Electron-Transfer-Catalyzed Dimerization of trans-Anethole: Detection of the Distonic Tetramethylene Radical Cation Intermediate by Extractive Electrospray Ionization Mass Spectrometry

The desolvating droplets of EESI were used as microreactor for the mass spectrometric study of short-lived transients of reactions in condensed liquid phase in the millisecond time region, The electron-transfer-catalyzed dimerization of trans-anethole was investigated and the intermediates in the radical cation chain reaction were isolated and characterized by MS-MS. The distonic tetramethylene radical cation 3(o)(.+) was detected as intermediate, and its cyclization to give the cyclobutane radical cation 3(c)(.+) was observed giving strong evidence that the reaction takes place stepwise.