Rhodium‐Catalyzed CH Aminations

Abstract

The formation of CÀN bonds is an important transformation in organic synthesis, as the amine functionality is found in numerous natural products and plays a key role in many biologically active compounds [1]. Standard catalytic methods to produce CÀN bonds involve functional group manipulations, such as reductive amination of carbonyl compounds [2], addition of nucleophiles to imines [3], hydrogenation of enamides [4][5][6][7][8], hydroamination of olefins [9] or a CÀN coupling reaction [10,11]. Recently, the direct and selective introduction of a nitrogen atom into a CÀH bond via a metal nitrene intermediate has appeared as an attractive alternative approach for the formation of CÀN bonds [12][13][14][15][16][17][18][19][20][21][22][23][24].Copper-catalyzed decomposition of benzenesulfonyl azide in the presence of cyclohexene was the first reported evidence of a metal-catalyzed nitrene insertion reaction [25]. This seminal discovery was then followed by the pioneering work of Breslow and Gellman who introduced the use of iminoiodinanes as metal nitrene precursors as well as rhodium dimer complexes as catalysts [26,27]. They showed the formation of the corresponding benzosultam in 86% yield in the presence of rhodium (II) acetate dimer (Rh 2 (OAc) 4 ) via an intramolecular metal nitrene CÀH bond insertion reaction (Eq. (5.1)). 86% Rh 2 (OAc) 4 (5 mol%) MeCN, rt S N I Ph O O S NH O O ð5:1ÞM€ uller then intensively studied rhodium dimer complexes as catalysts for the intermolecular amination of alkanes using iminoiodinanes, typically PhI¼NTs and PhI¼NNs [28][29][30]. Good yields were obtained for amination of benzylic, allylic and tertiary CÀH bonds, which are the most reactive CÀH bonds towards metal nitrenes. For instance the amination of indane provided the corresponding benzylic amine in Catalyzed Carbon-Heteroatom Bond Formation. Edited

Direct Stereospecific Synthesis of Unprotected N-H and N-Me Aziridines from Olefins

“…This initial screen identified Rh 2 (OAc) 4 as a promising catalyst for vic-amino-oxyarylation of olefins. Further evaluation of dimeric rhodium dicarboxylate complexes (table S3) revealed that just 1 mol % loading of Du Bois' catalyst (33)(34)(35)(36) (2, Fig. 1) in acetonitrile (MeCN) leads to amino-oxyarylated styrenes 4a and 4b at room temperature in 56% and 75% isolated yields, respectively.…”

Optoelectronic Properties and Structural Effects of the Incremental Addition of Pyridyl Moieties on a Rhodium Dimer

“…The paddle-wheel motif formed by many metal dimers offers a very modular and rigid scaffold to build up larger architectures. Many metals (e.g., copper, molybdenum, and rhodium) form neutral, dimetallic assemblies with carboxylate ligands. − Among these complexes, rhodium tetracarboxylate dimers have been extensively developed for catalytic applications. − These rhodium dimers have also been used for supramolecular assemblies, using axial or equatorial linkers to form discrete or infinite structures. − Other families of ligands, such as amidines, can be used to form metal dimer assemblies. The amidine metal dimers show great stability and greater functionalization potential than the tetracarboxylate dimers, since moieties can be attached on both the central carbon and the nitrogen atoms. − The drawback to this is their limited catalytic activity, , although they have been shown to be photoactive to alkyl halide reduction and mixed amidinate and diimine dimers have also gathered interest as an all-in-one chromophore–catalyst system for hydrogen production .…”

Stereoselective Rhodium-Catalyzed Amination of Alkenes

“…Typical methods to create C–N bonds involved functional group manipulations . Novel methodologies to perform direct C–H amination or aziridination reactions of carbon frameworks have recently been described using metal-catalyzed nitrene transfer . Metal nitrenes can be generated from azides, haloamines, , or, most frequently, iminoiodinanes .…”