Dissecting the Flash Chemistry of Electrogenerated Reactive Intermediates by Microdroplet Fusion Mass Spectrometry

• Published in: Angewandte Chemie International Edition Vol. 60; no. 34; pp. 18494 - 18498
• Main Authors: Hu, Jun, Wang, Ting, Zhang, Wen‐Jun, Hao, Han, Yu, Qiao, Gao, Hang, Zhang, Nan, Chen, Yun, Xia, Xing‐Hua, Chen, Hong‐Yuan, Xu, Jing‐Juan
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 16.08.2021
• Edition: International ed. in English
• Subjects: Cross coupling; Dimerization; electrospray ionization; Intermediates; Mass spectrometry; Mass spectroscopy; Microchannels; microdroplet reaction; Phenothiazine; reactive radical intermediate
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202106945

A novel mass spectrometric method for probing the flash chemistry of electrogenerated reactive intermediates was developed based on rapid collision mixing of electrosprayed microdroplets by using a theta‐glass capillary. The two individual microchannels of the theta‐glass capillary are asymmetrically or symmetrically fabricated with a carbon bipolar electrode to produce intermediates in situ. Microdroplets containing the newly formed intermediates collide with those of the invoked reactants at sub‐10 microsecond level, making it a powerful tool for exploring their ultrafast initial transformations. As a proof‐of‐concept, we present the identification of the key radical cation intermediate in the oxidative dimerization of 8‐methyl‐1,2,3,4‐tetrahydroquinoline and also the first disclosure of previously hidden nitrenium ion involved reaction pathway in the C−H/N−H cross‐coupling between N,N′‐dimethylaniline and phenothiazine. Microreactor on the fly: A special microreactor that permits mass spectrometric probing the flash chemistry of electrogenerated reactive intermediates was demonstrated based on collision mixing of electrosprayed microdroplets, which employed a theta‐glass capillary integrated with carbon bipolar electrodes to produce short‐lived intermediates in situ.