FREE-RADICAL ADDITION OF IODO-F-ALKANES TO ISOMERIC 5-NORBORNENE-2,3-DICARBOXYLIC ACID-DERIVATIVES

Free-radical addition of linear iodo-F-alkanes (RFI) to isomeric 5-norbornene-2, 3-dicarboxylic acids and derivatives occurred stereoselectivey. The anhydrides gave trans addition of RFI exclusively/while exo-cis addition was the principal mode of reaction of endo-2, 3-dicarboxylic esters. Nonstereoselective addition of the branched 2-F-propyl iodide took place as the result of steric crowding in the intermediate radical. Azonitrile, peroxide, or ultraviolet initiation was used as required. Chemical transformation of the resulting adducts was profoundly affected by their structure, particularly by the position of the iodine atom. Heating of exo-6-iodo-exo-F-alkyl-2, 3-norbornanedicarboxylic esters gave a lactone, with loss of alkyl iodide; the endo-6-iodo compounds remain unchanged. Similarly, base-induced cyclization of the endo-6-iodo derivatives to a nortricyclene product took place and the endo-6-iodo isomer again was unaffected. This stereospecificity sheds new light on these reactions. Spectroscopic properties of these F-containing compounds were extensively studied, and a newarea of derivative chemistry was opened. © 1979, American Chemical Society. All rights reserved.