Rhodium-catalyzed asymmetric hydroboration using TADDOL-derived phosphites and phosphoramidites

ORGN 30

James M. Takacs, jtakacs1@unl.edu1, Shin A. Moteki, selfassemblyligand@yahoo.com2, Di Wu1, Kusumlata Chandra1, and D. Sahadeva Reddy1. (1) Department of Chemistry, Univ of Nebraska-Lincoln, Lincoln, NE 68588-0304, (2) Department of Chemistry, University of Nebraska-Lincoln, Lincoln, NE 68588-0304
The rhodium-catalyzed hydroboration has attracted significant interest, in part, due to the conceptual novelty of catalyzing an otherwise common transformation and the observation that it proceeds with complementary regio- and/or diastereoselectivity in certain substrates. For example, in contrast to the uncatalyzed reaction, the rhodium-catalyzed hydroboration of styrene affords predominantly the branched alcohol, 1-phenylethanol. The asymmetric reaction has advanced considerably since Hayashi's seminal paper in 1989 and the range of chiral ligands that can be used to effect enantioselective hydroboration has increased substantially; however, even within a group of closely related vinyl substrates, the level of asymmetric induction often varies widely. We screened a series of chiral phosphites and phosphoramidites in a multi-substrate reaction and uncovered several ligands that afford 90-97% ee with a series of substituted styrenes bearing substituents ranging from strongly electron donating to electron withdrawing.

 

Asymmetric Reactions and Syntheses
8:00 AM-11:40 AM, Sunday, 26 March 2006 Georgia World Congress Center -- C302, Oral

Division of Organic Chemistry

The 231st ACS National Meeting, Atlanta, GA, March 26-30, 2006