Some photochemical rearrangements of vinylcyclopentadienes. Mechanistic and exploratory organic photochemistry

Abstract

. Can. J. Chem. 62, 2592(1984. The photochemistry of 2,3-diphenyl-1,4,5-trimethyl-5-vinylcyclopentadiene and 1,2-diphenyl-3,4,5-trimethyl-5-vinylcyclopentadiene was studied. The triplet of the 2,3-diphenyl isomer was found to undergo a 1,s-vinyl migration; in contrast, the 1 ,2-diphenyl diene was unreactive. On direct irradiation, in addition to vinyl migration, four photoproducts were formed from the cyclopentadienes. These were shown to be 5,6-diphenyl-1,2,7-trimethylbicyclo[3. On a CtudiC la photochimie du diphCnyl-2,3 trimkthyl-1,4,5 vinyl-5 cyclopentadikne et du diphCnyl-1,2 trimkthyl-3,4,5 vinyl-5 cyclopentadikne. On a trouvC que 1'Ctat triplet de l'isomkre diphCny1-2,3 subit une migration 1,s du vinyle; par opposition, le diphCnyl-1,2 dikne n'est pas rkactif. Par irradiation directe, les cyclopentaditnes conduisent, en plus du produit de migration du groupe vinyle, ?I quatre photoproduits; on a dCmontrC qu'ils ont les structures suivantes: diphtnyl-5,6 trimCthy1-1,2,7 bicyclo[3.2.0] heptadikne-2,6; diphCnyl-1,s trimCthy1-2,6,7 bicyclo[3.2.0] heptaditne-2,6; diphtnyl-6,7 trimCthyl-1,2,5 bicyclo Introduction One of our main research objectives has been the elucidation of new photochemical organic reactions. It is clear that the number of ground state organic reactions is immense, a result of a century and a half of intensive efforts. In comparison, the number of photochemical reactions is minuscule. Nevertheless, the known photochemical reactions are often fascinating, primarily because of their departure from intuitive ground state expectation, and promising, primarily because patterns of behavior demonstrate the presence of understandable mechanistic factors.In recent years we have uncovered some unique rearrangements of vinylcyclopropenes affording cyclopentadienes (lc, 2; note also work by Padwa et al. (3)). We thus proceeded to investigate the photochemical behavior of the homologous vinylcyclopentadienes.

Nitric Oxide Donors: Chemical Activities and Biological Applications

“…Compound 42 has been extensively used as a triplet quencher. [440][441][442][443][444][445][446][447][448][449][450][451] Recently, the biological activity and NO release mechanism of DD have been studied. Diazetine dioxides are prepared by the oxidation of the corresponding bishydroxyamines with NaOBr in aqueous base.…”

“…It has a lower triplet energy than dienes and does not react through its triplet state. Compound 42 has been extensively used as a triplet quencher. − Recently, the biological activity and NO release mechanism of DD have been studied. Diazetine dioxides are prepared by the oxidation of the corresponding bishydroxyamines with NaOBr in aqueous base. − 3-Bromo-3,4,4-trimethyl-3,4-dihydrodiazete 1,2-dioxide ( 43 ) and 3-bromo-4-methyl-3,4-hexamethylene-3,4-dihydro-diazete 1,2-dioxide ( 44 ) are commercially available.…”