SYNTHESIS OF CAMPHOR-DERIVED CHIRAL CYCLOPENTADIENES VIA THE NAZAROV CYCLIZATION - PREPARATION OF CHIRAL BIS(CYCLOPENTADIENYL)ZIRCONIUM ANDBIS(CYCLOPENTADIENYL)TITANIUM DICHLORIDES

Nazarov cationic pi-cyclizations were employed in the synthesis of thr ee substituted camphor-derived cyclopentadienyl ligands bearing a 3-me thyl, 3-t-butyl or 3-phenyl substituent on the 0,10-trimethyltricyclo[ 5,2,1,0(2,6)]deca-2,5-diene framework. These ligands were converted to diastereomeric mixtures of bis(cyclopentadienyl)zirconium and -titani um dichlorides. In each case a C-2-symmetrical isomer was the major is omer in the crude reaction product mixture and in all but one case a p ure C-2-symmetrical diastereomer could be obtained by recrystallizatio n.