ENANTIOSELECTIVE REDUCTION OF BENZOYL DERIVATIVES OF FERROCENE AND RUTHENOCENE - OPTICALLY-ACTIVE CARBINOLS AND CARBENIUM IONS

Mono- and 1,1'-disubstituted metallocenes, XC5H4MC5H4Y, M = Fe, Ru, X = H, Y = COPh, or X = Y = COPh, have been reduced using the LiAlH4-Chirald complex to afford the corresponding carbinols and diols enantiomerically enriched. Optical yield was 53% for benzoylferrocene and 86% for benzoylruthenocene, (R)-configuration being predominant. Monocations had an opposite sign of rotation and were stable in CF3COOH. On the contrary, diols have lost optical rotation in the same acid that has been explained by formation of the achiral ether intermediate. Dication has been formed in DSO3F as evidenced by the H-1 NMR spectrum but it is completely racemized even at low temperature.