Substituted endo-Tricyclo[3,2,1,0^2,4]oct-6-enes. I. Preparation by the Diels-Alder reaction between cyclopropene and substituted cyclopentadienes

Abstract

The Diels-Alder reaction between cyclopropene and substituted cyclopentadienes has been used to prepare several chloro- and chloromethoxy-substituted endo-tricyclo[3,2,1,0^2,4]oct-6-enes. In the presence of base, the reaction of 1,2,3,4-tetrachlorocyclopentadiene with cyclopropene yielded the expected adduct together with adducts arising from the isomeric 1,2,3,5- and 1,2,4,5-tetrachlorocyclo- pentadienes. Subsequent isomerization during workup of the adduct, 1,6,7,anti-8-tetrachloro-endo-tricyclo[3,2,1,0^2,4]oct-6-ene, afforded endo-4,6,7,8-tetrachlorotricyclo[3,3,0,0^2,8]oct-6-ene. The relatively unreactive methoxy-substituted cyclopentadienes yielded adducts of cyclopropene together with adducts of 3-cyclopropylcyclopropene (cyclopropene dimer). Structural assignments of adducts were based predominantly on p.m.r. data which will be discussed in greater detail in a later publication.