Chiral ytterbium complex-catalyzed direct asymmetric aldol-Tishchenko reaction: synthesis of anti-1,3-diols

The asymmetric aldol-Tishchenko reaction of aromatic aldehydes with aliphatic and aromatic ketones has been developed as an efficient strategy for the synthesis of anti-1,3-diols in good yield with high diastereocontrol and good levels of enantioselectivity. This domino-type reaction is catalyzed by a chiral ytterbium complex that promotes both the aldol reaction through enolization of the carbonyl compound and the Evans-Tishchenko reduction of the aldol intermediate. The stereochemistry of the resulting diols is also investigated and finally proved by using CD techniques.     

The first example of a catalytic asymmetric aldol-Tishchenko reaction of aldehydes and aliphatic ketones

A number of combinations of Lewis acids and chiral ligands has been screened for the enantioselective direct tandem aldol condensation--Evans-Tishchenko reduction of aldehydes and ketones. Chiral ytterbium complexes were found to catalyze the condensation of aromatic aldehydes with 3-pentanone (and other ketones) giving rise to the anti-1,3-diol monoesters in good yield, and with high diastereocontrol and moderate levels of enantioselectivity. Three adjacent stereogenic centers are created in one reaction sequence in acyclic systems.     

手性助剂诱导催化不对称Strecker反应研究进展

亚胺的不对称Strecker反应是合成α-氨基酸化合物的重要途径之一,一般在手性助剂的诱导下进行.近年来,用于诱导不对称Strecker反应的各类手性助剂的研究受到广泛关注.本文综述了α-苯乙胺、α-氨基酸、α-氨基酸衍生的酰胺、α-苯甘氨醇、亚磺酰基亚胺、糖胺、肼等七类化合物作为手性助剂在不对称Strecker反应中的应用研究现状,就该研究领域存在的问题进行了分析,并对其前景进行了展望.     

Catalytic, asymmetric aza-Baylis-Hillman reaction of N-sulfonated imines with activated olefins by quinidine-derived chiral amines

The chiral nitrogen Lewis base, tricyclic cinchona alkaloid derivative TQO, is an effective promoter in the catalytic, asymmetric aza‐Baylis–Hillman reaction of N‐sulfonated imines Ar? CH?NR′ 1 (R′ = Ts, Ms, Ns, SES) with various activated olefins such as methyl vinyl ketone (MVK), ethyl vinyl ketone (EVK), acrolein, methyl acrylate, phenyl acrylate, or α‐naphthyl acrylate to give the corresponding adducts in moderate to good yields with good to high ee (up to 99 %) at ?30 °C or 45 °C in various solvents, including DMF/MeCN (1:1, v/v). The first such reaction of 1 with the simplest Michael acceptor MVK and methyl acrylate has been achieved with excellent enantioselectivity. The adducts derived from MVK and EVK had the opposite absolute configuration to those from acrolein, methyl acrylate, phenyl acrylate, and α‐naphthyl acrylate. A plausible mechanism has been proposed on the basis of previous reports and the authors’ investigations. An effective bifunctional chiral nitrogen Lewis base–Brønsted acid system has been revealed in this type of aza‐Baylis–Hillman reaction.     

Catalytic asymmetric synthesis of spirooxindoles by a mannich-type reaction of isothiocyanato oxindoles

Easy access: a strontium/Schiff base complex as catalyst for the title reaction provided straightforward access to enantiomerically enriched spiro[imidazolidine-4,3'-oxindole] compounds, as well as a spiro[imidazoline-4,3'-oxindole] through a two-step conversion from the Mannich adduct.     

A simplified catalytic system for direct catalytic asymmetric aldol reaction of thioamides; application to an enantioselective synthesis of atorvastatin

A new catalytic system was developed for the direct catalytic asymmetric aldol reaction of thioamides. The new lithium-free Cu catalyst (second-generation catalyst) exhibited enhanced catalytic efficiency over the previously developed catalyst comprising [Cu(CH₃CN)₄]PF₆/Ph-BPE/LiOAr (first-generation catalyst), which required a tedious catalyst preparation process. In the reaction with the second-generation catalyst, the intermediate Cu-aldolate functioned as a Brønsted base to generate thioamide enolate, efficiently driving the catalytic cycle. The present aldol methodology culminated in a concise asymmetric synthesis of atorvastatin (Lipitor^®: atorvastatin calcium), a widely prescribed HMG-CoA reductase inhibitor for lowering low-density lipoprotein cholesterol.