The catalysis of a reaction of 4,4-dicarbomethoxy-1-cyclopropyl-1,6-heptadiene and HSiMe OSiPh t-Bu by a 1:1 mixture of (phen)Pd(Me)Cl (phen = 1, 10-phenanthroline) and NaBAr [Ar = 3, 5-C H (CF ) ] in Ch Cl at 0° C for 12 h was presented. The (E)-trans-3-(1-butenyl)-4-(3-tertbutyl-1,1-dimethyl-3,3-diphenyldisiloxymet hyl)-1,1-dicarbomethoxycyclopentane in 93% isolated yield as a 25:1 mixture of isomers was formed by the catalysis. The generation of active cationic palladium catalyst in situ from mixtures of (phen)Pd(Me)Cl and NaBAr [Ar= 3,5-C H (CF ) ] was also observed. 2 2 4 6 3 3 2 2 2 4 6 3 3 2