Rhodium(III)-Catalyzed Oxidative Annulation of 2,2′-Bipyridine N-Oxides with Alkynes via Dual C–H Bond Activation

Abstract

Rh(III)-catalyzed switchable annulation of 2,2'-bipyridine N-oxides with internal alkynes via dual C-H bond activation has been developed. Tuning the reaction conditions enabled the reaction pathway to be switched between rollover and nonrollover annulation, delivering 5,6-disubstituted-1,10-phenanthrolines and 5,6,7,8-tetrasubstituted-1-(pyridin-2-yl)isoquinoline 2-oxides in high yields, respectively. The procedures feature excellent regioselectivity, broad substrate scope, and high tolerance of functional groups. The synthetic utilities of these obtained products were demonstrated in the catalytic reactions.

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.…”

Comprehensive Strategies for the Synthesis of Isoquinolines: Progress Since 2008

“…The present protocol was successful in delivering the diversely substituted isoquinoline derivatives in good yields (Scheme 218). [230] In 2019, Albano et al have isoquinoline synthesis through a silylcarbocyclisation/desilylation approach using suitable tosylamides 372 and aryldimethylsilanes 373. The protocol rely on silylcarbocyclisation and carbon monoxide (230) insertion to access (Z)-4-((dimethyl(phenyl)silyl)methylene)-2-tosyl-1,2,3,4-tetrahydroisoquinolin-3-ol 374 in high yields (Scheme 219).…”

“…The present protocol was successful in delivering the diversely substituted isoquinoline derivatives in good yields (Scheme 218). [230] …”

Pyridoacridines in the 21st Century

“…In studies of rhodium‐catalysed reactions of pyridine N ‐oxides, a couple of examples produced extended pyrido[2,3‐ c ]acridines, as in structure 293 from 292 (Scheme ) …”