Reaction of norbornadiene with a mixture of 1,1-dichloroethylene, sulphuric acid, and boron trifluoride–ether complex

Abstract

The reaction of norbornadiene with a mixture of 1,1-dichloroethylene, sulphuric acid, and boron trifluoride–ether does not give the expected dicarboxylic acids. The major product is a neutral fraction containing tricyclo[2.2.1.0^2,6]heptan-3-yl chloride, 2-exo,7-syn-dichloronorbornane, 2-exo,5-endo-dichloronorbornane, and 2-exo,5-exo-dichloronorbornane. An additional product is an acid lactone thought to be 5-exo-carboxymethyl-6-endo-hydroxynorbornan-2-endo-ylacetolactone. The formation of the dichlorides is suggested to involve the norbornenyl and chloronorbornyl carbonium ions; other potential sources of these ions lead to similar mixtures of dichlorides. The neutral fraction from the reaction with norbornene contains some 2-exo-chloronorbornane.