Optically Active Cyclopentadienyl Ligands from the Chiral Pool, Part 1. The Synthetic Utility of a Camphor-Derived Pentafulvene

Abstract

Abstract Starting from (1R)-(+)-camphor, the reaction with cyclopentadienylmagnesium chloride gave the corresponding tertiary alcohol 1, which was transformed into the optically active pentafulvene 5-(1,7,7-trimethylbicyclo[2.2.1]heptan-2-ylidene)cyclopentadiene (2) by acidcatalyzed water elimination. Deprotonation with tert-butyllithium yielded the corresponding lithium 5-{(1R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-en-2-yl}cyclopentadienide (3), which was converted into the non-racemic 1,1β-bis{(1R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-en-2- yl}ferrocene (4). 4 forms orthorhombic crystals of the space group P212121 with a = 7.7163(4), b = 10.7381(6), and c = 28.804(2) A˚ , which have been subjected to X-ray diffraction.