Unexpected formation of 4-arylcyclopentane-1,1,3,3-tetracarboxylates in GaCl3-catalyzed reaction of 2-arylcyclopropane-1,1-dicarboxylates with tetrasubstituted 1-pyrazolines

Gallium trichloride-catalyzed reaction between 2-arylcyclopropane-1,1-dicarboxylates and 3,3,5,5-tetrasubstituted 1-pyrazolines affords 4-arylcyclopentane-1,1,3,3-tetracarboxylates, which originate from cycloaddition of the two molecules of the starting cyclopropane with the loss of one arylidene fragment subtracted by the 1-pyrazoline.