Search

Regioselective benzanilide bromination that generates either regioisomer from the same starting material is desirable. Herein, we develop switchable site-selective C(sp2)-H bromination by promoter regulation. This protocol leads to regiodivergent brominated benzanilide starting from the single substrate via selection of promoters. The protocol demonstrates excellent regioselectivity and good tolerance of functional groups with high yields. The utility effectiveness of this method has been well exemplified in the late-stage modification of biologically important molecules. [ABSTRACT FROM AUTHOR]

Rationale Methods Results Conclusions Electronically mismatched Diels–Alder reactions have gained much attention as an alternative pathway for C–C bond formation. To facilitate the development of facile organic transformations, mechanistic investigations are required. Spectroscopic methods (NMR, electron paramagnetic resonance and UV–visible) are normally adopted for mechanistic examinations, but further improvements in directly obtaining structural information of short‐lived intermediates are encouraged. Herein, an electronically mismatched Diels–Alder reaction between indole and 1,3‐cyclohexadiene was studied using in situ electrospray ionization mass spectrometry (in situ ESI‐MS). Based on direct sampling and detection of the in situ ESI‐MS without sample pretreatment, the structures and dynamics of important intermediates were examined on‐line.A syringe‐based photocatalytic reactor and in situ ambient MS (AMS) evaluation system was constructed for mechanism studies. The role of oxygen was confirmed via control reaction employed in the N2‐bubbled system. The stepwise cation radical‐based pathway and the [2 + 2] cycloaddition process were determined through a series of experiments, including solvent evaluation, MS/MS experiments and dynamic monitoring.The dependence of the reaction on solvent polarity demonstrated that the reaction occurs via the formation of cation radicals, which were captured, identified and dynamically monitored via in situ ESI‐MS. Without pre‐separation, the intermediate of [2 + 2] cycloaddition was identified and the cycloaddition process was thereby determined to be the combination of [4 + 2] cycloaddition and [2 + 2] cycloaddition. In addition, oxygen was proved to act as an electron mediator for both catalyst Ru(bpz)3(PF6)2 and radical cations.The mechanism of an electronically mismatched Diels–Alder reaction was successfully deduced by in situ MS associated with a syringe‐based photocatalytic reactor. The structures and dynamics of cation radicals, the effect of O2 for the reaction and the detailed process of [2 + 2] cycloaddition have been well demonstrated. This work could not only promote the understanding and development of facile photocatalytic transformations, but also enlarge the application range of AMS in on‐line monitoring. [ABSTRACT FROM AUTHOR]

Chemical reactions conducted in different media (liquid phase, gas phase, or surface) drive developments of versatile techniques for the detection of intermediates and prediction of reasonable reaction pathways. Without sample pretreatment, ambient mass spectrometry (AMS) has been applied to obtain structural information of reactive molecules that differ in polarity and molecular weight. Commercial ion sources (e.g., electrospray ionization, atmospheric pressure chemical ionization, and direct analysis in real‐time) have been reported to monitor substrates and products by offline reaction examination. While the interception or characterization of reactive intermediates with short lifetime are still limited by the offline modes. Notably, online ionization technologies, with high tolerance to salt, buffer, and pH, can achieve direct sampling and ionization of on‐going reactions conducted in different media (e.g., liquid phase, gas phase, or surface). Therefore, short‐lived intermediates could be captured at unprecedented timescales, and the reaction dynamics could be studied for mechanism examinations without sample pretreatments. In this review, via various AMS methods, chemical reaction monitoring and mechanism elucidation for different classifications of reactions have been reviewed. The developments and advances of common ionization methods for offline reaction monitoring will also be highlighted. [ABSTRACT FROM AUTHOR]

By simple microwave irradiation, a high-throughput, single-step, rapid but controllable synthesis of stable colloidal CsPbX3 perovskite NCs with tunable properties and morphologies (nanocubes, nanorods, nanowires, quadrate nanoplates and hexagonal nanoplates) was achieved. It was employed in a heterogeneous solid–liquid reaction system within minutes without any tedious pre-preparation. [ABSTRACT FROM AUTHOR]