Cobalt-catalyzed enantioselective C–H/N–H annulation of aryl sulfonamides with allenes or alkynes: facile access to C–N axially chiral sultams

Abstract

Herein we report a cobalt-catalyzed enantioselective C-H/N-H annulation of aryl sulfonamides with allenes and alkynes, using either chemical or electrochemical oxidation. By using O2 as the oxdiant, the annulation with...

Cobalt-catalyzed atroposelective C−H activation/annulation to access N−N axially chiral frameworks

“…It was pleased to find that the desired N–N axially chiral isoquinolinone product 3aa was obtained with 48% yield and excellent 99% ee, with L6 bearing bulky tert -butyl groups at the ortho - and para -position of phenol as the chiral ligand. And this promoting effect of the bulky t Bu-Salox ligand has also been reported in the previous Co/Salox catalysis developed by Shi 69 , Ackermann 56 and our group 73 . Various cobalt catalysts, such as Co(OAc) 2 , and Co(OBz) 2 , CoCl 2 ·6H 2 O, were fully investigated, in which no better results have got (entries 1–4, and Supplementary Table 2 ).…”

“…For this purpose, asymmetric C–H functionalization, as a timely emerged and well-established tactic, was built up to form diverse charming structures containing highly functionalized skeletons, such as natural products, pharmaceutical lead compounds, important architectures which typically takes advantage of batch production with satisfactory chemical selectivity (stereoelectronic selectivity and regioselectivity) via transition metal catalyzed process 40 – 45 . In this content, the first-row 3d-metal cobalt-catalyzed C–H functionalization has gained increasing popularity owing to its earth-abundance, low toxicity, and distinctive reactivities 46 – 53 , which has been largely developed for the synthesis of various skeletons by Ackermann 54 – 56 , Yoshino and Matsunaga 57 – 60 , Cramer 61 – 63 , Shi 64 – 69 , and our groups 70 – 73 . Very recently, our group 70 , and Shi’s group 65 independently developed an efficient chiral Co/Salox (salicyl-oxazoline) system, and demonstrated its excellent reactivity for assembling C–N and C–C axially chiral compounds.…”

Enantioselective C–H bond functionalization under Co(iii)-catalysis

“…In 2023, Niu and co-workers reported a Co/salox ( L6 ) based catalytic system for C–H bond annulation of sulfonamides with allenes/alkynes with excellent enantiomeric excess and moderate-to-good yields (Scheme 15a). 68 The developed methodology was applied to access a variety of chiral sultams in one step ( 70 and 71 ). At the same time, they developed a C–N axially chiral hetero-biaryl isoquinolinone skeleton construction via cobalt-catalyzed atroposelective C–H activation/annulation of benzamides and allenes with excellent yields and enantiomeric excess under thermal conditions (Scheme 15b).…”

The crucial role of silver(i)-salts as additives in C–H activation reactions: overall analysis of their versatility and applicability

“…Another convenient approach for silver-additive free C–H activation is the use of a preactivated electrophilic catalyst consisting of ligands that are labile enough to facilitate the interaction between the substrate and the metal centre, 73 which was well exemplified by the work by Nan and co-workers. 73 a They delineated a successful rhodium-catalyzed C–H annulation of anilines for the formation of quinoline derivatives in moderate to good yields ( Scheme 23 ).…”