Premium
Photocatalyzed Oxidation of Cyclohexene and Cyclooctene with ( n Bu 4 N) 4 W 10 O 32 and ( n Bu 4 N) 4 W 10 O 32 /Fe III [ meso ‐Tetrakis(2,6‐dichlorophenyl)porphyrin] in Homogeneous and Heterogeneous Systems
Author(s) -
Molinari Alessandra,
Amadelli Rossano,
Carassiti Vittorio,
Maldotti Andrea
Publication year - 2000
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(200001)2000:1<91::aid-ejic91>3.0.co;2-j
Subject(s) - cyclooctene , chemistry , cyclohexene , allylic rearrangement , photochemistry , porphyrin , chemoselectivity , radical , singlet oxygen , oxidizing agent , photocatalysis , cyclohexane , epoxide , chloride , decomposition , catalysis , organic chemistry , oxygen
Photoexcitation of ( n Bu 4 N) 4 W 10 O 32 is a suitable mean of oxidizing cyclohexene and cyclooctene with O 2 at room temperature and pressure. This process can be carried out in homogeneous solution as well as using the decatungstate in a dispersed form after its heterogenisation on silica. Cyclohexene and cyclooctene are mainly oxidized to the corresponding hydroperoxides as a consequence of primary photoprocesses which lead to the formation of allylic radicals. The presence of the Fe III [ meso ‐tetrakis(2,6‐dichlorophenyl)porphyrin] chloride as cocatalyst strongly affects the photocatalytic properties of ( n Bu 4 N) 4 W 10 O 32 , playing a key role in the allylic‐hydroperoxide dependent oxidation of the cycloalkenes. In the photooxidation of cyclohexene, the porphyrin increases the photocatalytic efficiency of the decatungstate in terms of total turnover number and catalyses the decomposition of cyclohexenyl hydroperoxide with the selective formation of cyclohex‐2‐en‐1‐ol. On the other hand, its presence during the photoinduced oxidation of cyclooctene favours the formation of cyclooctene epoxide by addition of ROO · and RO · radicals to the double bond. In the case of cyclooctene, the heterogenisation of the decatungstate on the solid support also affects the chemoselectivity of the photocatalytic process in the absence of the iron porphyrin complex.