Carbonium ions norbornene

The carbonium ion rearrangements that can be observed in halofluonnations are illustrated by the reactions ot norbornene (Table 2) and norbornadiene (Table 3). Product ratios may vary with the different reagent combinations... 

The solvolysis of exo-norbornyl brosylate in acetic acid gives 4% elimination products, 98% of which is nortricyclene and only 2% is norbornene. The larger yield of the cyclopropane than the olefin was quoted as support for a non-classical rather than a rapidly equilibrating pair of classical carbonium ions . ... 

Reaction of e J<9-5-hydroxymethyl-2-norbornene with dichlorocarbene generated under phase transfer conditions leads to 3-chloro-5-oxatricyclo-[5.2.1.0 ]-dec-2-ene as the major product (see Eq. 2.21). Formation of this product probably involves initial addition of dichlorocarbene to the carbon-carbon double bond to yield a 1,1-dichlorocyclopropane which ionizes and ring-opens to form a chloro-substituted allylic carbonium ion. This cation is then trapped by the intramolecular nucleophilic alcohol [40]. 

The stereospecific trans addition to norbornene is a particularly interesting reaction. Neither carbonium ion rearrangements nor the syn addition seen with many other electrophilic reagents is observed. These results, which are indicative... 

Brown, H. C., and K.-T. Liu Additions to Bicyclic Olefins. VII. Electrophilic Addition of Hydrogen Chloride and Deuterium Chloride to Norbornene, 2-Methyl-norbornene, and Related Bicyclic Olefins. Evidence for a Carbonium Ion Process and the Capture of Unsymmetrical (Classical) 2-Norbornyl Cations. J. Amer. Chem. Soc. 97, 600 (1975). 

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