enantioselective reduciton of ketones by thichlorosilane

Org. Lett., 8 (17), 3789 -3792, 2006

Enantioselective reduction of ketones has been one of central topics in asymmetric synthesis over the past two decades.¹ Although a variety of reducing reagents have been used for the purpose,² there have been few studies on the use of trichlorosilane (Cl₃SiH),³ which is an economical and easy to handle reagent.⁴⁵ Because Cl₃SiH does not have the ability to reduce ketones by itself, appropriate activators are necessary for the reduction of ketones by Cl₃SiH with high efficiency. Organic chiral activators are in particular of interest in this respect because they provide a route for asymmetric reduction of ketones. We have reported a first enantioselective reduction of ketones by Cl₃SiH using chiral N-formylpyrrolidines (1q,r) as organic activators (up to 43% ee),⁴ and recently isoquinolinyloxazoline (2) was reported to work well as a chiral activator (up to 94% ee).⁶⁷