Chen Yiyun, research group of Shanghai Institute of organic chemistry, has made progress in the field of visible light promoted boracic acid addition without additional reagents

Carbonyl compounds are important building blocks in organic synthesis, which can be attacked by nucleophiles to obtain corresponding alcohols However, carbonyl compounds, especially ketones, are particularly difficult to accept free radical addition reaction, because the alkoxy radical intermediates are prone to reverse β - cracking reaction Lactic acid compounds, including the anti parasympathetic drugs oxybutynin and Weichangning, can be synthesized by the nucleophilic addition reaction of metal alkyl reagents to ketoacids However, these nucleophilic addition methods are sensitive to air and water, and the strong alkalinity of alkyl metal reagents is easy to cause various side reactions Therefore, it is necessary to develop new efficient and mild synthesis methods of lactate derivatives, especially by exploring new mechanism models Chen Yiyun, a research group of the State Key Laboratory of life organic chemistry, Shanghai Institute of organic chemistry, Chinese Academy of Sciences, is committed to the development of biocompatible visible light chemistry Recently, it was reported that the visible light promoted addition reaction of borate ketoacids without additional reagents to achieve efficient synthesis of lactate compounds The results were published in J am Chem SOC (DOI: 10.1021 / JACS 9b09099) Organoboron compounds are cheap and easy to obtain, which are commonly used as alkyl radical precursors α - ketoacids are usually used as acyl donors in free radical reactions, and in this work, they can be used as free radical acceptors for the first time to construct quaternary carbon atom centers By means of NMR and absorption spectroscopy, it is found that α - keto acid and alkyl boric acid can form a new molecular complex, and promote the visible light absorption of the keto acid boric acid complex The molecular complex promotes the formation of alkyl radicals under visible light, the addition of alkyl radicals to ketoacids, and avoids the reverse fracture of newly formed carbon carbon bonds In this method, no additional reagents are needed, and only visible light can be used to initiate the addition reaction of borate ketoacids to achieve the efficient synthesis of various lactic acid derivatives A series of mechanism experiments show that the reaction is a free radical chain reaction, and the flow photoreactor can be used to prepare important lactic acid drug precursors without additional reagents The new strategy of boron reagent activating ketoacids can be extended to the addition reaction of dihydropyridine derivatives as free radical precursors to ketoacids By adding boron reagent as Lewis acid, the addition reaction of primary, secondary and even tertiary alkyl free radical precursors to ketoacids can be realized The reaction can be carried out in the mixed solution of organic solvent and water, which has the potential of biological coupling reaction The first author of this paper is Xie Shasha, a doctoral student The above research was supported by NSFC, Chinese Academy of Sciences strategic leading science and technology project (class B), National Key Laboratory of life organic chemistry and Chinese Academy of Sciences.