Via a Homolysis-Coupling Mechanism

When X is an iminium group, the reaction is spontaneous even at —60°C, whereas with the trichloromethyl group it occurs only upon heating to 60-100 °C. When X is not electron-withdrawing, the reaction does not occur. 

13 [19], The 1,3-dichlorinated compounds 8 are bis-electrophilic synthons of great use in heterocyclic chemistry [4b, 20], 

0 X 10 s ) [27], so that cyclopropylmethyl radical 32a is kinetically stable only below -140°C. Captodative substitution has a remarkable stabilizing effect the radicals 32b-e are kinetically stable up to room temperature [17a]. This observation is related to the use of the captodative effect to carry out radical cyclization reactions which are otherwise not kinetically favored (c/ Sec. 3.3.5.3). 

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