Note on the Synthesis of 1, 1-Dichloro-2, 3-divinylcyclopropane and Other Functionalized Dichlorocyclopropanes

The title compound 1 was synthesized via addition of dichlorocarbene to dimethyl trars-3-hexenedioate ( 5 ), using o-nitrophenylselenic acid-elimination to form the double bonds. Reaction of dichlorocyclopropane 8 with ozone on silica gel furnished the monoketone 10 ; no diketone 11 could be isolated upon further exposure of 10 to O₃/SiO₂. When the bis(p-toluenesulfonate) 13b was treated with t-BuOK, 16 was obtained in low yield as the only isolable product. It is believed to arise from Cope-rearrangement of an intermediate cis-divinylcyclopropane 14 to cycloheptadiene 15 , which undergoes a subsequent allylic rearrangement to 16 .