Abstract
Abstract 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.
Highlights
Nitrogen-containing motifs are found in a variety of synthetically [1], biologically [2] and pharmaceutically [3]relevant molecules
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 ligand design was varied regarding different aspects, and three novel bis(pyrazolyl)methane ligands were prepared which have different chiral pyrazolyl units or substituents on the pyridinyl group, with the chiral pyrazolyl units based on pulegone and camphor
Summary
Nitrogen-containing motifs are found in a variety of synthetically [1], biologically [2] and pharmaceutically [3]. The Ray group reported stable copper nitrene complexes coordinated by neutral amine ligands These can be stabilized by incorporation into an azamacrocycle [58] or by the addition of scandium(III) triflate [59, 60]. The phosphonitrene can coordinate in different stoichiometries and forms a μ-nitrene-bridged, a terminal nitrene and a twofold coordinated species [62] In contrast to those singlet copper nitrene complexes, the Betley group reported a terminal copper nitrene complex in the triplet state stabilized by. Our group presented a series of terminal singlet bis(pyrazolyl)methane copper nitrene complexes. These nitrene complexes were stabilized and characterized at low temperature. This includes a tyrosinase-like catalytic phenol hydroxylation [67,68,69,70], the oxidation of benzylalcohols with modified microgels [71], a palladium-free Sonogashira cross coupling [72, 73] and the asymmetric cyclopropanation of styrene [74,75,76]
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