Cloke rearrangement

Scheme 45. Preparation of heterocycles 138,141 via Cloke rearrangement of the cyclopropyl-ketimine moieties in 131,135 [60b]...

Cyclopropylimines can be transformed to dihydropyrrols by heating with catalytic amounts of acids having nucleophilic anions (Cloke rearrangement " ). It is very likely that this ring expansion involves an acid-assisted nucleophilic attack followed by reclosure to the heterocycle as depicted in equation 28. 

A promising alternative to generate cyclopropyl iminium ions, the presumable first intermediates in the Cloke rearrangement, is outlined in equation 32. The enammonium salts have been obtained at room temperature after treatment with lithium bromide in acetonitrile. These very mild conditions should be compatible with many sensitive functional groups. 

CLOKE - WILSON Cyclopropylkelone Rearrangement Rearrangement o( cyclopropyl ketones or imines to dihydnofurans or dihydropyrroles, thermally, photochemically, or by Lewis adds... 

CLEMMENSEN Reduction 88 CLOKE - WILSON Rearrangement 69 Cohen 385... 

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