Dual NHC/photoredox catalytic synthesis of 1,4-diketones using an MR-TADF photocatalyst (DiKTa)

Abstract

The use of the recently reported organic multi-resonant thermally activated delayed fluorescence (MR-TADF) photocatalyst DiKTa allows for the modular synthesis of 1,4-diketones under mild and metal-free conditions. The reaction proceeds...

Recent advances in three-component radical acylative difunctionalization of unsaturated carbon–carbon bonds

“…Soon after, the Smith 117 group and Han 118 group disclosed a similar diacylation system (Scheme 43A and B). However, a reductive quenching mechanism of PC* by α-keto acid 43-3 was proposed for the generation of transient acyl radicals.…”

Radical Acylation of Alkenes by NHC‐Organocatalysis

“…In Zhang's work, the merge of NHC‐catalyst NHC‐14 and an Ir‐photocatalyst was designed for the diacylation of alkenes using aroyl fluorides and α‐keto acids as the acyl‐source (Scheme 34a) [48] . While in Smith's work, the combination of the same type of NHC‐catalyst NHC‐15 with an organo‐photocatalyst DiKTA allowed the modular synthesis of 1,4‐diketones using the identical acyl‐precursors under mild and metal‐free conditions (Scheme 34b) [49] . Differently, only aromatic conjugated alkenes were tolerated with Smith's reaction system.…”

“…[48] While in Smith's work, the combination of the same type of NHC-catalyst NHC-15 with an organo-photocatalyst DiKTA allowed the modular synthesis of 1,4-diketones using the identical acyl-precursors under mild and metal-free conditions (Scheme 34b). [49] Differently, only aromatic conjugated alkenes were tolerated with Smith's reaction system. Later after these two works, a dicarbonylation of styrenes with aryl fluorides and potassium 2-ethoxy-2oxoacetate via cooperative NHC/ photoredox catalysis was also achieved by Feng and co-workers (Scheme 34c).…”

Accelerating Intersystem Crossing in Multiresonance Thermally Activated Delayed Fluorescence Emitters via Long-Range Charge Transfer

“…Since the RISC might be in the region of 0.1–1.0 ms, we cannot directly see the enhanced RISC because of time-region limitation of our setups for lifetime measurements; it is expected that the enhanced spin–orbit coupling (SOC) between the singlet short-range charge transfer (SRCT) and triplet LRCT manifolds could also enhance the RISC process. For the MR-TADF materials, due to their long triplet lifetime, unobvious emission solvatochromism, large molar absorptivity, and low energy loss in emission in polar dielectric environments, the ability to tune the population ratio between singlet and triplet excitons could greatly extend their applications in triplet–triplet energy transfer (TTET) in host–guest systems , and photocatalyst systems. − The increased population ratio of the triplet exciton in the host materials or photosensitizers could be beneficial for the improvement of energy-transfer efficiency.…”