A Highly Efficient and Selective Aerobic Cross‐Dehydrogenative‐Coupling Reaction Photocatalyzed by a Platinum(II) Terpyridyl Complex

Abstract

Thanks to the superior redox potential of platinum(II) complex compared with that of Ru(bpy)3(2+) in the excited state, an efficient and selective visible-light-induced CDC reaction has been developed by using a catalytic amount (0.25 %) of 1. With the aid of FeSO4 (2 equiv), the corresponding amide could not be detected under visible-light irradiation (λ=450 nm), but the desired cross-coupling product was exclusively obtained under ambient air conditions. A spectroscopic study and product analysis revealed that the CDC reaction is initiated by photoinduced electron-transfer from N-phenyltetrahydroisoquinoline to the complex. An EPR (electron paramagnetic resonance) experiment provides direct evidence on the generation of superoxide radical anion (O2(-·)) rather than singlet oxygen ((1)O2) under irradiation of the reaction system, in contrast to that reported in the literature. Combined, the photoinduced electron-transfer and subsequent formation of superoxide radical anion (O2(-·)) results in a clean and facile transformation.

A Hydrazone‐Based Covalent Organic Framework as an Efficient and Reusable Photocatalyst for the Cross‐Dehydrogenative Coupling Reaction of N‐Aryltetrahydroisoquinolines

“…Recently, Stephenson and co‐workers demonstrated an efficient method for the visible‐light‐mediated photocatalytic aza‐Henry reaction of nitromethane with N ‐aryltetrahydroisoquinolines (THIQs) using air as terminal oxidant . Considerable efforts have been devoted to this area, and the aza‐Henry reaction of THIQ derivatives represents one of the most exploited photocatalytic transformations with a variety of photocatalysts, such as iridium, platinum, ruthenium, organic dyes, TiO 2 , CdS, metal–organic frameworks, and porous organic polymers . Despite these impressive advances, it remains a great challenge to explore new photocatalytic systems that are highly stable and highly active in catalyzing visible‐light‐driven organic transformations with high efficiency, low cost, and minimum environmental impact and energy consumption.…”

“…[3] Recently,S tephenson and co-workers demonstrateda ne fficient methodf or the visible-light-mediated photocatalytic aza-Henry reactiono fn itromethane with N-aryltetrahydroisoquinolines (THIQs) using air as terminal oxidant. [4] Considerable efforts have been devotedt ot his area, and the aza-Henry reactiono f THIQ derivatives represents one of the most exploited photocatalytic transformationsw ith av ariety of photocatalysts, such as iridium, [5] platinum, [6] ruthenium, [7] organicd yes, [8] TiO 2 , [9] CdS, [10] metal-organic frameworks, [11] and porous organic polymers. [12] Despite these impressive advances, it remains ag reat challenge to explore new photocatalytics ystems that are highly stablea nd highly active in catalyzing visible-light-driven organic transformationsw ith high efficiency,l ow cost, and minimum environmental impact and energy consumption.T o achieve efficient and environmentally benign photocatalytic transformations, it is important to develop heterogeneous catalytic systems that not only utilize the available energies to photochemically activate organic substrates for desired synthetic transformationsb ut are also easily recovered and reused in photocatalytic reactions.…”

Visible‐Light‐Driven C−H Oxidation of Cyclic Tertiary Amines: Access to Synthetic Strychnos Alkaloids with Antiviral Activity

“…Superoxide radical anion (O 2 .− ), formed during regeneration of RB .− by back electron transfer (BET) to molecular oxygen, can react with radical cation B to form α‐amino radical C (path 1). This deprotonation step is mediated by NaOAc, used as a base additive.…”

Merging Visible‐Light Photocatalysis and Palladium Catalysis for C−H Acylation of Azo‐ and Azoxybenzenes with α‐Keto Acids

“…To support the generation of superoxide radical anion C (O 2 − ⋅) in proposed mechanism, 5,5‐dimethyl‐1‐pyrroline‐ N ‐oxide (DMPO) was used as a probe to capture the active species ,. As shown in Figure , when a toluene solution of DMPO, 2 a , and PC‐ A was without the blue LED irradiation, no signal was detected (Figure a).…”