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.
complex presented higher reactivity in the transferhydrogenation (TH) of ketones in 2-propanol. Experimentally, it was established that both the benzimidazole and amine N–H proton played a vital role in the enhancement of the catalytic activity. Utilizing this system a wide range of aldehydes and ketones were reduced efficiently. Notably, the TH of several imines, as well as chemoselective reduction of
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.