Diaza-Crown Ether-Bridged Chiral Diphosphoramidite Ligands: Synthesis and Applications in Asymmetric Catalysis

Origin of Manipulating Selectivity in Prins Cyclization by [Ga4L6]12- Supramolecular Catalysis through Host-Guest Interactions

The host effect of the supramolecular [Ga4L6]12- tetrahedral metallocage on Prins cyclization reaction of the substrate by encapsulated citronellal has been investigated by means of molecular dynamics and quantum mechanics. The encapsulation process of the substrate into the [Ga4L6]12- cavity was simulated via attach-pull-release (APR) methods. Thermodynamic calculations and classical molecular dynamics simulations assessed the substrate's microenvironment inside the cavity, guiding DFT-level modeling of the reaction. DFT calculations show diol product predominance in acidic solution but high enol selectivity inside [Ga4L6]12-, consistent with experimental findings. [Ga4L6]12- alters the selectivity of the Prins cyclization reaction by inhibiting diol formation. The activation strain model-based decomposition analysis (ASM-DA) of the barrier difference among distortion and interaction terms indicates that the more positive interaction between a host and guest in the diol transition state than enol determines the product selectivity, particularly the fewer C-H···O and O-H···O hydrogen-bonding interactions. These theoretical insights could contribute to a deeper understanding of the nature of supramolecular catalysis and to further develop new supramolecular catalysts.

Rhodium-Catalyzed Asymmetric Macrocyclization towards Crown Ethers Using Hydroamination of Bis(allenes)

Enantiomerically enriched crown ethers (CE) exhibit strong asymmetric induction in phase transfer catalysis, supramolecular catalysis and molecular recognition processes. Traditional methods have often been used to access these valuable compounds, which limit their diversity and consequently their applicability. Herein, a practical catalytic method is described for the gram scale synthesis of a class of chiral CEs (aza-crown ethers; ACEs) using Rh-catalyzed hydroamination of bis(allenes) with diamines. Using this approach, a wide range of chiral vinyl functionalized CEs with ring sizes ranging from 12 to 36 have been successfully prepared in high yields of up to 92 %, dr of up to >20 : 1 and er of up to >99 : 1. These vinyl substituted CEs allow for further diversification giving facile access to various CE derivatives as well as to their three-dimensional analogues using ring-closing metathesis. Some of these chiral CEs themselves display high potential for use in asymmetric catalysis.

2-Hydroxymethyl-18-crown-6 as an efficient organocatalyst for α-aminophosphonates synthesized under eco-friendly conditions, DFT, molecular docking and ADME/T studies

Eco-friendly and simple procedure has been developed for the synthesis of α-aminophosphonates that act as topoisomerase II α-inhibiting anticancer agent, using 2-hydroxymethyl-18-crown-6 as an unexpected homogeneous organocatalyst in multicomponents reaction of aromatic aldehyde, aniline and diethylphosphite in one pot via Kabachnik-Fields reaction. This efficient method proceeds with catalytic amount, transition metal-free, at room temperature within short reaction time, giving the α-aminophosphonates derivatives (4a-r) in high chemical yields (up to 80%). Theoretical DFT calculations of three compounds (4p, 4q and 4r) were carried out in a gas phase at CAM-B3LYP 6-31G (d,p) basis set to predict the molecular geometries and chemical reactivity descriptors. The frontier orbital energies (HOMO/LUMO) were described the charge transfer and used to predict structure-activity relationship study. Molecular electrostatic potential (MEP) has also been analyzed. Molecular docking studies are implemented to analyze the binding energy and compared with Adriamycin against 1ZXM receptor which to be considered as antitumor candidates. In silico pharmacological ADMET properties as Drug likeness and oral activity have been carried out based on Lipinski's rule of five.Communicated by Ramaswamy H. Sarma.

Highly Active Rh Catalysts with Strong π-Acceptor Phosphine-Containing Porous Organic Polymers for Alkene Hydroformylation

Phosphine-containing porous organic polymers (phosphine-POPs) are a kind of potential catalyst support for alkene hydroformylation. However, the synthesis of phosphine-POPs with strong π-acceptor is still a challenge. Herein, we report the synthesis of phosphine-POPs with different π-acceptor properties [POL-P(Pyr)₃, CPOL-BPa&PPh₃-15, and CPOL-BP&PPh₃-15] and evaluated their performances as ligands to coordinate with Rh(acac)(CO)₂ for hydroformylation of alkenes. We found that the Rh center with stronger π-acceptor phosphine-POPs showed better catalytic performance. Rh/CPOL-BPa&PPh₃-15 with strong π-acceptor bidentate phosphoramidites showed obviously higher activity and regioselectivity (TON = 7.5 × 10³, l/b = 26.1) than Rh/CPOL-BP&PPh₃-15 (TON = 5.3 × 10³, l/b = 5.0) with weaker π-acceptor bidentate phosphonites. Particularly, the TON of the hydroformylation reached 27.7 × 10³ upon using Rh/POL-P(Pyr)₃ which possessed tris(1-pyrrolyl)phosphane coordination sites. Overall, our study provides an orientation to design phosphine-POPs for hydroformylation reactions.

Recent Advances in the Enantioselective Synthesis of Chiral Amines via Transition Metal-Catalyzed Asymmetric Hydrogenation

Chiral amines are key structural motifs present in a wide variety of natural products, drugs, and other biologically active compounds. During the past decade, significant advances have been made with respect to the enantioselective synthesis of chiral amines, many of them based on catalytic asymmetric hydrogenation (AH). The present review covers the use of AH in the synthesis of chiral amines bearing a stereogenic center either in the α, β, or γ position with respect to the nitrogen atom, reported from 2010 to 2020. Therefore, we provide an overview of the recent advances in the AH of imines, enamides, enamines, allyl amines, and N-heteroaromatic compounds.

Organocatalytic Asymmetric α-Allylation and Propargylation of α-Branched Aldehydes with Alkyl Halides

Enantioselective α-allylation and -propargylation of α-branched aldehydes with alkyl halides was successfully performed using a chiral primary amino acid organocatalyst. This alkylation reaction, involving the generation of a chiral quaternary carbon stereocenter, proceeded smoothly in a mildly basic aqueous solution of potassium hydrogen carbonate to furnish α-allylated or -propargylated aldehydes in a good yield (up to 87%) and high enantioselectivity (up to 96% ee).

A medium-firm drug-candidate library of cryptand-like structures on T7 phage: design and selection of a strong binder for Hsp90

We designed and synthesized a medium-firm drug-candidate library of cryptand-like structures possessing a randomized peptide linker on the bacteriophage T7. From the macrocyclic library with a 109 diversity, we obtained a binder toward a cancer-related protein (Hsp90) with an antibody-like strong affinity (KD = 62 nM) and the binding was driven by the enthalpy. The selected supramolecular ligand inhibited Hsp90 activity by site-specific binding outside of the well-known ATP-binding pocket on the N-terminal domain (NTD).

Recent developments in asymmetric hydroformylation

This review describes the recent developments in the field of asymmetric hydroformylation. A large variety of ligands is now available, some of which are extremely effective in inducing high enantio- and regioselectivity.