Chiral exo-Alkylidenecyclopentanes from (1S,4R)-7,7-Dimethyl-1-vinylbicyclo[2.2.1]heptan-2-one

(1S,4R)-7,7-Dimethyl-1-vinylbicyclo2.2.1]heptan-2-one oxime in the system (CF₃CO)₂O-CF₃COOH and (1S,4R)-1-(1,2-dibromoethyl)-7,7-dimethylbicyclo2.2.1]heptan-2-one in the system MeONa-MeOH undergo fragmentation to give exo-alkylidenecyclopentane derivatives, (4R)-4-cyanomethyl-5,5-dimethyl-1-(1E)-trifluoroacetoxyethylidene]cyclopentane and isomeric (4R)-4-carboxymethyl-1-(1ZE)-2-methoxyethylidene]-5,5-dimethylcyclopentanes, respectively. The trifluoroacetate derivative undergoes unusual rearrangement, yielding an equilibrium mixture of two isomers with endo- and exocyclic double bond.