Addition of crotyltitanocenes to aldehydes: Influence of cyclopentadienyl substituents on the diastereoselective formation of homoallylic alcohols

Article abstract of DOI:10.1021/om00101a007

The addition of (η³-crotyl)titanocenes (2, R = H, Me, i-Pr) to primary, secondary, and tertiary aldehydes has been investigated. The products of this reaction, homoallylic alcohols, are formed with good to excellent selectivity favoring the anti diastereomer in all cases. The degree of diastereoselectivity correlates with the size of the substituent on the cyclopentadienyl ring and that on the aldehyde. For aliphatic and aromatic aldehydes an increase in diastereoselectivity with increasing steric hindrance at the metal center was observed. The results are consistent with a chairlike transition state for product formation involving slippage of the η³-allyl ligand of the allyltitanocene to η¹ with retention of allyl geometry.