A NEW CYCLOPENTADIENE AND ITS USE AS A LIGAND FOR CATALYTICALLY ACTIVE RHODIUM COMPLEXES

Dimethyl -methoxycarbonylcyclopenta-1,3-diene-1,2-diacetate has been p repared from benzyl methyl malonate by reaction with 2-propynyl bromid e, followed by palladium-catalyzed ring-forming oxidative carbonylatio n and by elimination of the benzyloxycarbonyl group and double bonds i somerization. The anion of the diacetate readily reacts with transitio n metal complexes, to give the corresponding cyclopentadienyl derivati ves. We describe here some complexes, obtained from [{RhCl(L)(2)}(2)] [L = CO, C2H4, or 1,5-cyclooctadiene (COD)], which are efficient catal ysts for the alkyne-nitrile co-cyclization to pyridines and for the hy droformylation of styrene and 1-hexene.