Cyclometalated iridium complexes are shown to be excellent catalysts for transferhydrogenation of carbonyl compounds in water using formate as a hydrogen source. A wide range of ketones and aldehydes have been reduced at 0.05% catalyst loading with no need for any organic solvents. Solution pH is found to play a critical role, with acidic conditions needed for fasttransferhydrogenation.
Reductive amination of various ketones and aldehydes by transferhydrogenation under aqueous conditions has been developed, by using cyclometallated iridium complexes as catalysts and formate as hydrogen source. The pH value of the solution is shown to be critical for a high catalytic chemoselectivity and activity, with the best pH value being 4.8. In comparison with that in organic solvents, the reductive
Pd(II)/Bu4NBr/DMSO Catalytic System for Practical Synthesis of Indoles and Pyrroles from Imines through Aerobic Dehydrogenative Cyclization
作者:Naohiko Yoshikai、Wei Tan、Xiaoya Hou
DOI:10.1055/s-0034-1379208
日期:——
scales (up to 55 mmol). N-Aryl- and N-allylimines derived typically from substituted acetophenones undergo palladium(II)-catalyzeddehydrogenativecyclization reactions in the presence of tetrabutylammonium bromide and molecular oxygen in DMSO to afford indole and pyrrole derivatives, respectively, in moderate to good yields. The reactions are operationally simple and can be readily performed on multigram
Levulinic acid (LA) is transformed into pyrrolidinones via iridium-catalysed reductive amination using formic acid as the hydrogen source under aqueous conditions. The catalytic system is the most active and performs under the mildest conditions ever reported for the reductive amination of LA.
Palladium-Catalyzed Aerobic Oxidative Cyclization of <i>N</i>-Aryl Imines: Indole Synthesis from Anilines and Ketones
作者:Ye Wei、Indubhusan Deb、Naohiko Yoshikai
DOI:10.1021/ja3030824
日期:2012.6.6
We report here an operationally simple, palladium-catalyzed cyclization reaction of N-aryl imines, affording indoles via the oxidative linkage of two C-H bonds under mild conditions using molecular oxygen as the sole oxidant. The process allows quick and atom-economical assembly of indole rings from inexpensive and readily available anilines and ketones and tolerates a broad range of functional groups