A novel approach for rhodium(iii)-catalyzed C–H functionalization of 2,2′-bipyridine derivatives with alkynes: a significant substituent effect

Abstract

A novel approach for rhodium(iii)-catalyzed C–H functionalization of 2,2′-bipyridine derivatives was developed, which elucidated significant substituent effects on the rollover cyclometalation.

Efficient Access to Isoquinolines via Rhodium-Catalyzed Oxidative Annulation of Pyridyl C–H Bonds Directed by Carbonyl with Internal Alkynes

“…Continuing our interest in the synthesis of functionalized heterocycles, 11 herein we report a new and efficient Rh-catalyzed [2+2+2] annulation of C-H bonds with internal alkynes, enabled by a directing carbonyl and steric hindrance of the 2-amino substituent of pyridine, to prepare 2aminoisoquinoline derivatives in moderate to good yields (Scheme 1, eq 4). Different from previous work, [6][7][8][9] herein the annulations are initiated by a six-membered rhodacycle in situ generated from coordination with the directing group and metalation with ortho C-H activation.…”

“…2,2-bipyridine could weaken the adjacent N-Rh bond and promote rollover cyclometalation and C-H functionalization (Scheme 1, eq 3). 9 In these previous works, the annulations are initiated by in situ generation of five-membered rhodacyclic intermediates.…”

Rollover Cyclometalation as a Valuable Tool for Regioselective C–H Bond Activation and Functionalization

“…The same strategy ([RhCp*Cl2]2 as catalyst, heating in the presence of AgOAc and a base) was adopted for 2,2′-bipyridine functionalization. Experimental and DFT data showed a considerable substituent effect: as often observed for substituted 2,2′-bipyridines, a substituent in position 6 plays an important role, weakening the nearby Rh–N bond and facilitating subsequent rollover C–H bond activation and functionalization [ 148 ].…”

Synthesis of 2,2’‐Bipyridines through Catalytic C−C Bond Formations from C−H Bonds

“…In 2020, Chen, Liu, Zhu, and co‐workers developed a novel approach for the C−H functionalization of 2,2’‐bipyridine derivatives through a rollover cyclometalation pathway (Scheme 18). [38] The substituent at the C6 position of 2,2’‐bipyridine weakened the adjacent N−Rh bond promoting the rollover cyclometalation, C−H activation, and functionalization sequence. The pyridine ring of 2,2’‐bipyridine holding the C6 substituent was annulated via an oxidative double C−H bond alkenylation using 5 mol % [Cp*RhCl 2 ] 2 , in the presence of 2.5 equivalents of AgOAc and 5.0 equivalents of NaOAc in 1,2‐dichloroethane (DCE) at 110 °C.…”