Room-temperature C–H bond alkynylation by merging cobalt and photocatalysts

Abstract

A new protocol is developed for the mono and bis-ortho-C-H alkynylation of easily accessible benzamide derivatives using alkynyl bromides at room temperature merging cobalt and photo redox catalysis. The diverse...

Dual Photoredox and Cobalt Catalysis Enabled Transformations

“…To begin with, Simultaneously, Sundararaju and coworkers realized the CÀ H alkynylation of benzamide derivatives with alkynyl bromides via dual photoredox and cobalt catalytic system (Scheme 20). [40] Formation of both Mono and bis alkynylation product was controlled by varying the stoichiometry of base and alkynyl bromide. In the case of linear alkynyl bromides annulated product was observed with complete regioselectivity.…”

Dual Metallaphotoredox‐Catalyzed Directed C(sp2)−H Functionalization: Access to C−C/C‐Heteroatom Bonds

“…In case of substituted allenes, the reaction regioslectively took place at the terminal position of the allene. Notably, in case of phenylallenes, exo-isoquinolinones formed exclusively in [43] In presence of Co(II), Na 2 eosin-Y as a photocatalyst and a stoichiometric NaOPiv as an additive, the annulated isoquinolones 56 formed with excellent regioselectivity. The said methodology supported functionally diverse benzamides and non-bulkier alkynyl bromides in delivering the desired products in moderate to good yields.…”

“…More recently, Sundararaju group accomplished a concise method for C−H/N−H bond annulation of benzamides with alkynyl bromides 55 (Scheme 27). [43] In presence of Co(II), Na 2 eosin‐Y as a photocatalyst and a stoichiometric NaOPiv as an additive, the annulated isoquinolones 56 formed with excellent regioselectivity. The said methodology supported functionally diverse benzamides and non‐bulkier alkynyl bromides in delivering the desired products in moderate to good yields.…”

Micro-photo-flow reactor system for fused N-heteroaryl scaffold synthesis and late-stage functionalization of pyrazolopyridines

“…Thus, the design of an alternative approach seemed relevant to address the limitations incurred in the previous processes. The most attractive alternative approach was to synthesize a fused N-hetero aryl scaffold through a photo-induced (4+2) annulation 9 and were further developed by . 10 Unfortunately, these reactions had some inherent limitations since they were achieved only in the presence of the PC.…”

“…The most attractive alternative approach was to synthesize a fused N-hetero aryl scaffold through a photo-induced (4+2) annulation reaction in the presence of visible light without using any oxidant and/or heat energy. 7 In the previous works, batch process annulation reactions mediated by an expensive photocatalyst (PC) have been reported by Rueping et al (2019), 7 b Xia et al (2020), 8 Sundararaju et al (2021) 9 and were further developed by Liu et al (2021). 10…”