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Asymmetric Silylcyanation And Asymmetric Baylis-Hillman Reaction Of Aldehydes

Posted on:2005-07-09Degree:DoctorType:Dissertation
Country:ChinaCandidate:K HeFull Text:PDF
GTID:1101360182961584Subject:Organic Chemistry
Abstract/Summary:PDF Full Text Request
In the research of asymmetric silylcyanation, a novel class of chiral cyclophosphonodiamides (+)-c and (+)-d containing a free phenolic hydroxyl group were designed and synthesized starting from D-camphor. Three crystals of the optically active cyclic phosphorodiamidates and phosphonodiamide were prepared by recrystallization. The absolute configurations of these compounds were determined via X-ray diffraction analyses. The catalytic activity of the chiral phosphorus compounds in the asymmetric silylcyanation of aromatic aldehydes was investigated. The influence of different factors, such as amount of catalyst, reaction temperature, substrate and structure of catalyst, on the enantioselectivity of the reaction was also discussed. It was found that this type of chiral phosphorus reagent has good catalytic activity for the asymmetric silylcyanation reaction. When o-methoxybenzaldehyde was used as substrate, excellent enantioselectivity (98.3%) was observed in the presence of (+)-d as ligand catalyst. The P-O to P-C rearrangement upon treatment of cyclophosphorodiamidates with n-BuLi was studied. Crystallographic study revealed that this rearrangement reaction proceeded with total retention of configuration at the phosphorus atom. For the asymmetric Baylis-Hillman reaction, five chiral activated alkened were synthesized starting form readily available chiral sources and their asymmetric induction ability in the asymmetric Baylis-Hillman reaction were examined. In Me3N.H2O/solvent system, (-)-menthyl acrylate and N-α-phenylethyl acrylamide were found to be highly effective to the diastereoselective Baylis-Hillman reaction. The corresponding chiral adducts were obtained with high diastereomeric excesses (up to 98.4% and 97.4% de, respectively). Enantiomerically enriched adducts were formed in the asymmetric Bayli-Hillman reaction employing (salen)Co(II) combined with tertiary amines as catalysts.
Keywords/Search Tags:asymmetric silylcyanation, chiral phosphorus compounds, asymmetric Baylis-Hillman reaction, asymmetric synthesis
PDF Full Text Request
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