TY - JOUR
T1 - Triplet-sensitised photolysis of the photoisomer of a 2,11-diaza[3,3](9,10) anthracenoparacyclophane
T2 - An adiabatic cycloreversion and a [2πa + 2πa + 2σs] rearrangement in a triplet state of the biplanophane system
AU - Okamoto, Hideki
AU - Yamaji, Minoru
AU - Satake, Kyosuke
AU - Tobita, Seiji
AU - Kimura, Masaru
PY - 2004/11/12
Y1 - 2004/11/12
N2 - The triplet-sensitized photoreactions of the title biplanophane system 6, the photoisomer of a 2,11-diaza[3,3](9,10)anthracenoparacyclophane derivative 5, were investigated by stationary and laser-flash photolyses using xanthone (XT) and benzophenone (BP) as triplet sensitizers. When photoisomer 6 underwent XT-sensitized irradiation, a triplet cyclophane 5 and a novel polycyclic product 7 were obtained via an adiabatic cycloreversion and a formal [2πa + 2πa + 2σs] rearrangement, respectively. The maximum quantum yield for the formation of cyclophane 5 (0.69) and the upper-limit efficiency for the formation of polycycle 7 (0.31) were determined by laser photolysis techniques. For BP-sensitized photolysis of photoisomer 6, oxetane 8, in addition to triplet cyclophane 5 and polycycle 7, was formed by a Paterno-Büchi reaction. The quenching rate constant (kq) of triplet BP by photoisomer 6 (3.4 × 108 dm3 mol-1 s-1) was found to be 1 order of magnitude smaller than that for XT (5.0 × 109 dm3 mol-1 s-1). On the basis of the relationship between kq and the triplet donor-acceptor energy gap, the triplet energy level of photoisomer 6 was estimated to be ∼71 kcal mol-1. The photochemical and the photophysical processes involved in the sensitized photolyses are summarized in an energetic reaction diagram and discussed in detail.
AB - The triplet-sensitized photoreactions of the title biplanophane system 6, the photoisomer of a 2,11-diaza[3,3](9,10)anthracenoparacyclophane derivative 5, were investigated by stationary and laser-flash photolyses using xanthone (XT) and benzophenone (BP) as triplet sensitizers. When photoisomer 6 underwent XT-sensitized irradiation, a triplet cyclophane 5 and a novel polycyclic product 7 were obtained via an adiabatic cycloreversion and a formal [2πa + 2πa + 2σs] rearrangement, respectively. The maximum quantum yield for the formation of cyclophane 5 (0.69) and the upper-limit efficiency for the formation of polycycle 7 (0.31) were determined by laser photolysis techniques. For BP-sensitized photolysis of photoisomer 6, oxetane 8, in addition to triplet cyclophane 5 and polycycle 7, was formed by a Paterno-Büchi reaction. The quenching rate constant (kq) of triplet BP by photoisomer 6 (3.4 × 108 dm3 mol-1 s-1) was found to be 1 order of magnitude smaller than that for XT (5.0 × 109 dm3 mol-1 s-1). On the basis of the relationship between kq and the triplet donor-acceptor energy gap, the triplet energy level of photoisomer 6 was estimated to be ∼71 kcal mol-1. The photochemical and the photophysical processes involved in the sensitized photolyses are summarized in an energetic reaction diagram and discussed in detail.
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U2 - 10.1021/jo048757m
DO - 10.1021/jo048757m
M3 - Article
C2 - 15527262
AN - SCOPUS:8644242182
VL - 69
SP - 7860
EP - 7868
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
SN - 0022-3263
IS - 23
ER -