The silver ion-induced rearrangement of N-chlorocyclobutylamines

The effect of treating N-chlorocyciobutylamlnes with silver tetrafiuoroborate and a subsequent hydride reduction results in moderate yields of substituted pyrroiidines. Ring-expansion in these reactions presumably results in imminium ions which were found not to react with internal carbon-carbon double bond nucleophiles when re arranged in aprotic media. Similar rearrangements of multiply substituted N-chlorocyclobutylamines produced, after reduction, substituted pyrroiidines whose substitution patterns reflected migration of carbon bonds to the electron-deficient nitrogen center. The formation of these products has consistently been shown to be the result of favorable orbital overlap of the empty orbital on nitrogen and a carbon-carbon bond of the cyciobutyl ring. Which bond of this moiety migrates has been suggested to be dependent on which bond can achieve the least sterically crowded transition state in a trans-anti spatial arrangement with the nitrogen-chlorine orbital bonding.