Nucleophilic addition and substitution reactions of polyhalogenated norbornadienes with alkenoxide and alkenoxide anions. A novel Claisen rearrangement of allyl norbornadienyl ethers

Abstract

Rational syntheses of polyhalogenonorbornadienes (including the hepta- and octa-chloro-compounds and their bromo- and dibromo-hexachloro-analogues) and their reactions with alkoxide and alkenoxide anions in the presence (or otherwise) of dipolar aprotic solvents are described. Vinylic chlorine or bromine substitution, together with addition of alcohols appear to be the more important of their reations with these bases. Hydrolysis of the resulting divinylic ethers gives polyhalogenonorbornane-2,5-diones exhibiting unusual Iong-range n.m.r. spin couplings. Mild thermolysis of the derived allyl vinyl ethers results in Claisen [3,3] sigmatropic rearrangements new to the norbornadienes. Comment is made on the stereochemistry of this rearrangement and on addition reactions of norbornenes.