In Situ–Generated Zinc Bromide–Catalyzed α‐Bromination of Alkanones in Water

α‐Bromination of alkanones with bromine catalyzed by in situ–generated zinc bromide from zinc dust and bromine in water is investigated. Bromination with dioxane‐dibromide as a source of bromine does not require zinc dust and provides selectively α‐mono and α,α‐dibromo products in excellent yields when water is used as solvent.     

Enantioselective Catalytic Addition of N-Acyl Radicals: In Batch and In Flow Organophotoredox α-Amination of Aldehydes

The organophotoredox catalytic enantioselective addition of N-acyl radicals to aldehydes, to afford enantioenriched N-acyl 1,2 aminoalcohols was studied. Under the best conditions, in batch, the product was isolated in up to 52 % yield and 85 % e.e., using a low cost and commercially available chiral imidazolidinone as organocatalyst. The reaction was then studied in flow, exploring different experimental setups and photoreactors. Although modest yields were obtained, the in-flow process afforded the product in higher productivities (up to 60 times higher) and improved space time yields (increased up to 113 times) compared to the batch reaction, with no loss of stereoselectivity.     

Enantioselective Addition of Phenylacetylene to Aldehydes Catalyzed by Polymer-Supported Sulfonamide

Enantioselective formation of C-C bonds is an area of intense research. Among them, the asymmetric addition of alkynyl reagents to aldehydes is very useful for the synthesis of chiral secondary propargyl alcohols.[1] Recently, many significant homogeneous chiral ligands have been disclosed,[2,3] but very few efficient heterogeneous catalysts have been reported. Herein, we report our research results in the asymmetric addition of phenylacetylene to aldehydes catalyzed by polymer-supported chiral sulfonamide.     

Condensation of α-Cyanothioacetamide with Aldehydes Catalyzed by Envirocat EPZG1

Condensation of α-cyanothioacetamide with aldehydes has been carried out in excellent yield under mild conditions by using Envirocat EPZG as a heterogenous reusable catalyst.     

Enantioselective Addition of Diethylzinc to Aldehydes Catalyzed by N-Sulfonylated Amino Alcohols

Asymmetric C-C bond forming reactions are of prime importance in modem synthetic organic chemistry. The use of chiral amino alcohol ligands is widespread in this area.[1] Herein, we describe the synthesis of N-sulfonylated amino alcohols 1～4 and enantioselective addition of diethylzinc to aldehydes was carried out employing titanium(Ⅳ) complexes 1～4.     

Asymmetric Addition of Diethylzinc to Aldehydes Catalyzed by Chiral γ_Amino Alcohols

Although the asymmetric additions of diethylzinc to aldehydes have been extensively studied in the presence of chiral catalyst, most of the chiral ligands tested are b-amino alcohols1. In this report, the synthesis of chiral gamino alcohols 1-4 from the reaction of (+)-camphor and (-)-menthone with 2-lithiomethyl-6-methyl-pyridine or 2-picolly- lithium2, which give a single diasteromer as determined by 1H NMR with high yields (Scheme 1)3, and their application in the enantioselective additio…     

Polystyrene-Supported Aminocatalyst Derived from Diarylprolinol for Asymmetric α-Amination of Aldehydes

A new class of polystyrene-supported aminocatalysts with a triazole linker from diphenyl prolinol were developed. Their catalytic activity was tested in the asymmetric α-amination of aldehydes. The substrate scope of this catalysis was studied under the optimized reaction conditions. The reusability of the polystyrene-supported aminocatalyst was demonstrated up to four cycles. Based on the reaction results, a reaction mechanism was proposed for the asymmetric α-amination of aldehydes.     

Catalytic Asymmetric Friedel–Crafts Alkylation of Indole via In Situ Generated Indol-2-one

An asymmetric Friedel–Crafts alkylation of indole with in situ generated indol-2-one from functionalized 3-bromooxinidole catalyzed by chiral N,N’-dioxide/Ni(BF₄)₂ has been developed. This protocol provides an efficient route to stereoselective construction of a series of 3-substituted 3’-indolyloxindoles bearing a quaternary carbon center in excellent yields and enantioselectivities (up to 99 % ee). In addition, the conversion of the resulted 3-substituted 3’-indolyloxindole to the key intermediate for the formal synthesis of (+)-folicanthine was also demonstrated.     

Selective Hydrogenation of α,β-Unsaturated Aldehydes Catalyzed by Amine-Capped Platinum-Cobalt Nanocrystals

More Greasy, More Selective: Amine-capped Pt(3) Co nanocatalysts were synthesized and used for the hydrogenation of cinnamaldehyde (CAL). Capping the catalysts with amines that contain long carbon chains results in an ordered surface "array", in which high selectivity towards C?O hydrogenation can be achieved because the C?C bond in CAL does not interact with the surface. The longer the carbon chains in the amine, the higher the selectivity.     

Pd-Catalyzed Cross-Coupling of Acyl Chlorides with In Situ–Generated Alkynylzinc Derivatives for the Synthesis of Ynones

A mild and operationally simple procedure by Pd-catalyzed cross-coupling of acyl chlorides with in situ–generated alkynylzinc derivatives was developed, giving the corresponding ynones in good yields.

Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® full experimental and spectral details.     

Asymmetric Reformatsky Reaction of Aldehydes Catalyzed by Novel β-Amino Alcohols and Zinc Complexes

A series of β-amino alcohols derived from (1R, 2S)-2-amino-1,2-diphenylethanol and substituted salicylaldehydes as novel chiral tridentate ligands has been applied to an asymmetric Reformatsky reaction of aldehydes with ethyl iodoacetate in the presence of ZnMe₂. This novel catalytic system produced the desired β-hydroxyl esters with moderate to good enantioselectivities (up to 81% ee) and yields for many aldehydes, including aromatic, heteroaromatic, conjugated, and aliphatic aldehydes.     

