Photocyclization of .alpha.,.alpha.'-diethyl-4,4'-stilbenediol. Isolation of a stable tautomer of the elusive dihydrophenanthrenes

Doyle, Thomas D.; Filipescu, Nicolae; Benson, Walter R.; Banes, Daniel

doi:10.1021/ja00724a064

Cited by 39 publications

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“…After ring closure, the formation of a dihydrophenantrene (DHP) occurs (Fig. To circumvent this problem, Doyle et al performed an experiment by irradiating the synthetic estrogenic hormone diethylstilbestrol (trans-, ' -diethyl-4,4' -stilbenediol) [26,27]. DHP is an unstable compound and will relax back to the stilbene unless trapped by oxidation to form phenantrene, or by elimination given suitable substituent in the ortho-position on one of the aromatic rings in the case of substituted stilbenes [19,20,[22][23][24][25] (Figs.…”

Section: Photochemistry Of Resveratrol Iso-merizationmentioning

confidence: 99%

Chemistry, Stability and Bioavailability of Resveratrol

Francioso¹,

Mastromarino²,

Masci³

et al. 2014

158

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Resveratrol is a bioactive polyphenol found in many vegetables. It is well known for its multiple pharmacological activities, such as anti-inflammatory, antioxidant, antimicrobial, anticancer, neuroprotective and cardioprotective effects. In vitro evidence of resveratrol efficacy is widespread, however, many concerns regarding its effectiveness in vivo arise from its poor stability in vitro and bioavailability following oral ingestion. This review focuses on the in vitro stability, with special focus on the photochemical stability of resveratrol, and on the therapeutic perspectives of this molecule due to its low bioavailability.

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Section: Photochemistry Of Resveratrol Iso-merizationmentioning

confidence: 99%

Chemistry, Stability and Bioavailability of Resveratrol

Francioso¹,

Mastromarino²,

Masci³

et al. 2014

158

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“…As a result, isolated and well-characterized DPHs are extremely rare and seldom observed. 5 , 6 In fact, nearly all of the previously known DHPs could not be isolated or obtained as pure substances due to competing side reactions and/or their poor stability toward ambient conditions.…”

Section: Introductionmentioning

confidence: 99%

Stabilising fleeting intermediates of stilbene photocyclization with amino-borane functionalisation: the rare isolation of persistent dihydrophenanthrenes and their [1,5] H-shift isomers

et al. 2018

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“…35 kcal/mole [ 3 ] . Due to the formation of the keto form however, this difference between VIII and VI is considerably smaller [6]. Thermal cyclisatiolzs of cis-stilbenes have not been observed, though these processes are supposed to precede the cyclo-dehydrogenation to the corresponding phenanthrene derivatives, which occurs only at higher temperatures [3].…”

Section: Xmentioning

confidence: 99%

“…The kinetics of the reaction of I1 with molecular oxygen [2] [5], as well as the mass spectrum of VI which is the keto form of VII, and is formed by photocyclisation of VIII [6], indicate that the 4 a and 4 b hydrogens in the cyclic product are in trans position. Therefore the photocyclisation is a conrotatory process [l].…”

Section: IVmentioning

confidence: 99%

Energy Profiles for Ring Formation‐ and Ring Opening‐Processes in the cis‐Stilbene‐4a,4b‐Dihydrophenanthrene System. An example of the feasibility of a process forbidden by the rules of orbital symmetry conservation

Muszkat

Schmidt

1971

Helvetica Chimica Acta

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Summary. An Extended Hiickel MO treatment of the system cis-stilbene (1)-4a,4b-dihydrophenanthrene (11) indicates that the concerted photocyclisation is a conrotatory process of the first excited electronic state. The activation energies for the photocyclisation and for the thermal ring opening and the ground state energy difference between I and 11, as predicted by the present calculation, are in good agreement with the experimental findings. The observed effects of substituents on the photocyclisation quantum yields are satisfactorily accounted for by a general qualitative treatment and thus indicate that the photocyclisation takes place in the first excited state.We have carried out an MO calculation of the energy profiles for the electrocyclic concerted [l] cyclisation and ring opening processes in the cis-stilbene (I)-4a, 4b-dihydrophenanthrene (11) system3). Scheme A. Initial geometries of cis-stilbene and of 4 a , 4b-dirhydrophenanthrene and numbering system I IIOur calculations indicate that in the lowest excited electronic state, the conrotatory cyclisation of I and the reverse ring cleavage of I1 (photocyclisation and photochemical ring opening) are allowed processes1). As expected [2], this behaviour is entirely parallel to that predicted for the excited state processes in the hexatriene (111)-cyclohexadiene (IV) system by the rules of orbital symmetry conservation laid down by Woodward & Hoffnzann [l]. The similar behaviour in the systems of schemes I n the present context the terms 'allowed' and 'forbidden' refer to the magnitudes of the Boltzmann factors for the respective rate constants.

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Photocyclization of .alpha.,.alpha.'-diethyl-4,4'-stilbenediol. Isolation of a stable tautomer of the elusive dihydrophenanthrenes

Cited by 39 publications

References 0 publications

Chemistry, Stability and Bioavailability of Resveratrol

Chemistry, Stability and Bioavailability of Resveratrol

Stabilising fleeting intermediates of stilbene photocyclization with amino-borane functionalisation: the rare isolation of persistent dihydrophenanthrenes and their [1,5] H-shift isomers

Energy Profiles for Ring Formation‐ and Ring Opening‐Processes in the cis‐Stilbene‐4a,4b‐Dihydrophenanthrene System. An example of the feasibility of a process forbidden by the rules of orbital symmetry conservation

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