An efficient synthesis of isoquinolines via rhodium-catalyzed direct C–H functionalization of arylhydrazines

Abstract

A highly efficient rhodium-catalyzed C-H activation of arylhydrazines and coupling with internal alkynes has been realized under mild conditions. The isoquinolines have been prepared in moderate to excellent yields in high efficiency. This methodology features the use of readily available starting materials, and a simple hydrazine moiety as a directing group, in the absence of an external metal co-oxidant under an air atmosphere. The C-H bond activation and the N-N bond cleavage have been successively realized under mild conditions.

Comprehensive Strategies for the Synthesis of Isoquinolines: Progress Since 2008

“…Deshmukh and Bhanage designed a Ru‐catalyzed N ‐tosylhydrazone 9 e directed annulation towards the synthesis of isoquinolines 74 h [260] . The method was similar to the previous reported method by Zhang et al [202] . in 2015 using Rh‐catalysis (Scheme 253).…”

“…Benzimidates and diazo compounds of different substitution were successfully converted into isoquinoline derivatives in good yields (Scheme 252). [259] Deshmukh and Bhanage designed a Ru-catalyzed N-tosylhydrazone 9 e directed annulation towards the synthesis of isoquinolines 74 h. [260] The method was similar to the previous reported method by Zhang et al [202] in 2015 using Rh-catalysis (Scheme 253).…”

“…Zhang et al describes the synthesis of isoquinolines 74 using aryl hydrazines 329 and internal alkynes 69 in presence of rhodium-catalyzed CÀ H activation (Scheme 197). [202] The method relies on using hydra- zines as readily available directing groups, in presence of catalytic amount of benzoic acid under rhodium catalyzed reaction conditions. The protocol has been realized under aerial atmospheric conditions to bring about CÀ H activation and NÀ N bond cleavage.…”

Synthesis of Isoquinoline Derivatives via Palladium‐Catalyzed C−H/C−N Bond Activation of N‐Acyl Hydrazones with α‐Substituted Vinyl Azides

“…Recently, transition-metal-catalyzed direct CÀ H functionalization has emerged as a novel strategy to construct isoquinoline skeleton by CÀ H/NÀ N bond activation or CÀ H/NÀ O bond activation with nitrogen-containing directing groups including aromatic hydrazines, imines, azines oximes, etc. [6][7][8][9] In most cases, internal nitrogen source of isoquinolines was also provided by directing groups.…”

The C–H Activation/Bidirecting Group Strategy for Selective Direct Synthesis of Diverse 1,1′-Biisoquinolines

“…Oximes are employed as oxidizing directing groups (DG ox ) without external oxidants and give H 2 O as the byproduct. For example, the synthesis of isoquinolines through DG ox -mediated annulation of aromatic oximes, imines, hydrazone, azines, and azides with alkynes using Rh, Ru, or Co as the catalyst has been well-developed. Glorius and Qi reported the Rh III -catalyzed C–H activation/1,3-diyne strategy to access 3,3′-biisoquinolines and 3,4′-biisoquinolines, respectively (Scheme a).…”