Free-radical reactions of halogenated bridged polycyclic compounds. Part VI. The addition of ethanethiol and thiophenol to 1,2,3,4-tetrachloronorborna-2,5-diene, 1,2,3,4,7-syn-pentachloronorborna-2,5-diene, and 1,2,3,4,7-anti-pentachloronorborna-2,5-diene

Abstract

The addition of thiols to 1,2,3,4-tetrachloronorborna-2,5-diene (II) affords products derived from both exo- and endo-attack by thio-radicals. A similar situation occurs with 1,2,3,4,7-syn-pentachloronorborna-2,5-diene (IV) which has the same stereochemical features controlling the direction of radical attack. With 1,2,3,4,7-anti-pentachloronorborna-2,5-diene (III), in which stereochemical considerations are similar to those of hexachloro-norbornadiene (I), the products are derived from stereospecific endo-attack. The results indicate that the direction of radical attack on these dienes is controlled by both the bridge and bridgehead chlorines. Establishment of the structures of the rearrangement products formed on addition of ethanethiol and thiophenol to 1,2,3,4,7-anti-pentachloronorborna-2,5-diene (III) as ethyl and phenyl 1,2,3,5-endo, 6-exo-pentachloronorborn-2-en-7-syn-yl sulphides (VIIh and k) supports our earlier deduction that the rearrangement products formed on addition of thiols to hexachloronorbornadiene (I) have the thio-group in the syn-position at C-7 and not the anti-position as has recently been proposed by certain Russian workers.