Lewis‐Acid‐Catalyzed Reactions of Bis(4‐alkoxyphenyl)methanol with (Diarylmethylene)‐ and (Dialkylmethylene)cyclopropanes

Bis(4‐methoxyphenyl)methanol ( 2a ) can be transformed by BF 3 · OEt 2 ‐catalyzed reactions of (arylmethylene)cyclopropanes 1 to the corresponding polysubstituted cyclopentenes 3 as the major products along with methylenecyclobutanes and dienes as minor products. The reaction conditions are mild, yields are moderate to good. In the reactions of aliphatic methylenecyclopropanes with bis(4‐methoxyphenyl)methanol ( 2a ), cyclopentenes 3o – q were produced in good yields under the standard conditions. Interesting results were obtained from the reactions of 1‐[cyclopropylidene(4‐methoxyphenyl)methyl]‐4‐methoxybenzene ( 1e ) with bis(4‐alkoxyphenyl)methanols 2 : polysubstituted cyclopentene derivatives 5 were obtained in good yields under mild reaction conditions. Plausible reaction mechanisms based on the deuterium‐labeling and control experiments are proposed.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)