Abstract:Small organic radicals are ubiquitous intermediates in photocatalysis and are used in organic synthesis to install functional groups and to tune electronic properties and pharmacokinetic parameters of the final molecule. Development of new methods to generate small organic radicals with added functionality can further extend the utility of photocatalysis for synthetic needs. Herein, we present a method to generate dichloromethyl radicals from chloroform using a heterogeneous potassium poly(heptazine imide) (K-… Show more
“… 8 The extreme of nitrogen introduction in a graphitic structure leads to carbon nitride (CN), a mid band gap semiconductor with the ideal formula C 3 N 4 , which has attracted much attention in the past decade, especially for photocatalysis and very recently also for optical and optoelectronic applications. 9 − 15 …”
We present an innovative method for the synthesis of boron carbon nitride thin film materials in a simple furnace setup, using commonly available solid precursors and relatively low temperature compared to previous attempts. The as-prepared structural and optical properties of thin films are tuned via the precursor content, leading to a sp 2 -conjugated boron nitride− carbon nitride mixed material, instead of the commonly reported boron nitride−graphene phase segregation, with tunable optical properties such as band gap and fluorescence.
“… 8 The extreme of nitrogen introduction in a graphitic structure leads to carbon nitride (CN), a mid band gap semiconductor with the ideal formula C 3 N 4 , which has attracted much attention in the past decade, especially for photocatalysis and very recently also for optical and optoelectronic applications. 9 − 15 …”
We present an innovative method for the synthesis of boron carbon nitride thin film materials in a simple furnace setup, using commonly available solid precursors and relatively low temperature compared to previous attempts. The as-prepared structural and optical properties of thin films are tuned via the precursor content, leading to a sp 2 -conjugated boron nitride− carbon nitride mixed material, instead of the commonly reported boron nitride−graphene phase segregation, with tunable optical properties such as band gap and fluorescence.
“…Visible light‐irradiated reactions always provide efficient and convenient methods towards complex structures. In 2020, Savateev developed a method to generate dichloromethyl radicals from chloroform using a heterogeneous potassium poly(heptazine imide) (K‐PHI) photocatalyst under visible light irradiation conditions [32] . The reaction was conducted between enones and chloroform, with triethanolamine (TEOA) as electron donor and K‐PHI as the photocatalyst under irradiation of blue LED to generate a variety of γ,γ‐dichloroketones in yields up to 89% (Scheme 26).…”
Section: Di‐ and Trichloromethylation Using Polyhalomethanes As The Pmentioning
Molecules with di‐ or trichloromethyl group are widely existed in natural products and man‐made structures that represent special activities in pharmaceuticals and agrochemicals. Besides, polychloromethyl‐containing compounds are also high valuable intermediates in organic synthesis and also can be used as functional materials. Therefore, significant efforts have been made toward the incorporation of polychloromethyl groups into certain structures. In this field, a variety of polychloromethyl reagents, such as CH2Cl2, HCCl3, CCl4, TMSCCl3, TMSCCl2H, etc. have been utilized as the di‐ or trichloromethyl sources toward polychloromethylated structures through radical, nucleophilic, and other reaction patterns. In this review, we summarized and discussed the recent achievements in the synthesis of polychloromethylated compounds, mainly focused on the employment of different polychloromethyl reagents. Most of the works we investigated were reported after 2010. Mechanism discussions and outlooks were also given.
“…Very recently, Savateev and co‐workers reported that chloroform, an inactive halide, could be used to generate a dichloromethyl radical using a heterogeneous potassium poly(heptazine imide) (K‐PHI) photocatalyst ( Figure ). [ 55 ] As a result, dichloromethylation of enones was developed. In terms of the mechanism, the reaction is initiated by photoexcited electron‐induced SET reduction of chloroform to dichloromethyl radical.…”
“…Dichloromethylation of enones by carbon nitride photocatalysis and flow photoreactor design used in this work. [ 55 ] Reproduced with permission. [ 55 ] Copyright 2020, Springer Nature.…”
Solar photocatalysis is emerging as an environment‐friendly and sustainable energy approach for the production of fine chemicals and pharmaceuticals with high industrial and academic importance. Due to photochemical stability, tunable redox capability, and facile recyclability, semiconductor photocatalysts display remarkable advantages over molecular photocatalysts, thus attracting increasing attention. More importantly, photoexcited hole–electron pairs on semiconductor photocatalysts can accomplish two aligned redox reactions on the same semiconductor surface, resulting in unique designs of several semiconductor photocatalysis models. This review surveys recent advances in rational harnessing of photoexcited hole–electron pairs in semiconductor photocatalysts for oxidative and reductive synthetic transformations for chemical and pharmaceutical production. Depending on the catalytic behavior of the photogenerated redox centers, there are three major semiconductor photoredox reaction modes: 1) photoexcited hole‐induced oxidations, 2) photoexcited electron‐induced reductions, and 3) photoexcited electron–hole pairs co‐induced redox‐neutral reactions. The characteristics, reaction scopes, and mechanisms of these three semiconductor photocatalysis modes are discussed. Finally, the major challenges and future opportunities regarding the rational design of photoexcited redox centers in advanced synthetic chemistry are provided.
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