1,3-Dilithio-2-(diphenylmethylene)propane

The reaction of 2,2-diphenylmethylenecyclopropane (5) with an excess of lithium and a catalytic amount of DTBB (4 mol %) in THF at −78 °C leads to the formation of dilithiated species 6–8 by reductive opening of the cyclopropane ring. Further reaction of these intermediates with different electrophiles [E = H2O, D2O, CH2CMeCH2Cl, Me3SiCl, Me3SiCH2Cl, t-BuCHO, Me2CO, Et2CO, n-Pr2CO, i-Pr2CO, t-Bu2CO, (CH2)5CO, Ph2CO and adamantanone] is highly regioselective, yielding exclusively the corresponding products 9, after hydrolysis with water. However, when 3-chloro-2-(chloromethyl)propene (14) is used as a dielectrophile, the cyclisation to give a six-membered ring takes place through intermediate 6, giving compound 16 as the only reaction product.

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