Photocatalysis-VII. Photochemical cyclodimerisation of cycloalkenes catalysed by copper(I) triflate. Formation and identification of two cycloheptene and five cyclooctene dimers
article
The photochemical cyclodimerisation of cycloheptene and cyclooctene has been studied under irradiation at 254 nm, using copper(I) triflate as catalyst. Two cycloheptene dimers cis-anti-cis- and trans-syn-trans-tricyclo [7.5.0.02,8] tetradecane and five cyclooctene dimers (all stereoisomeric tricyclo [8.6.0.02,9] hexadecanes) have been obtained. The 1H and 13C NMR spectra of the cyclooctene dimers show an upfield shift (from 2.4 to 1 ppm) of the cyclobutyl hydrogens due to cyclobutane ring puckering and a downfield shift of the cyclobutyl carbon resonances. Their GC retention times decrease upon increased ring puckering. The photocatalysed dimerisation of cycloheptene is exceptional in that no trans-anti-trans or cis-trans isomers are formed as is the case for cyclohexene or cyclooctene. Thermally, the trans-cycloheptene ligand in the copper(I) triflate complex cyclotrimerizes exclusively, via R,R,R- or S,S,S-combinations. ?? 1982.
TNO Identifier
229284
ISSN
00404020
Source
Tetrahedron, 38(9), pp. 1311-1319.
Pages
1311-1319
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