Photo‐Diels‐Alder‐Reaktionen mit Anthracen

Abstract

are studied and discussed in terms of the experimentally detected two-step mechanism via intermediates. It is shown, that photochemistry extends the scope of Diels-Alder reactions. In one case (with dimethyl muconate) exciplex formation could be detected, which does not facilitate but on the contrary hinders photoaddition. The structures of all new adducts follow from spectroscopic data, independent syntheses, or comparison with new reference compounds. Some chemical transformations are studied in order to clarify some discrepancies with literature reports.Photo-Diels-Alder-Additionen mit Cyclopentadien und 1,3-Cyclohexadien konnen mit verschiedenen Ketonen sensibilisiert werden. Dies wurde friihzeitig zur Synthese von ,,exoAddukten" herangezogenl. 2.3), welche thermisch nicht ohne weiteres zuganglich waren. Auch durch direkte Lichtabsorption angeregte Dienophile wie Acenaphthylen" oder Diphe-1) N . J.

Diels–Alder reactions of anthracene, 9-substituted anthracenes and 9,10-disubstituted anthracenes

“…The use of (9-anthryl)methyl methyl fumarate in a tethered photochemical cycloaddition gave a 66% yield of the desired addition product, 150 an improvement on the untethered reaction that required a high concentration of dimethyl fumarate. 25,26 The cis isomer was not detected and no dimer was formed.…”

“…An extensive study into the photochemical Diels -Alder reactions of anthracene 2 revealed that high-frequency UV light results in photoinduced electron transfer to produce anthracene in a singlet state form 2 p . 25,26 This quickly reacted via a diradical mechanism with a variety of electrondeficient dienophiles to give the adducts 8 and 9 (Scheme 2). The formation of the intermediate 7 allows rotation around the C -C bond, leading to the selective formation of the more stable trans-adduct 8.…”

Triplet–Triplet Annihilation Upconversion in a MOF with Acceptor‐Filled Channels

“…Hence, oleic acid [(9 Z )‐octadec‐9‐enoic acid] was mixed with DPA and the fluorescence recorded. However, under laser irradiation, DPA and oleic acid seemed to react, possibly by a cycloaddition reaction . Hence, we employed the photostable saturated surfactant caprylic acid (CA, C 8 H 16 O 2 ).…”

“…However,u nder laser irradiation, DPAa nd oleic acid seemed to react, possibly by a cycloaddition reaction. [40] Hence, we employed the photostable saturated surfactant caprylic acid (CA, C 8 H 16 O 2 ). In the as-synthesized PCN-222(Pd), the Zr 6 cluster contains two terminal OH ligands, one of which points into the hexagonal channel, providing six OH groups per channel segmentf or the functionalization with carboxylic acids (Figure 1b).…”

Photophysics and photochemistry of coupled chromophores: lepidopterene and its dimethyl derivative

“…Exciplexes are often proposed as intermediates in the photoaddition of olefins to anthracenes.7 However, there are remarkably few cases where significant exciplex emission has been observed, and these all involve cyano-or chloro-substituted anthracenes.8-10 In some cases, the intermediacy of the exciplexes has been refuted in favour of a biradical intermediate. * 11 Lepidopterenes provide the first unambiguous demonstration of an (unsubstituted) anthracene-ethylene exciplex,5,6 and further study of their kinetic and thermodynamic properties is desirable. Currently, there is also considerable interest in the mechanism of adiabatic photochemical reactions.12,13 Lepidopterenes show remarkably efficient adiabatic photodissociation, approaching 90% at room temperature, and the present work is part of our continuing investigation of the adiabatic photoreactions of coupled chromophores.14,15…”