Vinylcyclopropan‐Komplexe und Vinylcyclopropane aus Carben‐Komplexen und 1,3‐Dienen

Abstract

Vinylcyclopropane Complexes and Vinylcyclopropanes from Benzylidene Complexes and 1,3‐DienesBenzylidenepentacarbonyl complexes (CO)5M[C(C6H4R‐p)H] (1) [M – W:RH (a), OMe (b); MCr: R – H (c), OMe (d)], react with cyclopentadiene by stereospecific transfer of the benzylidene ligand to one CC bond of the diene and coordination of the resulting endo;‐6‐arylbicyclo[3.1.0]hex‐2‐ene (4) to the metal. The [CO]5M fragment occupies the exo‐position. Addition of bromide liberates 4 from the metal. The reaction of 1a with 1,3‐cyclohexadiene gives the corresponding (endo;‐7‐phenylbicyclo[4.1.0]hept‐2‐ene)tungsten complex (6) and, after addition of Br−, the free bicyclic compound. The sequential reaction of 1a with 1,2,3,4,5‐pentamethylcyclopentadiene and Br− affords the endo;‐6‐phenyl‐exo;‐4‐methyl isomer of pentamethylphenylbicyclo[3.1.0]hex‐2‐ene 9 with more than 85% stereoselectivity. The benzylidene transfer from 1a to cis‐and trans‐pentadiene, isoprene, and 2‐chloro‐1,3‐butadiene proceeds regiospecifically to the more electron‐rich CC bond to give (E)‐ and (Z)‐phenylvinylcyclopropanes. The E/Z ratio ranges from 0.52 to 2.2. The structures of the complexes 3d and 6 were established by X‐ray analyses.