The Merger of Photoredox and Cobalt Catalysis

Emerging concepts in photocatalytic organic synthesis

“…Key to the success is the modulation of the oxidation state of transition metal complexes by SET processes, radical additions, or photosensitization. This strategy is extensively studied using nickel complexes ( Milligan et al., 2019 ; Twilton et al., 2017 ) and was further expanded to a range of other transition metals ( Hopkinson et al., 2014 ; Skubi et al., 2016 ), including abundant first row metals such as cobalt ( Kojima and Matsunaga, 2020 ), copper ( Hossain et al., 2019 ), and iron ( Neumeier et al., 2020 ; Ouyang et al., 2019 ). Combining photo- and organocatalysis involves SET of an excited PC and, for example, enamine intermediates to enable the α-functionalization of aldehydes with high enantioselectivity ( Nicewicz and MacMillan, 2008 ).…”

Hydroxyl Assisted, Photoredox/Cobalt Co‐catalyzed Semi‐Hydrogenation and Tandem Cyclization of o‐Alkynylphenols for Access to 2,3‐Dihydrobenzofurans

“…As shown in scheme 1A, the active low‐valent Co I or cobalt hydride (Co−H) species could generate feasibly in situ by the reduction of high‐valent cobalt precursors in the presence of electron donor reagent. Nowadays, extensive studies have been conducted in dehydrogenative reactions by using this strategy, in which Co−H reacted with proton to release hydrogen is the key procedure [3a–c,4] . On the other hand, Co−H mediated hydrocarbonation of alkenes represents another important reaction pattern in photoredox/cobalt dual catalysis (Scheme 1Aa).…”

Microwave-Assisted Synthesis of Quinazolines and Quinazolinones: An Overview

“…Although the aforementioned reactions are considered as the most important transition-metal catalyses, a plethora of vital reactions can be effectively catalyzed by various transition metals including reductive elimination, oxidative addition, and transmetallation. Transition metal catalysis has also found extensive applications in the convenient and efficient synthesis of a wide variety of heterocyclic systems (Ma et al, 2017 ; Ramanathan and Liu, 2017 ; Tiwari and Bhanage, 2017 ; Chatterjee et al, 2018 ; Saikia et al, 2018 ; Chen et al, 2020 ; Debabrata et al, 2020 ; Ghosh et al, 2020 ; Janardhanan et al, 2020 ; Jiang et al, 2020 ; Kanwal et al, 2020 ; Kojima and Matsunaga, 2020 ; Li and Zhang, 2020 ; Nagata and Obora, 2020 ; Neto and Zeni, 2020a , b ; Pal et al, 2020 ; Ratmanova et al, 2020 ; Sahiba and Agarwal, 2020 ; Sonawane et al, 2020 ; Xuan et al, 2020 ). However, the literature survey revealed only an example of zinc (Shi et al, 2004 ), a limited number of iron-catalyzed (Melvin et al, 1992 ; Valderrama et al, 1999 ; Kanth et al, 2006 ; Yin et al, 2012 ; Gopalaiah et al, 2017 , 2019 ; Raut and Bhanage, 2017 ; Eidi et al, 2018 ), and relatively more copper-catalyzed reactions, leading to the synthesis of quinazoline and quinazolinone derivatives (Melvin et al, 1992 ; Chatterjee et al, 2018 ; Potuganti et al, 2018 ; Liang et al, 2019 ; Rodrigues et al, 2019 ; Donthiboina et al, 2020 ).…”