Photochemische Reaktionen. 2. Mitteilung. Über gegenseitige Beziehungen und Umwandlungen bei Bestrahlungsprodukten des Santonins

Arigoni, D.; Bosshard, Hans Heinrich; Bruderer, H.; Büchi, G.; Jeger, O.; Krebaum, L. J.

doi:10.1002/hlca.19570400621

Cited by 79 publications

(18 citation statements)

References 9 publications

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“…Under different reaction conditions the two distinct reaction pathways are competitive. It has been reported [19] that in dioxane the reaction would follow path B rather than path A. In contrast, the reaction proceeds along path A in the crystal.…”

Section: The Competitive Reaction Pathway In the Cleavage Of The Càc mentioning

confidence: 88%

“…[16,17] Many experiments were carried out to explore the photoproducts derived from the a-santonin photochemical reaction in different solvents and a remarkable progress in the structural assignments was made. [18,19] However, the intermediates and products involved in the santonincrystal reaction pathway are less characterized. In 1968, Matsuura and co-worker assumed that during the reaction an unstable intermediate is formed which subsequently yields a product through Diels-Alder and [2+2] cycloaddition reactions.…”

Section: Introductionmentioning

confidence: 99%

“…[19,21,23] From the experimental point of view, it has been proposed that the reaction in the solid state is initiated by the C4ÀC5 bond cleavage in INT, generating the intermediate A-INT. A 1,2-H shift takes then place in this zwitterionic species, involving the two carbon atoms C2 and C4 of A-INT.…”

Section: Introductionmentioning

confidence: 99%

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Theoretical Studies on the Photoinduced Rearrangement Mechanism of α‐Santonin

et al. 2011

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α-Santonin is the first organic compound observed to feature a photoinduced rearrangement and is now known to undergo a series of photochemical processes under UV irradiation. On the basis of the considerable interest of this system as a prototype, and of the yet limited insights reached for the basic photo mechanisms, we calculate the high-level electronic structures and explore the potential energy surfaces (PES) of α-santonin in the ground and lowest-lying excited states, their couplings, and the possible photoinduced isomerization pathways. The calculations identify the low-lying singlet excited state (1)(nπ*) accessible under light irradiation, which decays to the low-energy (3)(ππ*) state through an intersystem crossing in the Franck-Condon region to initiate the photoinduced rearrangement. The initial reaction from the C3-C5 bond coupling, which takes place on the (3)(ππ*) state potential energy surface, leads to a three-membered alkyl-ring compound intermediate state INT. The following photochemical reactions have the possibility to arise from two distinct C-C bond cleavages, C4-C5 and C3-C4, denoted as path A and path B. Path A is favored both dynamically on the excited-state PES and thermodynamically on the ground-state PES in vacuo. Experiments show that it also becomes the dominant photoinduced rearrangement process in the crystal, which can be explained by considering the requirement for less space and the stacking effect under the confined environment. Path B is dynamical advantaged both on the ground- and excited-state PESs in a weak polar solvent, such as dioxane. Once the biradical intermediate B-INT is accessible on the ground-state PES, the formation of the product B-P is almost barrier free.

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Section: The Competitive Reaction Pathway In the Cleavage Of The Càc mentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

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Theoretical Studies on the Photoinduced Rearrangement Mechanism of α‐Santonin

et al. 2011

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“…(55) isolated isophotosantonic lactone fl05) from the irradiation of santonin (104) in aqueous acetic acid. In the same year Jeger (Arigoni et al,56) reported the isolation of lumi-santonin (106). In 1958 Barton e^ al.…”

Section: £=R\j 68 53mentioning

confidence: 99%

Photochemistry of keto-pregnane derivatives

Sandner

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gave 37 per cent of 48 (R = (CH^ÏgCH-) and 22 per cent of 49. Irradiation in tertiary butyl alcohol, dioxane or benzene gave 43, 31 and 72 per cent of ^ respectively. No ^ was detected in these solvents. It would appear that the addition of solvent can compete with rearrangement in this case for solvents of low steric bulk, but that rearrangement is favored with a bulky solvent such as tertiary butyl alcohol and with those for which hydrogen abstraction is not a facile process such as dioxane and benzene.

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“…Photochemical rearrangements of cyclohexadlenones Santonin (XXX) was the first cross-conjugated dlenone to be irradiated (28) Plsch and Richards (34) reported that the santonin -+ lumisantonin rearrangement (XXX -* XXXI ) was sensitized by benzophenone and suggested that it was probably the result of excitation to the rr, TT* triplet sLate. This implied that the rearrangement was due to an electron deficient carbon skeleton.…”

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confidence: 99%

The photochemistry of some 2-cyclohexenones

Rettig

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Photochemische Reaktionen. 2. Mitteilung. Über gegenseitige Beziehungen und Umwandlungen bei Bestrahlungsprodukten des Santonins

Abstract: Irradiation of santonin in dioxan solution or in alcohol yields a new isomer, lumisantonin, which in turn has been correlated with 3 known compounds: photosantonin, photosantonic acid and isophotosantonic acid lactone. The chemistry of lumisantonin is interpreted in terms of structure b.

Cited by 79 publications

References 9 publications

Theoretical Studies on the Photoinduced Rearrangement Mechanism of α‐Santonin

Theoretical Studies on the Photoinduced Rearrangement Mechanism of α‐Santonin

Photochemistry of keto-pregnane derivatives

The photochemistry of some 2-cyclohexenones

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