Photosensitized cyclodimerization of phenyl vinyl ethers

Abstract

4-Vinylphenanthrene.-A mixture of 175 mg of methyltriphenylphosphonium bromide, 0.25 ml of 1.91 M phenyllithium, and 20 ml of dry ether were stirred and refluxed under nitrogen for 0.5 hr. A solution of 100 mg of 4-phenanthrenecarboxaldehyde in 20 ml of ether was added drop wise over a period of 15 min, and the mixture was then stirred and refluxed for 2 hr. The reaction mixture was filtered, the filtrate diluted with 200 ml of ether, washed with water, dried, and filtered, and the ether removed in vacuo.The residue was chromatographed on alumina using hexane as the eluent to give an oil which was further purified and analyzed via the picrate: 125 mg (59.1% yield), mp 112-113°.

Carbon–Carbon Bond Forming Reactions via Photogenerated Intermediates

“…Another widely employed approach for the formation of four-membered rings is the [2 + 2] photocycloaddition of alkenes initiated by a SET process. , The reaction has been applied both to electron-rich ( 31 ) and electron-poor ( 30 ) alkenes, as shown in Scheme , and both cyclodimerizations (by using a single alkene) and cross cycloadditions between two different olefins have been carried out. Indeed, the cyclodimerization of phenyl­(aryl) vinyl ethers has been studied under both homogeneous , and heterogeneous , conditions.…”

Electron-transfer-induced photoadditions of the silyl amine, Et2NCH2SiMe3, to .alpha.,.beta.-unsaturated cyclohexenones. Dual reaction pathways based on ion pair-selective cation-radical chemistry

“…In an earlier communication,17 the preliminary results of studies exploring the program outlined above were reported. Observations made in that study and in our continuing efforts have demonstrated (14) In recent (unpublished) studies we have found that intramolecular silyl amine-enone systems undergo SET-induced photocyclization under direct and SET-sensitized conditions. (15) Enone-amine additions of this type in charge affinity terms correspond formally to additions of fl-keto anions to -amino cations or of a-amino carbanions to enones.…”

Synthetic Aspects of Photochemical Electron Transfer Reactions

“…Intervention of either of these electron transfer steps would lead to termination of the chain processes. A variety of other olefin cycloadditions have been uncovered as illustrated by production of the homo-dimers 466(337) and 467, (338,339) Cyclobutane cycloreversions to olefins can be performed under electron transfer sensitized conditions. Pac and co-workers (344) have shown that the indene dimer 470 undergoes a cycloreversion to indene in yields of 75% to 80% by means of a redox photosensitization.…”