Efficient aziridination of olefins with chloramine-T using copper iodide in water

Synthesis of N-tosylaziridines from substituted alkenes via zirconooxaziridine catalysis

Herein we report the zirconooxaziridine promoted aziridination of alkenes using chloramine T as the quantitative source of N. The reaction works with high yields, diastereoselectivities and stereospecificity for a wide variety of substituted alkenes. A potential mechanism involving the formation of a zirconooxaziridine complex as the active catalyst has been proposed and initial mechanistic data would indicate that a highly associative mechanism is the predominant pathway for this transformation.

Chiral bis(pyrazolyl)methane copper(I) complexes and their application in nitrene transfer reactions

In this study, chiral bis(pyrazolyl)methane copper(I) acetonitrile complexes were applied to generate two novel terminal copper tosyl nitrene complexes with the nitrene generating agent SPhINTs in dichloromethane at low temperatures. The syntheses of the chiral bis(pyrazolyl)methane ligands are based on pulegone and camphor, members of the natural chiral pool. The chiral copper(I) acetonitrile complexes were applied as catalysts in the copper nitrene mediated aziridination reaction of different styrene derivatives and the C–H amination of various substrates. The reactions afforded good yields, but low enantiomeric excess under mild conditions. The nitrene species have been characterized with UV/Vis and EPR spectroscopy and the products of the decay by ESI mass spectrometry.

A new generation of terminal copper nitrenes and their application in aromatic C-H amination reactions

Copper nitrene complexes are highly reactive species and are known as intermediates in the copper catalyzed C-H amination. In this study, three novel copper tosyl nitrene complexes were synthesized at low temperatures, stabilized with heteroscorpionate ligands of the bis(pyrazolyl)methane family. The copper nitrenes were obtained by the reaction of a copper(i) acetonitrile complex with ^SPhINTs in dichloromethane. We show that the ligand design has a major influence on the catalytic activity and the thermal stability of the copper nitrene complex. Not only the choice of the third N donor, but also the substituent in the 5-position of the pyrazolyl moiety, have an impact on the stability. Furthermore, the novel copper nitrene complexes were used for catalytic aziridination of styrenes and C-H amination reactions of aromatic and aliphatic substrates under mild reaction conditions. Even challenging substrates like benzene and cyclohexane were aminated with good yields. The copper nitrene complexes were characterized using UV/Vis spectroscopy, low temperature Evans NMR spectroscopy, density functional theory, domain-based local pair natural orbital coupled cluster calculations (DLPNO-CCSD(T)) and cryo-UHR mass spectrometry.

Designed To React: Terminal Copper Nitrenes and Their Application in Catalytic C-H Aminations

Heteroscorpionate ligands of the bis(pyrazolyl)methane family have been applied in the stabilisation of terminal copper tosyl nitrenes. These species are highly active intermediates in the copper-catalysed direct C-H amination and nitrene transfer. Novel perfluoroalkyl-pyrazolyl- and pyridinyl-containing ligands were synthesized to coordinate to a reactive copper nitrene centre. Four distinct copper tosyl nitrenes were prepared at low temperatures by the reaction with SO₂ tBuPhINTs and copper(I) acetonitrile complexes. Their stoichiometric reactivity has been elucidated regarding the imination of phosphines and the aziridination of styrenes. The formation and thermal decay of the copper nitrenes were investigated by UV/Vis spectroscopy of the highly coloured species. Additionally, the compounds were studied by cryo-UHR-ESI mass spectrometry and DFT calculations. In addition, a mild catalytic procedure has been developed where the copper nitrene precursors enable the C-H amination of cyclohexane and toluene and the aziridination of styrenes.

Nitrene transfer reactions mediated by metallo-porphyrin complexes

Nitrene transfer reactions represent a useful methodology to synthesize in a few steps high added-value compounds used as organic intermediates. Herein, we describe the catalytic activity of metal porphyrin complexes in a wide range of reactions such as C-H hydrocarbon amination and olefin aziridination to synthesize nitrogen containing molecules. All the most important nitrene sources have been reviewed stressing the potentiality and limits of each one in the particular class of chemical transformation.