Fullerene-Promoted Singlet-Oxygen Photochemical Oxygenations in Glass-Polymer Microstructured Reactors

In this paper we report the fabrication of thiolene-based microstructured reactors (MRs) that have been specifically designed to include solid-supported reagents within the microchannels network. We propose a convenient solution to realize reversible press-fit, leak-proof interconnects that greatly simplify the MR coupling to the external environment such as capillary tubing, sample reservoirs and pumps. The MRs have been used to carry out the oxidation of alpha-terpinene and methionine using [60]fullerene, covalently linked to Tentage](R) and silica gel matrices, as a singlet oxygen sensitizer. High conversions have been observed for both substrates although, in the case of a-terpinene, a partial photodegradation of the endo-peroxide product was detected. Interestingly, in the case of methionine, a quantitative conversion to the corresponding sulfoxides was achieved in about 40 seconds, using lowpower, white LED illumination. The reaction time is considerably shorter when compared to the batch procedure that requires, for the same process, about one hour illumination and the use of a 300-W tungsten halogen lamp.