51319-08-5Relevant academic research and scientific papers
Photochemistry of Cycloalkenes. 9. Photodimerization of Cyclohexene
Kropp, Paul J.,Snyder, John J.,Rawlings, Peter C.,Fravel, Harold G.
, p. 4471 - 4474 (1980)
The photodimerization of cyclohexene has been restudied.Either direct or triplet-sensitized irradiation produced a stereoisomeric mixture of dimers 6-8, respectively, as primary products with the cis,trans isomer 7 predominating.The direct-irradiation process was complicated by the accompanying formation of the radical-derived products 3-5.Dimerization is interpreted in terms of initial light-induced cis-trans isomerization of cyclohexene, followed by a nonstereospecific ground-states + 2a>addition of trans-cyclohexene to the cis isomer.By contrast, cycloheptene showed little tendency to undergo photodimerization; attempted p-xylene-sensitized dimerization afforded instead principally the sensitizer-olefin adducts 10 and 11.Comparison is made with the copper(I) triflate catalyzed photodimerization of cyclohexene and cycloheptene.
Enantiodifferentiating photocyclodimerization of cyclohexene sensitized by chiral benzenecarboxylates
Asaoka, Sadayuki,Horiguchi, Hisashi,Wada, Takehiko,Inoue, Yoshihisa
, p. 737 - 747 (2007/10/03)
The photosensitized cyclodimerization of (Z)-cyclohexene (1Z) was performed over a range of temperatures in the presence of chiral benzene(poly)carboxylate sensitizers, giving trans-anti-trans-, cis-trans- and cis-anti-cis[2 + 2]- cyclodimers 2-4. Of the two chiral cyclodimers (2, 3), only 2 was obtained optically active with enantiomeric excesses as high as 68.3% at -78°C, whereas 3 was consistently racemic under various reaction conditions employed. The detailed reaction mechanism and the origin of enantiodifferentiation have been elucidated and involve the initial enantiodifferentiating photoisomerization of 1Z to the highly reactive (E)-isomer (1E) and the subsequent stereospecific concerted cyclodimerization with 1Z giving optically active 2 which is competing with the non-stereospecific stepwise cyclodimerization to racemic 2 and 3.
