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Despite the significance of chiral allene skeletons in catalysis, organic synthesis and medicinal chemistry et al. there is a scarcity of reports on axially chiral allenyl phosphorus compounds. Here, we disclosed an efficient and straightforward cascade reaction between ethynyl ketones and phosphine oxides, resulting in a broad array of trisubstituted allenes incorporating a phosphorus moiety in high yields with excellent stereoselectivities facilitated by peptide‐mimic phosphonium salt (PPS) catalysis, Additionally, comprehensive series of mechanistic experiments have been conducted to elucidate that this cascade reaction proceeds via an asymmetric Pudovik addition reaction followed by a subsequent phospha‐Brook rearrangement that occurs concomitantly with kinetic resolution, representing a stereospecific rearrangement and protonation process facilitating central‐to‐axial chirality transfer in a cascade manner. We anticipate that our research will pave the way for a promising exploration of novel stereo‐induction pattern in the Pudovik addition/phospha‐Brook rearrangement cascade reaction. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations at the M062X-D3/def2-TZVP//M062X-D3/def2-SVP level of theory were employed to reveal the mechanism of the reaction between CO2 and styrene oxide for cyclic carbonate, mediated by guanidine and tetrabutylammonium iodide (TBAI) co-catalysts. The noncatalytic reaction occurred via a concerted mechanism, with energy barriers as high as 64.1 and 78.0 kcal mol−1. Three elementary steps were included in the catalytic reaction, and epoxide ring-opening by nucleophilic attack of an iodide anion was predicted to be the rate-determining step (RDS). Guanidine acted as the H-bond donor to activate styrene oxide by (N)H⋯O interaction, facilitating epoxide ring-opening with a low activation barrier (ΔG≠ = 22.2–29.6 kcal mol−1). A good linear correlation between the acidity of the NH group in the guanidine and the energy barrier in the epoxide ring-opening step was observed. The introduction of an amide group could strengthen the hydrogen bonding ability of the guanidine catalyst toward a styrene oxide substrate, decreasing the activation barrier for the cyclic carbonate product. When the guanidine–Cu(I) complex was used as the Lewis acid catalyst, the styrene oxide was activated by O⋯Cu(I) coordination in organometallic catalysis. The energy barriers in the presence of guanidine–Cu(I)/TBAI catalysts could be decreased in contrast to the non-catalytic reaction. [ABSTRACT FROM AUTHOR]

The precise and efficient construction of axially chiral scaffolds, particularly toward the aryl-alkene atropoisomers with impeccably full enantiocontrol and highly structural diversity, remains greatly challenging. Herein, we disclose an organocatalytic asymmetric nucleophilic aromatic substitution (SNAr) reaction of aldehyde-substituted styrenes involving a dynamic kinetic resolution process via a hemiacetal intermediate, offering a novel and facile way to significant axial styrene scaffolds. Upon treatment of the aldehyde-containing styrenes bearing (o-hydroxyl)aryl unit with commonly available fluoroarenes in the presence of chiral peptide-phosphonium salts, the SNAr reaction via an exquisite bridged biaryl lactol intermediate undergoes smoothly to furnish a series of axially chiral aldehyde-containing styrenes decorated with various functionalities and bioactive fragments in high stereoselectivities (up to >99% ee) and complete E/Z selectivities. These resulting structural motifs are important building blocks for the preparation of diverse functionalized axial styrenes, which have great potential as efficient and privileged chiral ligands/catalysts in asymmetric synthesis. The precise and efficient construction of axially chiral scaffolds, particularly toward the aryl-alkene atropoisomers remains challenging. Here, the authors discuss an organocatalytic asymmetric nucleophilic aromatic substitution reaction of aldehyde-substituted styrenes involving a dynamic kinetic resolution process via a hemiacetal intermediate, offering a pathway to axial styrene scaffolds. [ABSTRACT FROM AUTHOR]

The solvent effect has been widely explored in small molecule reactions. However, understanding of the solvent effect on the degradation of thermosetting polymers, especially when it comes to mixed solvents, remains largely elusive. Here the effect of mixed solvents on the oxidative degradation of typical epoxy thermosets is presented. An enhancement effect of the swelling and diffusion was observed in mixed solvents of water and organic solvents, with a higher interaction energy. Besides, the introduction of an organic solvent can enhance the oxidation activities of an oxidant cerium ammonium nitrate aqueous solution. The multiple effects greatly promote the degradation of epoxy thermosets and complete degradation was even achieved at room temperature. This unconventional result reveals the synergistic effects of mixed solvents in polymer degradation and opens a new insight on polymer recycling. It is expected to guide polymers to achieve high value-added recovery and conversion with low energy consumption. [ABSTRACT FROM AUTHOR]