Photochemical Approach to New Polycyclic Substrates Suitable for Further Photocatalytic Functionalization

New polycyclic compounds are synthesized by photocycloaddition reactions of methoxy, methyl or phenyl substituted butadiene derivatives 11−14. Mono- and dimethoxy butadiene derivatives 11 and 12 undergo intramolecular [2+2] photocycloaddition giving benzobicyclo[3.2.1]octadiene structures (endo-15, endo,trans-17) as main products. As minor photoproducts tricyclic compounds endo-16 and endo,trans-18 are isolated, respectively, formed by [4+2] photoinduced cycloaddition of the starting molecules. The reaction of compounds 13 and 14 is more selective and only benzobicy-clo[3.2.1]octadienes endo,endo-19 and endo,endo-20 are formed, respectively. New bicy-clo[3.2.1]octadienes with isolated double bond can be suitable substrates for further efficient photo-catalytic oxygenations in course of new functionalized polycycles, potentially new biologically active compounds

Photochemical approach to functionalized benzobicyclo[3.2.1]octene structures via fused oxazoline derivatives from 4- and 5-(o-vinylstyryl)oxazoles

Novel cis/trans-4- and cis/trans-5-(2-vinylstyryl)oxazoles have been synthesized by Wittig reactions from the diphosphonium salt of α, α’-o-xylene dibromide, formaldehyde and 4- and 5-oxazolecarbaldehydes, respectively. In contrast, trans-5-(2- vinylstyryl)oxazole has been synthesized by the van Leusen reaction from trans-3-(2-vinylphenyl)acrylaldehyde which is prepared from o-vinylbenzaldehyde and (formylmethylene)triphenylphosphorane. The 4- and 5-(2-vinylstyryl)oxazoles afford, by photochemical intramolecular cycloaddition, diverse fused oxazoline-benzobicyclo[3.2.1]octadienes, which are identified and characterized by spectroscopic methods. The photoproducts formed are relatively unstable and spontaneously or on silica gel undergo oxazoline ring opening followed by formation of formiato- or formamido-benzobicyclo[3.2.1]octenone derivatives. On irradiation of 4-(2-vinylstyryl)oxazole small quantities of electrocyclization product, 4-(1, 2-dihydronaphthalen-2-yl)oxazole, are isolated and spectroscopically characterized

Synthesis and Photochemistry of Styryl Substituted Annelated Furan Derivatives. IV. Concentration Directed Intra- and/or Intermolecular [2+2] Cycloaddition

New cyclobutane derivatives have been synthesized by intermolecular photochemical [2+2] ethene-ethene »head-to-head« (9a,b) and »head-to-tail« (10a,b–11a,b) as well as [2+2] ethenefuran (12a,b) cycloaddition from 2-[2-(2-vinylphenyl)ethenyl]benzo[b]furan (2a) and 2-[2-(2-methylphenyl)ethenyl]benzo[b]furan (2b), respectively. All compounds were isolated and characterized by spectroscopic methods. Under the benzene solution irradiation of 5 × 10-1 mol dm-3 concentration and higher, 2-[2-(2-vinylphenyl)ethenyl]benzo[b]furan (2a) gave only dimeric products (9a–12a). At the 1 × 10-1 mol dm-3 concentration, a mixture of dimers (9a–12a) and 7,12-dihydro-7,12-methano-6H-benzo[4,5]cyclohepta[1,2-b]benzofuran (5) was formed in a ratio 2:1

Photochemical and Thermal Transformations of Thiophene o-Distyrylbenzene Analogues in Acidic Media

Intramolecular photochemical reactions of thiophene analogues of o-distyrylbenzene, 2,2'-(o-phenylenedivinylene)dithiophenes (1a,b), 3,3'-(o-phenylenedivinylene)dithiophene (2a) and 3,3'-(o-phenylenedivinylene)dibenzothiophene (2b), were studied in acidic media at low concentrations. A 1,6- and 1,5-ring closure of hexatriene system leading to dihydronaphthalene or indene derivatives, respectively, was observed

Functionalization of the benzobicyclo[3.2.1]octadiene skeleton possessing one isolated double bond via photocatalytic oxygenation

Photocatalytic oxygenation of three phenyl derivatives of a bicyclic skeleton with a free double bond 1a, 1b and 1c were carried out by utilizing a cationic and an anionic manganese(III) porphyrin irradiated in the visible range. While photocatalysis of 1a and 1b led to the formation of the corresponding hydroperoxy derivatives 2 and 3, respectively, (besides unidentified high-molecular-weight products) in the presence of the anionic Mn(III) porphyrin, the cationic photocatalyst proved to be less efficient and less selective with 1a. In the case of 1b, also with the cationic porphyrin, the corresponding hydroperoxy derivative (3) was the main product at a shorter reaction time (2h), whereas a longer irradiation (4h) led to the significant formation of a keto derivative (5) with a hydroperoxy substituent and a free double bond at positions deviating from those in the previous products (2 and 3). A dramatic change in the reactivity was observed for the methoxy derivative (1c). It gave only traces of identifiable products by using the anionic photocatalyst, while application of the cationic Mn(III) porphyrin resulted in a relatively efficient formation of an epoxy derivative (6) due to the reaction of the isolated double bond

Photochemistry of p-(5-Substituted-2-furyl)-o-divinylbenzenes; Substituent Effects on the Reaction Course

Irradiation of 2-[2-(2-vinylphenyl)ethenyl]furan (la) and 5-methyl- 2-[2-(2-vinylphenyl)ethenyl]furan (lb) gave 9,10-đihydro-4,9-me- thano-4ff-benzo[4,5]cyclohepta[l,2-6]furan (2a) and 9,10-dihydro- 2-methyl-4,9-methano-4H-benzo[4,5]cyclohepta[l,2-b]furan (2b), respectively, in a very good yield in addition to traces of 5. Contrary to these results, the 5-substituted furan derivatives 1 (c: R = CN; d: R = P-C6H4CH3, e: R = OCH3) gave mainly, upon irradiation under the same conditions, isomerization about the double bond, high-molecular-weight products, small amount of phenanthrenes 5 and only traces of bicyclic structure 2