic options compared with existing approaches based on the use of Lewis acids or N-oxides. Thus, access to highly valued 2-substituted pyridyl rings via an initial Suzuki-Miyaura coupling can be followed by dehalogenation, SNAr reactions, or a second SM coupling to arrive at 2,6-disubstituted pyridyl arrays, all run in a single pot, enabled by micellar catalysis in water. Accessing targets within drug-like space is demonstrated in a four-step, one-pot sequence. Computational data suggest that the major role being played by electron-withdrawing substituents in promoting these cross-couplings without the need for copper is to slow the rates of protodeboronation of intermediate 2-pyridylboronic acids.
Perylenequinonoid-catalyzed photoredox activation for the direct arylation of (het)arenes with sunlight
and photobiology. However, their applications in photocatalysis are yet to be explored. We report here that sunlight along with 1 mol% cercosporin, which is one of the perylenequinonoid pigments, catalyzes the direct C–H bond arylation of (het)arenes by a photoredox process with good regioselectivity and broad functional group compatibility. Furthermore, a gram-scale reaction with great conversions