Cyclobutene reacted with dibromocarbene in solution to give 1,5-dibromocyclopent-1-ene (9), 1,2,6, 6-tetrabromobicyclo[3.1.0]hexane (10), and 1,2,3,6-tetrabromocyclohex-1-ene (11), in a ratio of 1:4:8, respectively. Compounds 10 and 11 were found to be formed from a second carbene addition and rearrangement under the given reaction conditions.
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8.
Crystallographic data (excluding structure factors) for the structure in this paper have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication numbers CCD -234178. Copies of the data can be obtained free of charge upon application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK [fax: +44(0)-1223336033 or e-mail: deposit@ccdc.cam.ac.uk.
9.
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