On the Mechanism of Ionic 1,3-Elimination in the Formation of Halonortricyclones

Abstract

<p>The mechanism of 1,3-elimination in the bicyclo(2,2,1)heptyl system was studied using mass spectrometry and gas chromatography. The ionic chlorination, bromination, and iodo monochlorination of 2,3-d₂-norbornene, exo, exo-5, 6-d₂-norbornene, and endo, endo-5, 6-d₂-norbornene were performed to obtain deuterium loss data. In the chlorination of norbornene, most of the tricyclic product arises from the cyclic norbornyl chloronium ion and/or classical exo-S-chloronorbornyl cation (classical ion interpretation), or from the cyclic norbornyl chloronium ion (non-classical ion interpretation). In the bromination of norbornene, most of the tricyclic product arises from the classical syn-7-bromonorbornyl cation and/or anti-7-bromonorbornyl cation (classical ion interpretation), or from the first formed non-classical 3-bromonorbornyl cation (non-classical ion interpretation). In the iodo monochlorination of norbornene, most of the tricyclic product arises from the classical syn-7-iodo-norbornyl cation (classical ion interpretation), or from the first formed non-classical 3-iodonorbornyl cation (non-classical ion interpretation. Three of the products from the reaction of norbornene with iodo monochloride were isolated and identified to be: 3-iodonortricyclene, exo-2-iodo-endo-3-chloronorbornane, and syn-7-iodo-exo-2-chloronorbornane.</p>