Research on the Cyanosilylation of Prochiral Aldehydes Catalyzed by Alkyldimethoxyl Silylene–Bridged Lanthanide Complexes

A series of novel silylene‐bridged Ln‐O rare earth complexes are very efficient Lewis acidic catalysts in cyanosilylation of aldehydes, giving some cyano trimethylsilyl ethers of aldehydes in >99% yields.     

CuI-Catalyzed,One-Pot,Three-Component Huisgen Cycloaddition Reaction of Conjugated Enynes and In Situ–Generated Azides

A novel and efficient copper(I)-catalyzed three-component Huisgen cycloaddition reaction of conjugated enynes, alkyl halides, and sodium azide has been developed. These reactions were performed in the absence of amide ligands at room temperature, and the corresponding mono- and bis-1,2,3-triazoles were obtained in good to excellent yields in a one-pot procedure.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Enantioselective Addition of Diethylzinc to Aromatic Aldehydes Catalyzed by Pyrolidine and Piperidine β-Amino Alcohols

The enantioselective alkylation of aryl aldehydes by diethylzinc in the presence of catalytic amounts of several chiral pyrolidine- and piperidine-based amino alcohol ligands, synthesized from the reaction of (R)-2-amino-1-butanol and (S)-2-amino-3-phenylpropan-1-ol with appropriate dibromoalkanes, was studied. The influence of temperature and ligand structure has been investigated. Addition of diethylzinc to aromatic aldehydes under the optimized condition gave the corresponding products in excellent yields with ee values of up to 77%.     

Synthesis of d,l-α-Tocopherol Catalyzed by Heteropoly Acids

d,l-a-Tocopherol(vitaminE)isgenerallysynthesizedbycondensingtrimethylhydroquinone(TMHQ)withphytolorisophytolcatatyzedbyvariousBronstedandLex'llisacidssuchasZnCI,-HCI'andAICI;'.Anessentialdisadvantageofthesecatalystsistheirhighconsumption.TheratioofZnCI,toTMHQIsaboLltI(I.Futhertllore.thecatalystsaredifficulttoberecoveredandreused.Recentl}.I.V.Rozhevnikovandco-workers'reportedthatthereactioncouldbecatalyzedbyheteropolyacids(HPA)H:PW,=O.,andH;SiW,=O..,.TheconsumptionoftheseHPAw…     

Zirconocene Dichloride–Catalyzed Pinacol Coupling of Aromatic Aldehydes and Ketones

The reductive coupling of aromatic aldehydes and ketones has been achieved using a catalytic amount of zirconocene dichloride in the presence of magnesium metal and chlorotrimethylsilane in THF at room temperature to afford the corresponding 1,2‐diols in good yields and diastereoselectivity.     

Aldol Condensation of β-Diketones and β-Ketoesters with Aldehydes Catalyzed by Samarium (III) Iodide

Catalyzed by SmI₃ β-diketones and β-ketoesters condense with aldehydes to give benzylidene substituted β-diketones and β-ketoesters at room temperatures in fair yields.     

p-Toluene Sulfonic Acid–Catalyzed,Solvent-Free Synthesis of Symmetrical Bisamides by Reaction Between Aldehydes and Amides

Reaction between aldehydes and amides catalyzed by p-toluene sulfonic acid in solvent-free conditions provided a simple and efficient one-pot route for the synthesis of symmetrical bisamide derivatives in excellent yields.     

Molecular-Sieving Membrane by Partitioning the Channels in Ultrafiltration Membrane by In Situ Polymerization

Commercial ultrafiltration membranes have proliferated globally for water treatment. However, their pore sizes are too large to sieve gases. Conjugated microporous polymers (CMPs) feature well-developed microporosity yet are difficult to be fabricated into membranes. Herein, we report a strategy to prepare molecular-sieving membranes by partitioning the mesoscopic channels in water ultrafiltration membrane (PSU) into ultra-micropores by space-confined polymerization of multi-functionalized rigid building units. Nine CMP@PSU membranes were obtained, and their separation performance for H₂/CO₂, H₂/N₂, and H₂/CH₄ pairs surpass the Robeson upper bound and rival against the best of those reported membranes. Furthermore, highly crosslinked skeletons inside the channels result in the structural robustness and transfer into the excellent aging resistance of the CMP@PSU. This strategy may shed light on the design and fabrication of high-performance polymeric gas separation membranes.     

In Situ Construction of Pt–Ni NF@Ni-MOF-74 for Selective Hydrogenation of p-Nitrostyrene by Ammonia Borane

Pt–Ni nanoframes (Pt–Ni NFs) exhibit outstanding catalytic properties for several reactions owing to the large numbers of exposed surface active sites, but its stability and selectivity need to be improved. Herein, an in situ method for construction of a core–shell structured Pt-Ni NF@Ni-MOF-74 is reported using Pt–Ni rhombic dodecahedral as self-sacrificial template. The obtained sample exhibits not only 100 % conversion for the selective hydrogenation of p-nitrostyrene to p-aminostyrene conducted at room temperature, but also good selectivity (92 %) and high stability (no activity loss after fifteen runs) during the reaction. This is attributed to the Ni-MOF-74 shell in situ formed in the preparation process, which can stabilize the evolved Pt–Ni NF and donate electrons to the Pt metals that facilitate the preferential adsorption of electrophilic NO₂ group. This study opens up new vistas for the design of highly active, selective, and stable noble-metal-containing materials for selective hydrogenation reactions.