Origin of Enantioselectivities in Chiral β-Amino Alcohol Catalyzed Asymmetric Additions of Organozinc Reagents to Benzaldehyde: PM3 Transition State Modeling

PM3 transition state (TS) models were developed for enantioselective chiral β-amino alcohol catalyzed additions of organozinc reagents to benzaldehyde. These semiempirical TS models are consistent with earlier ab initio computations on smaller model systems and with experimental data for a variety of stereoselective examples. General trends for varying chiral β-amino alcohol ligands (e.g., camphor, 1,2-diphenylethane, and proline derivatives) and alkylating agent (ZnMe 2, ZnEt 2 ) are reproduced by these models.