The fragmentation of 7-norbornyloxychlorocarbene — SNi-like transition states

Abstract

7-Norbornyloxychlorocarbene (15) fragments mainly to 7-norbornyl chloride (16). A C-2 deuterated analog of 15 (syn-15-d) fragments to labeled chloride 16 with 78% retention and 22% inversion. When the deuterium label is replaced by a syn-exo-2-methyl group, the resultant carbene 22 fragments to syn- and anti-7-chloro-exo-2-methylnorbornane in a ratio of 1:1.1, corresponding to 48% retention and 52% inversion. Computational studies suggest that the fragmentations proceed via competitive SNi-like transition states that lead to either retention or inversion. Key words: carbenes, carbocations, SNi reactions, stereochemistry.