Pd(O) Promoted Transformation of 1,1‐Dialkoxycarbonyl‐2‐(1,3‐butadienyl)cyclopropanes into 2‐Ethenyl‐3‐cyclopentenes

1,3‐Butadienylcyclopropanes activated by two electron‐withdrawing groups ( 1 ) smoothly rearrange to vinylcyclopentene derivatives in the presence of a Pd(O) catalyst under mild conditions. For example, dimethyl 1,3‐butadienylcyclopropane‐1,1‐dicarboxylate 1a reacts with 3 mol% Pd(PPh 3 ) 4 in DMSO at 25–60 °C for 30 min to provide dimethyl 2‐ethenyl‐3‐cyclopentene‐1,1‐dicarboxylate 2a in 87% yield. Other data show that the new method is useful in the synthesis of cyclopentene derivatives including dolichodial and iridodiol.