Photochemical synthesis: Using light to build C–C bonds under mild conditions

Abstract

A review of recent advancements in metal-free arylations via photogenerated triplet aryl cations and decatungstate anion ([W 10 O 32 ] 4À ) photocatalyzed CeC bond formation is reported herein. These approaches are two examples of the great potentialities of photons as green activants in organic synthesis, allowing the functionalization of different chemical substrates under mild conditions (room temperature, aqueous solvents, absence of aggressive and unstable reactants and of expensive transition metal-based catalysts, and chance to use solar light as the energy source).

Metal-free synthesis of biarenes via photoextrusion in di(tri)aryl phosphates

“…While aryl phosphates have been only sparsely used as substrates in thermal cross-coupling reactions [65][66][67], their photochemical behavior has been the subject of various investigations in the last decades [28,29,64,68]. Simple (electron-rich) monoaryl phosphates are known to undergo the photoheterolysis of the Ar-O bond to form aryl cations [28,36].…”

“…As for the last issue, there is nowadays a growing interest in the forging of Ar-Ar bonds under transition-metal-free conditions [24,25]. Apart the most common pathways, e.g., the Friedel-Crafts functionalization [26] or nucleophilic aromatic substitution [27], alternative approaches have emerged that make use of photogenerated intermediates (triplet aryl cations [28,29] or aryl radicals [30,31]). As for the former case, the intermolecular formation of a biaryl arose from the photoheterolysis of an Ar-N bond (in arene diazonium salts or their derivatives [32,33]), of an Ar-Cl bond [34,35], of an Ar-O bond (in aryl phosphates [36], aryl sulfonates [36], and in aryl trifluoroethyl sulfate [37], Scheme 1: Synthesis of biarenes via a) photogenerated triplet aryl cations and aryl radicals (PC = photocatalyst), b) intramolecular free radical ipso substitution, c) thermally catalyzed extrusion of CO and SO 2 , d) photoinduced photoextrusion from benzene sulfonamides I and phosphonates II, and e) photoextrusion from diaryl-(III) and triaryl (IV) phosphates.…”

Research on the Impact of Green Credit on the Financial Performance of Commercial Banks

“…Green credit means that commercial banks actively guide the flow of funds through credit means, reduce loans to industries and projects with "high pollution, and overcapacity", while increasing credit support for low-emission and low-polluting industries and projects, and gradually changing the "extensive" business "Business model to promote the development of local green economy. From the data of 21 major banks in my country at the end of June 2019, it can be seen that although the total amount of green credit has reached more than 10 trillion yuan, it is showing a situation of high growth rate and low proportion", with an annual growth rate of 12.8%, And the proportion is only maintained at about 6.5% [2] . Green credit has a certain impact on the competitiveness of commercial banks and environmental risk management.…”

“…In recent years, scholars have conducted a lot of theoretical and empirical analysis on the issue of green credit affecting the financial performance of commercial banks. Wang Xiaoluo proposed that environmental governance investment will increase with improvement of bank assets quality [1] ; Lazzatoni et al believe that the development of green finance will have a significant impact on the financial performance of commercial banks [2] ; Campiglio proposed that commercial banks should avoid the status quo of its own operations may have adverse effects, and may refuse to lend to low-carbon businesses and environmentally friendly companies [3] ; Zhang Changjiang and others discussed the relationship between green credit and commercial bank performance based on the intermediary effect of green reputation, and believed that despite the implementation of green credit policies, Commercial banks will still cause adverse effects, but green credit lending behavior will produce green reputation effects, which can play a positive role in improving the financial performance of commercial banks [4] ; Yan Tingfeng et al proceeded from the perspective of systems, technology, and institutions, It is believed that the short-term effect of green credit on the financial performance of commercial banks is weak, but the long-term effect is more obvious, because the status quo of low income and high cost of green credit in the short term is difficult to improve quickly, which affects their operating profits, but helps to improve their profitability in the long run [5] .…”

Photoinduced Processes as a Way to Sustainable Polymers and Innovation in Polymeric Materials

“…The reactions that Ciamician studied with his associate Paul Silber are hydrogen abstraction by carbonyls promoting reduction, reductive dimerization and reductive alkylation, and by nitro-compounds, α-cleavage of ketones, [2 + 2] cycloaddition of olefins, oxygenation and double-bond isomerization. From those times, many other photochemical methods have been developed further demonstrating that they are highly effective for the synthesis of organic compounds [ 8 ]. In fact, UV and visible photons have an energy content comparable to that of chemical bonds: upon absorption, electronically excited states are formed and start different chemical paths leading to chemical transformations of synthetic interest.…”