Bicyclic carbo- and heterocycles from an allylidene complex and cyclic 1,3-dienes by tandem cyclopropanation/cope rearrangement

Abstract

The allylidene complex (CO) 5WCHC(Ph)C(Ph)H ( 4) reacts with cyclopentadiene by stereospecific transfer of the carbene ligand to one of the two double bonds of cyclopentadiene to give a cis-divinylcyclopropane complex 5. The divinylcyclopropane ligand coordinates to the metal via the unsubstituted double bond. Addition of bromide to solutions of 5 gives rise to the formation of [(CO) 5WBr] − and a bicyclo[3.2.1]octadiene ( 6), the Cope rearrangement product of the free divinylcyclopropane. Thermolysis of 5 affords 6 and its (CO) 5W complex. The reaction of 4 with furan ( 8a), 2-methylfuran ( 8b) and 3-methylfuran (8c) affords the (CO) 5W(bicyclo[3.2.1]oxahepta- diene) complexes ( 9a– c), The formation of 9a– c which is chemo-, regio- and stereospecific is explained by a tandem cyclopropanation/Cope rearrangement sequence. The bicyclic ligands 10a– c are liberated from the metal either by thermolysis of solutions of 9a– c or by addition of bromide.