Mass spectrometric studies of benzoxazine resorcarenes

Eleven differently substituted 3,4-dihydro-2H-1,3-benzoxazine resorcarenes were studied by electrospray ionisation (ESI) and matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry, using Fourier transform ion cyclotron resonance (FT-ICR) and time-of-flight (TOF) mass spectrometers, respectively. Under ESI conditions it was possible to transfer the intact resorcarenes from solution to the gas phase, yielding [M + H](+) and [M + 2H](+) ions as the main ions observed. Energy increase of the ions induced ready decomposition through successive eliminations of four CH(2)NR groups. Ion-molecule reactions showed that the ionising proton was situated somewhere inside the molecule and could not be reached with neutral reagent gases. In the host-guest complexation experiments, the benzoxazine resorcarenes studied turned out to be poor hosts for alkali metal and ammonium ions. In MALDI experiments, 2,5-dihydroxybenzoic acid proved to be the best matrix for these compounds. However, the intensity of the [M + H](+) ions was low for all compounds, and extensive fragmentation with consecutive elimination of CH(2)NR groups was observed.