Abstract
An addition/elimination sequence of selenium halides to pseudo-geminally bis(acetylene) substituted [2.2]paracyclophanes leads to new bridges with an endo-exo-diene substructure. The reactions have been found to be sensitive to the substitution of the ethynyl group. The formation of dienes with a zig-zag configuration is related to that observed for non-conjugated cyclic diynes of medium ring size.
Highlights
Starting with their discovery in 1949, the [2.2]paracyclophane molecule and its derivatives have been intensely studied [1,2,3]
Much attention is being paid to the development of new functionalized [2.2]paracyclophanes that can be used in asymmetric synthesis [8], while the formation of new bridges, functionalized ones, has been somewhat neglected so far
In continuation of our investigations on the intramolecular interaction of chemically disturbed functional groups in pseudogeminally substituted [2.2]paracyclophanes, we report here the results of the addition reactions of selenium halides to pseudogeminal bis(acetylenes)
Summary
Starting with their discovery in 1949, the [2.2]paracyclophane molecule and its derivatives have been intensely studied [1,2,3]. In continuation of our investigations on the intramolecular interaction of chemically disturbed functional groups in pseudogeminally substituted [2.2]paracyclophanes, we report here the results of the addition reactions of selenium halides to pseudogeminal bis(acetylenes). The reaction of 1 with one equivalent of in situ prepared SeBr2 [28], in chloroform at 0 °C, provided a mixture of isomeric cyclic dienes 5 and 6, and the tetrabromo derivative 7 (Scheme 1, Table 1, entry 3) in 76% yield.
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