Further reactions of nucleophiles with some chlorine-substituted norbornadienes

Abstract

The reaction of 1,2,3,4,7-syn-pentachloronorborna-2,5-diene with ethoxide ions results in a 3:5 mixture of products derived from replacement of a vinylic chlorine atom and from addition to the unsubstituted double bond. The 7-anti-isomer and 1,2,3,4-tetrachloronorborna-2,5-diene afford only products of reaction at the chlorine-substituted double bond. The 5-phenyl derivatives of these dienes react with sodium methoxide in methanol to afford the products of the addition of methanol to the phenyl-substituted double bond. Reaction occurs at both double bonds when hexachloronorbornadiene is treated with sodium methanethiolate in ethanol. 5-Methylhexachloronorbornadiene is isomerised to hexachloromethylenenorbornene on treatment with sodium methoxide in methanol; with dimethylformamide as solvent further reaction occurs at the chlorine-substituted double bond of the isomerised diene. The results are interpreted in terms of a series of finely balanced factors controlling product formation.