Synthesis and E-Beam-Mediated Gas Phase Fragmentation of Thiol-Containing Furoxans for Nanopatterned Alkyne Formation on Gold Surface

Furoxanthiols PFT and BPFT possessing thiomethyl or thiobenzyl groups in the furoxan ring were designed and synthesized as potential light-sensitive alkyne precursors on a gold surface. The synthesis of thiofuroxans PFT and BPFT was performed from the corresponding halofuroxans 1b and 2c, respectively, by the substitution with potassium thioacetate in ethyl acetate/ethanol or DMF, followed by basic hydrolysis as the key reactions. Electron-beam-mediated fragmentation of furoxans 1c and 2d in a mass spectrometer afforded the corresponding aryl alkyne fragments, with the evolution of NO in high preference. In the cases of thiofuroxans PFT and BPFT, carbon-sulfur bond cleavage was observed as a representative fragmentation, producing M-SH and M-SAc peaks, which competed with the release of NO. In the fragmentation of mono-aryl furoxan 1c, the release of molecule of NO was predominately observed to produce an M-NO fragment as a base peak by the formation of trimembered thiiranium or azirine intermediate.