D A. Evans Diastereoselective Hydrogenation: Introduction Chem 206 The Hydrogenation Reaction Polar functional groups may play a role in controlling the diastereoselectivity Relevant Review articles: J M. Brown, Angew. Chem. Int. Edit. 26, 190-203 (1987) however the control elements were not well-defined ■ Genera| Mechanism H2, Pd-C howeve Historically, primary stereochemical control designed around analysis of steric environment in vicinity of C=C However, the influence of polar effects was documented J. E. McMurry& Co-workers, Tetrahedron Lett. 3731 (1970) EtOH 10% Pd-c Pd EtOH Directed OMe Thompson, J.Org. Chem. 36, 2577(1971) 5:95 Y. Kishi& Co-workers, J. Am. Chem. Soc. 102, 7156 (1980)OMe O O CO2Et CH2OH O O OMe LiAlH4 C C H R H R C C H R H R H H EtOH H2 Pd-C EtOH H2 Pd-C C C H R H R M C C H R H R H M H CO2Et O O OMe H H OMe O O CH2OH C C H R H R C C H R H R M M H H H H N O HO H H H OH CH3 CHMe2 CHMe2 O CH3 H2 H2 H H N OH HO H H H H HO N OH H H CHMe2 H OH CH3 O CH3 CHMe2 Historically, primary stereochemical control designed around analysis of steric environment in vicinity of C=C. However, the influence of polar effects was documented only isomer H2 , Pd-C however trans:cis = 55:45 H2 , Pd-C J. E. McMurry & Co-workers, Tetrahedron Lett.. 3731 (1970) D. A. Evans Diastereoselective Hydrogenation: Introduction Chem 206 The Hydrogenation Reaction Relevant Review articles: J. M. Brown, Angew. Chem. Int. Edit. 26, 190-203 (1987). trans : cis Thompson, J.Org. Chem. 36, 2577 (1971) 5 : 95 trans : cis 85 : 15 Y. Kishi & Co-workers, J. Am. Chem. Soc. 102, 7156 (1980) 10% Pd-C 5% Pd-Al2O3 sole product 12 : 1 Steric Control Directed ? Polar functional groups may play a role in controlling the diastereoselectivity of the hydrogenation process; however, the control elements were not well-defined. + ■ General Mechanism M(0) M(0) + Pd(0) Pd(II)