Photoaddition of ethylenes and acetylenes to hexafluorobenzene

Abstract

Both cis-and rrans-cyclo-octene undergo stereospecific photoreactions with hexafluorobenzene to give various 1 : 1 -cycloadducts which arise via 1.2-and 1.3-addition processes and subsequent isomerisations of the initial adducts.Effects of irradiation wavelength, temperature, and concentration are discussed in connection with the involvement of free and co m p I exed S, h exaf I uoro be nze ne.In contrast, 2.3-dimethylbut-2-ene and hexafluorobenzene gave mainly an acyclic 1 : 1 adduct formed by substitutive addition, and its dehydrofluorination product. Although maleic anhydride and maleimide readily undergo photoaddition to benzene, neither gave photoadducts with hexafluorobenzene.Propyne and but-2-yne give cyclo-octatetraenes by photoaddition to hexafluorobenzene, and in the case of but-2-yne the precursor 1.2-cycloadduct w a s isolated as the sole primary product.In general, the photoadditions to hexafluorobenzene show some points of resemblance to the corresponding

Undoped and Eu3+ Doped Magnesium-Aluminium Layered Double Hydroxides: Peculiarities of Intercalation of Organic Anions and Investigation of Luminescence Properties

“…The potency to absorb the UV radiation by interlayer organic anions and possible transfer this energy to the Eu 3+ center by the interaction between the carboxyl oxygen of the intercalated anions with the hydrogen of the M(OH) 6 octahedra via a hydrogen bond was suggested. The tartrate and benzoate having the strong basicity, showed higher ability to absorb the light [ 30 ]. Carbonate is a weaker base, thus transferring less energy to Eu 3+ ions.…”

Arene–Alkene Cycloaddition

“…Cyclic carbonates also react in an ortho fashion with benzene, but the product rapidly isomerizes to the para adduct under the reaction conditions (with acetophenone sensitization). 35 A similar reaction between hexafluorobenzene and cyclooctenes gave interesting mechanistic insight, 36 showing that the product distribution is time-dependent, eventually reaching a photostationary state. In particular, 6 (as a mixture of isomers amounting to 24%) is absent before the equilibrium (Scheme 8).…”

“…A similar reaction between hexafluorobenzene and cyclooctenes gave interesting mechanistic insight, showing that the product distribution is time-dependent, eventually reaching a photostationary state. In particular, 6 (as a mixture of isomers amounting to 24%) is absent before the equilibrium (Scheme ).…”

The meta photocycloaddition of arenes to alkenes

“…The case of the phenols (entries 21-23), from which the primary adducts cannot be isolated, has been treated in the section on zwitterions. Methoxy has a stronger directing effect than alkyl and the OCH3 group invariably ends up at position bl in adducts derived from alkylsubstituted anisoles (entries [24][25][26][27][28][29][30][31][32][33][34]. The cyano group competes with methoxy and from p-cyanoanisole (entry 38) a considerable amount of the adduct with CN at b2 or b4 is formed, in addition to adduct with OCH3 at bl.…”