109. The Intramolecular Ramberg-Baecklund Reaction: A Convenient Method for the Synthesis of Strained Bridgehead Olefins

Article abstract of DOI:10.1002/hlca.19830660412

The stereochemical aspects of the intramolecular Ramberg-Baecklund reaction, i.e. the 1,3-elimination of hydrogen halide followed by sulfur dioxide extrusion, have been studied on the α-bromosulfones of the 1-thiadecalin series.Whereas the cis,exo-bromosulfone 23a containing the ideal W-type arrangement of the reacting atoms undergoes a clean Ramberg-Baecklund reaction, the trans,exo- and trans,endo-bromosulfones, 24a and 24b, respectively, lead to an α,β-unsaturated sulfone by simple 1,2-elimination of HBr.Application of the Ramberg-Baecklund reaction to 9-bromo-8-thiabicyclo<5.2.1>decane-8,8-dioxide (17) permits a short synthesis of the Bredt olefin bicyclo<5.1.1>non-1(8)-ene (5), which can be isolated but shows the typical high reactivity of other methylene-bridged (E)-cyclooctenes.