Synthesis of S-Pixyl Derivatives for Mass Spectrometric Applications

Synthesis of novel S-pixyls based on the thioxanthyl skeleton is described. Thioxanthone derivatives were prepared by a regioselective intramolecular Friedel-Crafts acylation reaction and converted into S-pixyl derivatives by Grignard synthesis. S-Pixyl carbocations stabilised by electron donating groups on the thioxanthyl backbone produced exceptional mass spectra under (MA)LDI conditions (laser desorption ionisation, both with and without ­matrix), and can be detected down to femtomol levels.