Bingel-type reaction

The usefulness of the retro-cyclopropanation reaction is even more remarkable than previously anticipated. It was questioned whether this reaction allowed the selective removal of a Bingel-type addend while leaving addends of a different type unaffected. A variety of mixed bis-adducts such as those shown in Fig. 29, were prepared, all of which contained a bis(ethoxycarbonyl)methano group [182]. In all cases, CPE led to the selective removal of the Bingel addend in over 60% yield, while the other one was retained, confirming that the reaction may be used in a synthetic protection-deprotection protocol to prepare novel fullerene derivatives. 

However, the chemical reduction reaction does not work efficiently for the removal of two Bingel addends, whereas the electrochemical reduction process works very efficiently. One of the most interesting examples that illustrates the difference between the chemical and electrochemical methodologies involves the cyclophane type trans-1 ( -37) conjugate [76], The chemical reductive protocol fails completely with this compound, presumably due to ion complexation by the crown ether group and consequent stabilization. When the electroreductive method was used, a clean retrocyclopropanation reaction was observed (Figure 25). 

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