Chemo‐ and Enantioselective Intramolecular Silver‐Catalyzed Aziridinations
作者:Minsoo Ju、Cale D. Weatherly、Ilia A. Guzei、Jennifer M. Schomaker
DOI:10.1002/anie.201704786
日期:2017.8.7
nitrene-transfer reactions are a powerful tool for the preparation of enantioenriched amine building blocks. Reported herein are chemo- and enantioselective silver-catalyzed aminations which transform di- and trisubstituted homoallylic carbamates into [4.1.0]-carbamate-tethered aziridines in good yields and with ee values of up to 92 %. The effects of the substrate, silver counteranion, ligand, solvent, and
The present invention provides fungicidal 4-substituted-3-phenyl[(heterocyclylmethoxy)imino]methyl}-1,2,4-oxadiazol-5(4H)-one derivatives of formula (I)
wherein A represents a pyridyl or thiazole group and X1, Y1 to Y5 represent independently different substituents.
Solvent Effects on the Chemo‐ and Site‐Selectivity of Transition Metal‐Catalyzed Nitrene Transfer Reactions: Alternatives to Chlorinated Solvents**
作者:Robert M. Ward、Yun Hu、Noah P. Tu、Jennifer M. Schomaker
DOI:10.1002/cssc.202300964
日期:2024.1.8
A high-throughput experimentation protocol for heterogeneous nitrene transfer (NT) reactions was used to identify replacements for chlorinated solvents. Selected catalysts for NT, including silver supported by N-dentate ligands, dinuclear Rh complexes and Fe/Mn phthalocyanine catalysts, were compared and contrasted using our HTE protocol in terms of both yields and selectivity.
Catalyst-Controlled Nitrene Transfer by Tuning Metal:Ligand Ratios: Insight into the Mechanisms of Chemoselectivity
作者:Cale Weatherly、Juliet M. Alderson、John F. Berry、Jason E. Hein、Jennifer M. Schomaker
DOI:10.1021/acs.organomet.7b00190
日期:2017.4.24
Catalyst.controlled, selective nitrene transfer is often challenging when both C-H and C=C bonds are present in a substrate. Interestingly, a simple change in the Ag(I):L ratio (L = bidentate N,N-donor ligand) enables tunable, chemoselective nitrene transfer that favors either C= C bond aziridination using an similar to 1:1 Ag:L ratio (AgLOTf) or insertion into a C-H bond when the Ag:L ratio in the catalyst is 1:2 (AgL2OTO. In this paper, mechanistic studies, coupled with kinetic profiling of the entire reaction course, are employed to examine the reasons for this unusual behavior. Steady-state kinetics were found to be similar for both AgLOTf and AgL2OTf; both complexes yield electronically similar reactive intermediates that engage in nitrene transfer involving formation of a short-lived radical intermediate and barrierless radical recombination. Taken together,, experimental and computational studies point to two effects that control tunable: cherrioSelectiVity: suppression of aziridination as the steric congestion around the silver center is increased in AgL2OTf and a decrease in the rate of C-H insertion with AgLOTf in comparison to AgL2OTE The observation that the sterics of Ag catalysts can be varied, with minor effects on the electronic features of the putative nitrene, has important implications for the development of other silver catalysts that enable tunable, site-selective C-H bond aminations..