Theoretical and experimental studies of asymmetric organozinc additions to benzaldehyde catalyzed by flexible and constrained gamma-amino alcohols.
The cis-decalin based gamma-amino alcohols, 1-5, were synthesized, resolved, and employed as catalysts in the addition of organozincs to benzaldehyde. Despite large facial differentiation in the RZn adducts of the ligands, the enantioselectivities were found to be moderate. Transition structure calculations were done using several quantum chemical methods to examine the underlying causes of the selectivity for three gamma-amino alcohols, 1, 2, and 3. The tricyclic mu-oxo (6/4/4), rather than the bicyclic six-membered (6/6), transition structures were found to explain the observed enantioselectivity for 2 and 3. MP2 calculations gave the best correlation to the experimental results compared to B3LYP and HF calculations. The conformational flexibility of the chiral ligands was found to be an important factor in the selectivity.
Panda
Manoranjan
M
Department of Chemistry, Roy and Diana Vagelos Laboratories, University of Pennsylvania, Philadelphia 19104, USA.
Phuan
Puay-Wah
PW
Kozlowski
Marisa C
MC
D000605:Amino Alcohols / Q000138:chemical synthesis* / Q000737:chemistry; D001547:Benzaldehydes / Q000138:chemical synthesis* / Q000737:chemistry; D002384:Catalysis; D002625:Chemistry, Organic / Q000379:methods; D008024:Ligands; D008962:Models, Theoretical; D008968:Molecular Conformation; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D013237:Stereoisomerism; D015032:Zinc / Q000737:chemistry*
D000605:Amino Alcohols; D001547:Benzaldehydes; D008024:Ligands; D009942:Organometallic Compounds; D015032:Zinc