Dichlorocyclopropanes from olefins and

Enamines are readily formed from ketones and therefore constitute an accessible class of substituted olefins. The dichlorocyclopropanation reaction of enamines has not been a preparatively useful one in the past. However, when the reaction is conducted under phase transfer conditions, moderate to excellent yields of the dichlorocarbene adducts can be obtained [34, 35]. A variety of enamines have been subjected to phase transfer cyclopropanation and the results are recorded in Table 2.3. 

Cyclopropanation of alkenes carrying electron-withdrawing groups with dihalo-carbenes does not take place under the normal reaction conditions unless the dihalocar-bene is generated from trihalomethylphenylmercury compounds. By this procedure acrylonitrile was converted into l-cyano-2, 2-dichlorocyclopropane in 78% yield and other acrylic derivatives are transformed into dichloromethyl cyclopropane carboxylates (186) (equation 46). Treatment of electron-deficient olefins with dibromomethane in the presence of Ni(0) complex/Zinc/Lewis acid seems to be very effective for cyclopropanation. ... 

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