The remarkable transformation of fused-ring norbornene bridgemethylene alcohols into a product identified by X-ray diffraction as containing the novel tetracyclo[5.3.1.0.0]undecene system

Abstract

Treatment of anti- and syn-epimers (1) and (2) of exo-endo-3,4,5,6-tetrachlorotetracyclo [6.2.1.1^3,6.0^2,7]dodeca-4,9-dien-11-ol with H₂SO₄–CCl₄ gives besides the previously recognised tetrachloropentacyclododecanone (3) small but significant amounts of 1,3,4,11-tetrachloro-2-formyltetracycio[5.3.1.0^2,6O.^5,9]undec-3-ene (12), an apparently novel ring system derived by a new rearrangement sequence. The structure of tetrachlorotetracycloundecene (12) follows from the X-ray crystal structure of the methanesulphonate (14) of its simple 2-hydroxymethyl reduction product. ¹H and ¹³C n.m.r. characteristics of (12), its various deuteriated analogues, and their synthesis are discussed.