Nitrene Transfer Catalysis by S-Chelated Metal Complexes

Abstract

Metal-catalyzed nitrene transfer in green catalysis is an important type of reactions in organic transformations [1]. There have been numerous studies on nitrene transfer reactions including alkene aziridination and sulfide sulfimidation catalyzed by transition metal complexes with N- and/or O-chelating ligands using a variety of nitrene sources. We previously performed extensive investigation on metalloporphyrin catalysts for nitrene transfer reactions, including mechanistic studies [2]. In our endeavor to develop new types of biocompatible metal catalysts for nitrene transfer reactions, we found that cuboidal iron-sulfur clusters, which resemble the Fe4S4 or MFe3S4 active sites in biological systems [3], can catalyze aziridination of alkenes and sulfimidation of sulfides. These metal-sulfur clusters can be considered as metal complexes of inorganic Fe3S4 tridentate S-chelating ligands, which inspired our interest in exploring the catalytic behavior of related metal complexes bearing multidentate S-ligands with the metal ion adopting a coordination number and/or configuration similar or identical to that in native metal-sulfur clusters such as those in the active site of aconitase [4]. In this work, we present our findings obtained by examination of the catalytic behavior of the complexes of the first-row transition metal ions with multidentate S-donor chelating ligands including the scorpionate S3 ligands that have been extensively used in coordination chemistry [5] yet unemployed for nitrene transfer catalysis. A series of such metal complexes have been prepared and structurally characterized, some of which, such as Cu(I) complexes with tris(mercaptoimidazoyl)borates, have been found to be highly active catalysts for nitrene transfer reactions, including aziridination of alkenes and sulfimidation of sulfides, affording aziridines and sulfimides in high-to-excellent yields (up to 99%) with low catalyst loading (1 mol%) at room temperature. References [1] a) A. Fingerhut, O. V. Serdyuk, S. B. Tsogoeva, Green Chem. 2015, 17, 2042-2058; b) V. Bizet, C. M. M. Hendriks, C. Bolm, Chem. Soc. Rev. 2015, 44, 3378-3390; c) L. Degennaro, P. Trinchera, R. Luisi, Chem. Rev. 2014, 114, 7881-7929; d) H. Pellissier, Adv. Synth. Catal. 2014, 356, 1899-1935; e) N. Jung, S. Bräse, Angew. Chem. 2012, 124, 5632–5634; Angew. Chem. Int. Ed. 2012, 51, 5538-5540. [2] a) S. K.-Y. Leung, W.-M. Tsui, J.-S. Huag, C.-M. Che, J.-L. Liang, N. Zhu, J. Am. Chem. Soc. 2005, 127, 16629-16640; b) J.-L. Liang, J.-S. Huang, X.-Q. Yu, N. Zhu, C.-M. Che, Chem. Eur. J. 2002, 8, 1563-1572. [3] a) S. C. Lee, W. Lo, R. H. Holm, Chem. Rev. 2014, 114, 3579-3600; b) H. Beinert, R.H. Holm, E. Münck, Science 1997, 277, 653-659. [4] H. Beinert, M. C. Kennedy, C. D. Stout, Chem. Rev. 1996, 96, 2335-2373. [5] M. D. Spicer, J. Reglinski, Eur. J. Inorg. Chem. 2009, 1553-1574.