Visible-light mediated photoredox reactions have recently emerged as a powerful means for organic synthesis and thus have generated significant interest from the organic chemistry community. Although the reaction mechanisms have been probed by a number of techniques such as NMR, fluorescence quenching, and laser flash photolysis and various degree of success has been achieved, mechanistic ambiguity still exists (for instance, the involvement of the chain mechanism is still under debate) due to lack of structural information about the proposed and short-lived intermediates. Herein, we present the detection of transient amine radical cations involved in intermolecular [3+2] annulation reaction of N-cyclopropylaniline (CPA, 1) and styrene 2 by electrospray ionization mass spectrometry (ESI-MS) in combination with online laser irradiation of the reaction mixture. In particular, the reactive CPA radical cation 1+·, the reduced photocatalyst Ru(I)(bpz)3 +, and the [3+2] annulation product radical cation 3+· are all successfully detected and confirmed by high resolution MS. More importantly, the post-irradiation reaction with an additional substrate, the isotope-labeled CPA following photolysis of 1, 2 and Ru catalyst provide strong evidences to support the chain mechanism in the [3+2] annulation reaction. Furthermore, the key step of the proposed chain reaction, the oxidation of CPA 1 to amine radical cation 1+· by product radical cation 3+· (generated using online electrochemical oxidation of 3) is successfully established. Additionally, the coupling of ESI-MS with online laser irradiation has been successfully applied to probe the photostability of photocatalysts.

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We report the use of an online electrochemistry/mass spectrometry platform to develop a redox neutral electrosynthesis of 5-membered rings via [3 + 2] annulation of N-cyclopropylanilines and alkenes, without additional oxidant, reductant or catalyst.

Dysregulation of microRNAs (miRNAs) and their targeted downstream genes is involved in the carcinogenesis and progression of colorectal cancer (CRC). miR-519b-3p has been reported to play an important role in several cancers. However, its function in CRC is unclear. In this study, we detected the expression of miR-519b-3p in CRC tissues and cell lines, and determined the potential role of miR-519b-3p in cell proliferation and invasion in CRC. Also, the downstream gene of miR-519b-3p was determined. Our results showed that miR-519b-3p was notably reduced in CRC specimens and cell lines. Overexpression of miR-519b-3p inhibited the proliferation and invasion of RKO and DLD-1 cells, whereas knockdown of miR-519b-3p had the contrary effect. The ubiquitous mitochondrial creatine kinase (uMtCK) was identified as a direct target of miR-519b-3p in CRC using luciferase assay. Additionally, miR-519b-3p expression was negatively correlated with uMtCK expression in CRC specimens. Notably, the miR-519b-3p suppressed the uMtCK/Wnt signaling pathway in CRC cells, thereby suppressing CRC cell proliferation and invasion. The inhibition of uMtCK by miR-519b-3p may provide a promising option for the treatment of CRC.