A Tandem Dehydrogenation‐Driven Cross‐Coupling between Cyclohexanones and Primary Amines for Construction of Benzoxazoles
作者:Biping Xu、Weiping Su
DOI:10.1002/anie.202203365
日期:2022.7.25
A tandem dehydrogenation-driven cross-coupling reactionbetweencyclohexanones and primary amines is reported for benzoxazole synthesis by TEMPO's multiple reactivity modes (oxygenation and desaturation). This transition metal-free protocol features broad substrate scope, high functional group tolerance, and is operationally simple, therefore enabling late-stage functionalization and rapid synthesis
据报道,通过 TEMPO 的多种反应模式(氧化和去饱和)合成苯并恶唑,环己酮和伯胺之间的串联脱氢驱动的交叉偶联反应。这种无过渡金属方案具有广泛的底物范围、高官能团耐受性和操作简单,因此能够实现生物活性化合物的后期功能化和快速合成,包括结构复杂的上市药物和天然产物。
Design and development of a fluorescent probe for monitoring hydrogen peroxide using photoinduced electron transfer
A novel fluorescent probe, 7-hydroxy-2-oxo-N-(2-(diphenylphosphino)ethyl)-2H-chromene-3-carboxamide (DPPEA-HC) was developed for use in monitoring hydrogen peroxide (H2O2) production. DPPEA-HC, which consists of a diphenylphosphine moiety and a 7-hydroxycoumarin moiety, reacts with H2O2 to form DPPEA-HC oxide, which is analogous to the reaction of triphenylphosphine with hydroperoxides such as H2O2 to form triphenylphosphine oxide. Photoinduced electron transfer (PET) was applied in the design of DPPEA-HC. Since the diphenylphosphine moiety and the 7-hydroxycoumarin moiety would act as the PET donor and the acceptor, respectively, it would be expected that DPPEA-HC would rationally cancel the PET process via the formation of DPPEA-HC oxide, based on the calculated energy levels of the donor and the acceptor moieties using the B3LYP/6-31G*//AM1 method. The fluorescence intensity of DPPEA-HC increased on the addition of a H2O2 solution in 100 mM sodium phosphate buffer (pH7.4), as predicted from the energy level calculation and a good correlation between increase in the fluorescence of DPPEA-HC and the concentration of H2O2 was observed. DPPEA-HC was also fluoresced by H2O2, which was enzymatically produced in xanthine/xanthine oxidase/superoxide dismutase (XA/XOD/SOD) system. The increase in the fluorescence of DPPEA-HC in the presence of H2O2 immediately ceased on the addition of catalase (CAT), which catalyzes the disproportionation of H2O2. In addition, DPPEA-HC was found to have a much higher selectivity for H2O2 and a greater resistance to autoxidation than 2',7'-dichlorodihydrofluoresein (DCFH). Time-resolved fluorescence measurements of DPPEA-HC and DPPEA-HC oxide confirmed that the fluorescence off/on switching mechanism of DPPEA-HC is based on the PET on/off control. (C) 2004 Elsevier Ltd. All rights reserved.