Direct Stereoselective Synthesis of a Single (ebthi)Ti(BINOLate) Catalyst Enantiomer

Despite their prominence as privileged chiral catalysts
for synthesis
and polymer chemistry, the synthesis of enantiopure ebthi-type titanocenes
is a challenging task. In this proof-of-concept study, we report the
development of a single-step synthesis of (S,S,S)-(ebthi)Ti(BINOLate) from Li2(ebthi) and (S)-Ti(BINOLate)Cl2 in 28%
yield with 97% ee. We further shed light on the nature of the latter
and provide alternative protocols for the convenient liberation of
(S)-(ebthi)TiCl2. (ebthi)-Ti(BINOLate)
is further shown to be a competent catalyst in asymmetric ketone-nitrile
couplings, providing an enantioselectivity comparable to that of (ebthi)TiCl2.