S N i fragmentations of alkoxychlorocarbenes – a perspective

After a review of the early literature concerning S N i fragmentations of alkyl chlorosulfites and chloroformates, we present experimental and computational results for the S N i fragmentations of alkoxychlorocarbenes. Examples include cyclohexyloxychlorocarbene, 7‐norbornyloxychlorocarbene, 3‐nortricyclyloxychlorocarbene, exo ‐5‐norbornenyl‐2‐oxychlorocarbene, and endo ‐5‐norbornenyl‐2‐oxychlorocarbene. Computations generate a ‘family’ of closely related charge‐separated S N i structures which approximate asynchronous, polar, concerted transition states and tight, short‐lived ion pair intermediates. The precise description and behavior of these species in a given reaction depends on the identities of the alkyl group, the potential counterion, and the solvent. Copyright © 2007 John Wiley & Sons, Ltd.