A Systematic Study of Functionalized Oxiranes as Initiating Groups for Cationic Polycyclization Reactions

Three different methods have been developed that effectively utilize chiral oxiranes derived from Katsuki–Sharpless epoxidation of allylic alcohols as initiating groups for cationic cyclization of unsaturated substrates to form chiral polycycles. This type of transformation has previously been problematic. These employ either epoxy-methoximes, vinyl-substituted oxiranes, or hydroxymethyl oxiranes. All three approaches are described in detail. In addition, this research has led to possible explanations for previously encountered difficulties in this area and provided two new insights into the Lewis acid activation of oxiranes. The methodology described herein constitutes a valuable link between two powerful synthetic constructions, enantioselective Katsuki–Sharpless epoxidation and cationic polycyclization reactions

A Systematic Study of Functionalized Oxiranes as Initiating Groups for Cationic Polycyclization Reactions

Three different methods have been developed that effectively utilize chiral oxiranes derived from Katsuki–Sharpless epoxidation of allylic alcohols as initiating groups for cationic cyclization of unsaturated substrates to form chiral polycycles. This type of transformation has previously been problematic. These employ either epoxy-methoximes, vinyl-substituted oxiranes, or hydroxymethyl oxiranes. All three approaches are described in detail. In addition, this research has led to possible explanations for previously encountered difficulties in this area and provided two new insights into the Lewis acid activation of oxiranes. The methodology described herein constitutes a valuable link between two powerful synthetic constructions, enantioselective Katsuki–Sharpless epoxidation and cationic polycyclization reactions

Carbon Bond Catalysis: Dialkyl Sulfates, Alkyl Sulfonates and Alkyl Hal-ides as Catalysts in Acetal Forming and Related Reactions

This study demonstrates a previously unexplored facet of sp3-carbon electrophiles (or alkylating agents): their potential for catalytic applications through carbon-bond interactions. In contrast to their classical SN1 and SN2 reactions, we present an al-ternate perspective, the catalytic nature of alkyl electrophiles through noncovalent interactions (NCIs). The involvement of NCIs by carbon electrophiles (possessing polar Csp3-X bonds) in stabilizing conformations of small molecules and biomole-cules has recently been discovered. Nevertheless, their catalytic role in activating small molecules has not been observed. As the "X" group evolves into an effective leaving group, carbon electrophiles develop strong positive potentials on the carbon surface (σ-hole). However, small atomic size and steric congestion resulting from the presence of four groups around the carbon atom pose challenges in establishing strong σ-hole interactions with nucleophilic acceptors. This unique behavior of alkyl electrophiles has deterred chemists from exploring their potential as catalysts in chemical transformations. In groundbreaking revelation, we demonstrate for the first time that alkyl electrophiles function as Lewis acid catalysts in activating carbonyls for acetal formation and related reactions through NCIs. We meticulously chose a range of alkyl electrophiles and discovered a striking correlation between their molecular electrostatic potential (MEP) surface energies and their catalytic efficacy in acetal-forming reactions. Our comprehensive approach, which encompassed both experimental and theoretical investigations, provided robust support for the catalytic potential of alkyl electrophiles through non-covalent carbon bond interactions

Short Route to Platencin

The synthesis of the complex tricyclic core of the terpenoid antibiotic platencin is achieved in a concise, protecting group-free and stereoselective manner. A flexible approach that highlights the intramolecular aldol reaction as the key step toward the construction of the bicyclo[2,2,2]octane ring from an angular allyl decalone in both the <i>trans</i>-fused and the <i>cis</i>-fused forms is demonstrated

A New, Short, and Stereocontrolled Synthesis of <i>C</i>₂‑Symmetric 1,2-Diamines

The previously unknown 5-spirocyclohexylisoimidazole has been made efficiently and simply by reaction of ammonia, glyoxal hydrate, and cyclohexanone. It is a very useful precursor for the diastereocontrolled synthesis of many <i>C</i>₂-symmetric 1,2-diamines, a class which is important for the generation of a variety of <i>C</i>₂-symmetric reagents and catalysts for enantioselective synthesis

Experimental realization of multipartite entanglement via quantum Fisher information in a uniform antiferromagnetic quantum spin chain

Quantum entanglement is a quantum-mechanical phenomenon where the quantum state of a many-body system with many degrees of freedom cannot be described independently of the state of each body with a given degree of freedom, no matter how far apart in space each body is. Entanglement is not only considered a resource in quantum information but is also believed to affect complex condensed-matter systems. Detecting and quantifying multiparticle entanglement in a many-body system is thus of fundamental significance for both quantum information science and condensed-matter physics. Here, we detect and quantify multipartite entanglement in a spin-1/2 Heisenberg antiferromagnetic chain in a bulk solid. Multipartite entanglement was detected by using quantum Fisher information which was obtained using dynamic susceptibility measured via inelastic neutron scattering. The scaling behavior of quantum Fisher information was found to identify the spin-1/2 Heisenberg antiferromagnetic chain to belong to a class of strongly entangled quantum phase transitions with divergent multipartite entanglement