A general, simple catalyst for enantiospecific cross couplings of benzylic ammonium triflates and boronic acids: no phosphine ligand required
作者:Danielle M. Shacklady-McAtee、Kelsey M. Roberts、Corey H. Basch、Ye-Geun Song、Mary P. Watson
DOI:10.1016/j.tet.2014.03.039
日期:2014.7
enantiospecific crosscoupling of benzylic ammonium triflates with boronic acids are reported. This method relies on the use of Ni(cod)2 without ancillary phosphine or N-heterocyclic carbene ligands as catalyst. These conditions enable the coupling of new classes of boronic acids and benzylic ammonium triflates. In particular, both heteroaromatic and vinyl boronic acids are well tolerated as coupling partners
and/or alkyllithium species reacted smoothly with aryl and/or benzyl ethers with cleavage of the inert C−O bond to afford cross‐coupled products, catalyzed by commercially available [Ni(cod)2] (cod=1,5‐cyclooctadiene) catalysts with N‐heterocyclic carbene (NHC) ligands. Furthermore, the couplingreaction between the aryllithium compounds and aryl ammonium salts proceeded under mild conditions with C−N
Chirality sensing of choline derivatives is achieved by a self-assembled, racemic triple anion helicate cage which exhibits induced circular dichroism (ICD) upon encapsulation of a chiral guest. The host–guestinteractions were illustrated by NMR, crystal structure, CD and DFT calculations. The absolute configurations and ee values were determined by ICD.
We report a chiral deep cavitand receptor based on calix[5]arene stabilized by a cooperative network of hydrogen bonds and having a highly flexible structure. The cavitand displays enantioselective molecular recognition with a series of chiral quaternary ammonium salts, providing unprecedented stability ratios between the corresponding diastereomeric host–guest complexes. Molecular dynamics simulations