Halogenated oxo- and peroxotitanium porphyrinates as sensitizers for the photooxygenation of olefinic compounds
摘要:
A series of porphines, oxotitanium(IV) and peroxotitanium(IV) porphyrinates were tested as photosensitizers of the singlet oxygen ene reaction with cyclohexene and cis-cyclooctene. The relative order of activity is: H-2(P) > O=Ti(P) greater than or equal to Ti(O-2)P. Best stability is obtained for porphines or porphyrinate complexes with fluorine substituents. Oxotitanium(IV) porphyrinates are active in the decomposition of allylic hydroperoxides. The (photo)catalytic epoxidation occurs less readily than the thermal reaction at 82 degrees C. Attempts of photocatalytic hydrogen peroxide activations lead to fast destruction of O=Ti(P). (C) 1999 Elsevier Science B.V. All rights reserved.