Selective Intramolecular CH Amination through the Metalloradical Activation of Azides: Synthesis of 1,3‐Diamines under Neutral and Nonoxidative Conditions

Abstract

Amino groups exist ubiquitously in natural products and synthetic molecules, and play key roles in a wide range of important applications. Consequently, immense effort has been devoted to the development of efficient and selective processes for the preparation of amines. [1] Among different approaches, the catalytic amination of abundant C À H bonds on the basis of a metal-mediated nitrene-insertion pathway is one of the most general and direct methods for installing nitrogen functionalities. [2] The promise of this approach as a synthetically useful methodology has been demonstrated with a number of intramolecular C À H amination processes through the combined use of Rh II 2 -based catalysts and iminoiodane nitrene sources. [2,3] Notably, Du Bois and coworkers elegantly demonstrated that N-Boc-protected sulfamides could be selectively converted into cyclic sulfamides by [Rh 2 (esp) 2 ] in combination with PhI(OAc) 2 and MgO to provide access to synthetically useful 1,3-diamines (esp = a,a,a',a'-tetramethyl-1,3-benzenedipropionate). [4] The Rh II 2based intramolecular amination was shown to be effective for both secondary and tertiary CÀH bonds with stereospecificity and high diastereoselectivity. However, the amination of strong primary CÀH bonds had yet to be demonstrated. [5] Moreover, the catalytic system was unsuitable for simple Nalkyl sulfamides, which were oxidatively degraded by the stoichiometric oxidant, PhI(OAc) 2 . [4] As stable metalloradicals, cobalt(II) complexes of porphyrins, [Co(Por)], have emerged as a new class of catalysts for CÀH amination. [6] The cobalt(II)-based metalloradical amination (MRAm) is different from the commonly studied Rh 2 system, as it can operate effectively with various azide substrates without the need for terminal oxidants and other additives. [7][8][9][10][11] To further validate the utility of C À H amination methodology based on a cobalt(II) catalyst and azides, we envisioned a general strategy for the synthesis of 1,3-diamines from monoamines through the key step of the intramolecular C À H amination of sulfamoyl azides with [Co(Por)] (Scheme 1). We report herein a cobalt(II)-based catalytic system that is highly effective for the intramolecular 1,6-CÀH amination of sulfamoyl azides to furnish six-membered cyclic sulfamides. Not only excellent regioselectivity, but also high diastereoselectivity and stereospecificity were observed with the catalytic system. The cobalt(II)-catalyzed amination is operationally simple, as it proceeds under neutral and nonoxidative conditions without the need for other reagents, and N 2 is the only byproduct. Consequently, the degree of functional-group tolerance is high, and the reaction can be applied to substrates with various substituents, such as oxidizable amide and sulfide groups. An important feature of this catalytic system is the effective amination of strong primary C À H bonds, as well as secondary and tertiary C À H bonds.A wide range of sulfamoyl azides 2 were conveniently prepared from the corresponding amines 1 on the ...

Chemoselective single-site Earth-abundant metal catalysts at metal–organic framework nodes

“…Developing iron catalysts for sp 3 C–H amination is of particular interest due to the high abundance and low toxicity of iron484950. Although most Fe-catalysed C–H amination reactions use sulfamides or azides as a nitrogen source4546485051, we report here the first example of using aniline as a nitrogen source. Heating aniline with neat substrates such as indane, tetraline and cyclohexene gave a C–H aminated product in 41–53% yield with UiO-FeBr (2–10 mol% Fe, Table 4 and Supplementary Fig.…”

“…We studied the catalytic activity of UiO-FeBr in C–H amination reactions because the conversion of C–H bonds to C–N bonds provides a valuable method for introducing nitrogen functionalities directly into a molecule44454647. Developing iron catalysts for sp 3 C–H amination is of particular interest due to the high abundance and low toxicity of iron484950.…”

Selective CCsp Bond Cleavage: The Nitrogenation of Alkynes to Amides

“…Herein, we report the first direct C sp 2 À C sp bond functionalization of alkynes through a nitrogenation process to amides, which is one of the most important organic functional groups in natural products and pharmaceuticals [8] (Scheme 1 b). Initially, we examined the transformation of 1,2-diphenylethyne (1 a) to N,2-diphenylacetamide (2 a) in the presence of TFA and TMSN 3 , as a nitrogen source, [9] in DCE ( [c] [PPh 3 AuCl]/Ag 2 CO 3 TFA DCE 72 17 [c,d] [PPh 3 AuCl]/Ag 2 CO 3 TFA DCE 89 18 [c] [XPhosAuCl]/Ag 2 CO 3 TFA DCE 43 19 [c] [JohnPhosAuCl]/Ag 2 CO 3 TFA DCE 35 20 [c] [IPrAuCl]/Ag 2 CO 3 TFA DCE 52 21 [c] [IMesAuCl]/Ag 2 CO 3 TFA DCE 41 22 [c] [ …”

The Use of Cobalt‐Mediated Cycloisomerisation of Ynedinitriles in the Synthesis of Pyridazinohelicenes

“…It generates the valence tautomeric Co III complex C, [19] which as a carbon-centred radical undergoes the cascade radical cyclisation C!D!E closing two carbocycles. Upon forming the Co III intermediate E (a nitrogen-centred radical), this species undergoes intramolecular homolytic substitution reaction (S H i) [20] on nitrogen being accompanied by the (now reversed) single-electron transfer from the ylideneazanide ligand to the Co III centre. It finalises the pyridazine ring closure by connecting nitrogen atoms.…”