ADDITION OF A STERICALLY HINDERED, CHIRAL CROTYL ANSA-TITANOCENE COMPLEX TO ALDEHYDES

,2-ethylenebis(3-t-butylcyclopendadaienyl)titanium dichloride ([S]-5) can be obtained in high optical purity through kinetic resolution of t he racemate (rac-5) using [S]-binaphthol. The structure of 1,2-ethylen ebis(3-t-butylcyclopentadienyl)titanium binaphtholate (rac-7) was dete rmined by X-ray crystallography: C40H40O2Ti, monoclinic, P2(1)/c, a = 14.455(3) Angstrom, b = 13.710(3) Angstrom, c = 17.278(4) Angstrom, be ta = 109.80(2)degrees, V = 3221.7(13) Angstrom, Z = 4, 4599 observed r eflections with F greater than or equal to 6 sigma(F), R = 0.0337, R(w ) = 0.0359. The addition of [S] = 1,2-ethylenebis(3-t-butylcyclopentad ienyl)titanium ([S]-6), formed in situ from [S]-5, to aldehydes was in vestigated and provides beta-methyl homoallylic alcohols in moderate y ields. The stereoselectivity of the reaction and the sense of asymmetr ic induction depends on the steric bulk of the aldehyde. The results w ere rationalized using the results of a molecular modelling study on t ransition state models which reproduced the general trends in the expe rimental results.