1,3-Dipolar Cycloadditions to Strained Olefins |
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Authors: | Konrad B Becker Martin K Hohermuth |
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Abstract: | The Bredt olefins bicyclo 3.3.1]non-1-ene (2) , bicyclo 4.2.1]non-1 (8)-ene (3) , and bicyclo 4.2.1]non-1 (2)-ene (4) react rapidly with 1,3-dipoles such as diazomethane, phenyl azide, and mesitonitrile oxide to yield mixtures of two regioisomeric cycloadducts 10, 11 and 12 , respectively. On the contrary, cycloaddition to the comparable monocyclic 1-methyl-(E)-cyclooctene (5) is fairly regioselective. 2-Methylnorborn-2-ene (6) gives one isomer with mesitonitrile oxide (as do less strained olefins), but mixtures with diazomethane and phenyl azide. 1H-NMR. and 13C-NMR. spectra of the cycloadducts are reported. The results are discussed in the light of frontier molecular orbital theory. |
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