A mechanistic study, principally based on product analysis, relative to the TiO2-photosensitized oxidation of indane and some of its hetero-analogues, in deaerated CH3CN and in the presence of Ag2SO4, was performed. In particular: (i) 1-acetamidoindan (principal product), indene, 1-indanol and 1-indanone were obtained from indan; (ii) 5-methoxyindan gave 6-methoxyindene (principal product) and 5-methoxy-1-indanone; (iii) 2,3- dihydrobenzofuran, 2,3-dihydroindole and 2,3-dihydrobenzothiophene produced benzofuran, indole and benzothiophen (the last one accompanied by minor amounts of 2,3-dihydrobenzothiophene-1-oxide), respectively. Considering the previous studies on photo-oxidation of analogous substrates as benzylic derivatives (arenes, alcohols and ethers) and from reaction product profiles, an electron-transfer mechanism (from the substrate to the photogenerated hole) is suggested, where the radical cation intermediate should deprotonate to a benzylic radical. The carbocation obtained from the oxidation of this radical should competitively evolve to alkene, alcohol and acetamide. H2 18O labelling photo-oxidation experiments suggest that the ketone, when present, should derive from the substrate, through the alcohol as intermediate.
TiO2-sensitised photo-oxidation mechanism of indane and some of its hetero-analogs in deaerated CH3CN
BETTONI, Marta;DEL GIACCO, Tiziana;ROL, Cesare;SEBASTIANI, Giovanni Vittorio
2006
Abstract
A mechanistic study, principally based on product analysis, relative to the TiO2-photosensitized oxidation of indane and some of its hetero-analogues, in deaerated CH3CN and in the presence of Ag2SO4, was performed. In particular: (i) 1-acetamidoindan (principal product), indene, 1-indanol and 1-indanone were obtained from indan; (ii) 5-methoxyindan gave 6-methoxyindene (principal product) and 5-methoxy-1-indanone; (iii) 2,3- dihydrobenzofuran, 2,3-dihydroindole and 2,3-dihydrobenzothiophene produced benzofuran, indole and benzothiophen (the last one accompanied by minor amounts of 2,3-dihydrobenzothiophene-1-oxide), respectively. Considering the previous studies on photo-oxidation of analogous substrates as benzylic derivatives (arenes, alcohols and ethers) and from reaction product profiles, an electron-transfer mechanism (from the substrate to the photogenerated hole) is suggested, where the radical cation intermediate should deprotonate to a benzylic radical. The carbocation obtained from the oxidation of this radical should competitively evolve to alkene, alcohol and acetamide. H2 18O labelling photo-oxidation experiments suggest that the ketone, when present, should derive from the substrate, through the alcohol as intermediate.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
