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.