Organic chemistry frontiers : an international journal of organic chemistry最新文献

To utilize [n]helicene-embedded polycyclic aromatic hydrocarbons in the development of circularly polarized materials high luminescence quantum yield and dissymmetric factors are essential to boost (chir)optical properties. Previously we have shown that the (chir)optical properties of pyrene fused mono helicenes can be significantly influenced by the fusing mode and molecular symmetry. We report in this manuscript the stereospecific synthesis and (chir)optical properties of C₁ symmetric pyrene fused double [7]helicene, where the helicene units are connected via hexagonal and heptagonal rings. In line with single helicene congeners, lower symmetric heptagon containing double helicene exhibited higher absorption and emission dissymmetric factors along with a significant increase in fluorescence quantum yield. Our findings in this manuscript provide further insights into the effect of molecular symmetry on the (chir)optical properties of single and double helicenes.

The hybridization state of carbon atoms between phenylene units in p-cyclophanes is shown to control the guest binding properties of these hosts. Dimeric cyclophanes can be shape-switched by redox so that small aromatics can be captured or released. Trimeric cyclophanes perform similar functions on polypyridineRu(ii) complexes. Controlled capture and release are key to delivery of such cargos. The luminescence and electrochemical signals which are modulated during these processes serve as sensing functions. Some of these modulations are so strong that Boolean logic schemes can be applied. Small-scale serial integration of sequential and combinational logic is seen.

Nitrogen- and sulfur-containing heterocyclic compounds widely exist in bioactive natural products and drug molecules with unique bioactivity. In the past few decades, great efforts have been devoted to developing convenient and efficient strategies for the synthesis of these compounds. Pyridinium zwitterions with unique reactivity play a significant role in the construction of nitrogen- and sulfur-containing heterocycles. In recent years, pyridinium zwitterions have been extensively used in cyclization reactions for the synthesis of novel heterocyclic compounds. This review summarizes the recent advances in cyclization reactions involving pyridinium 1,n-zwitterions (n = 4 and 5) and highlights the applications of these zwitterions in the efficient construction of heterocycles.

Divergent oxidative Heck reaction has proven to be reliable for the rapid construction of molecular complexity, while olefins switched the outcome that remained underexplored. Herein, olefins tuned the divergent oxidative Heck reaction with O₂, enabled by self-assembled imines, which was achieved with site selectivity and stereoselectivity. The compatiblity of strongly coordinating pyridines and quinolines enabled the concise delivery of a selective serotonin 4 receptor ligand, topotecan, and irinotecan analogues.

C–C bond reduction and reorganization are fundamentally important in organic synthesis. However, there are no practical methods for tandem C–C reduction and reorganization. Here we report a versatile approach for selective reduction of the unstrained C(sp³)–C(sp³) bond of ketones, including hydrogenolytic [2 + 2 + 2]-cycloreversion of 2,4-diaroylcyclohexanols, without requiring protecting groups or hydrogen gas. Mechanistic data demonstrate that the C–C cleavage occurs via a bimetallic pathway, and nucleophile trapping of the resulting enone is crucial for C–C reduction relay. Moreover, a practical strategy for intramolecular C–C cascade reorganization is established via iterative retro-Michael/intramolecular Michael addition sequence, thus enabling cyclizative degradation of poly(vinylketone) to trisubstituted cyclohexanes. These results could open new prospects for unstrained C(sp³)–C(sp³) bond disconnection and reconstruction.

Artemeriopolides A–D (1–4), four novel cadinane sesquiterpenoid dimers featuring the rare 2-oxaspiro[4.6]undecan-1,7-dione, 2-oxaspiro[4.5]decan-1-one, and 2-oxaspiro[5.5]undecan-1-one ring systems, were isolated from Artemisia eriopoda. They are classified as two types of carbon skeletons and the structures and absolute configurations were elucidated by extensive spectral data, ECD calculations, and X-ray crystallography analyses. Antihepatoma cytotoxicity was assayed for compounds 1–4, which suggested that compound 1 was the most active against HepG2, Huh7, and SK-Hep-1 cells with IC₅₀ values of 33.6, 59.9, and 56.9 μM, respectively. The Transwell assay indicated that artemeriopolide A (1) inhibited cell migration and invasion in HepG2 cells with migration ratios of 89.9%, 62.4%, and 62.2% and invasion ratios of 46.8%, 43.6%, and 15.7% at the concentrations of 16.8, 33.6, and 67.2 μM, respectively. Western blot assay demonstrated that artemeriopolide A (1) downregulated the expression of vimentin and N-cadherin and upregulated the expression of E-cadherin. The flow cytometry analysis in HepG2 cells suggested that artemeriopolide A (1) induced G0/G1 cell cycle arrest with the percentage of cells in the G0/G1 phase ranging from 47.1% to 50.5%, 51.2%, and 54.5% and promoted cell apoptosis with apoptosis ratios from 4.8% to 6.1%, 8.2%, and 9.8%.

Direct α-C(sp³)–H alkylation of hydroaminoalkylation (HAA) catalyzed by ^tBuOK/DMSO/O₂ from α-aryl benzylamines with styrenes is reported. The reaction has delivered diverse selectively substituted amines and N-heterocycles under mild conditions. Mechanism studies have shown that α-aminoalkyl radicals act as intermediates and hydrogen atom transfer (HAT) plays a crucial role in the ^tBuOK/DMSO/O₂ system.

A novel cascade approach is presented for the synthesis of FSO₂-functionalized tetrahydropyridines from propargyl alcohols, FSO₂Cl, and anilines. This strategy successively involves radical fluorosulfonylation of the alkyne, C(sp³)–H fluorosulfonylvinylation, enamine formation, and intramolecular aza-Michael addition. Notably, the fluorosulfonyl radical can be generated efficiently via simple blue light irradiation of an electron donor–acceptor (EDA) complex between propargyl alcohols and FSO₂Cl, which requires no base, catalyst, and additive. The versatile follow-up derivatizations allow rapid ligation of tetrahydropyridines with other bioactive molecules that will be of value for drug discovery.

An efficient and straightforward strategy for the divergent synthesis of trifluoromethyl-substituted (dihydro)pyrimidoindolones via Rh(iii)-catalyzed C–H activation/annulation of N-carbamoylindoles with CF₃-imidoyl sulfoxonium ylides has been achieved. The cascade reaction might proceed through a C–H imidoylmethylation, tautomerization and intramolecular nucleophilic addition sequence. A wide range of functionalized pyrimidoindolone derivatives were constructed in good to excellent yields under redox-neutral conditions.

Frustrated radical pairs (FRP) are expected to effectively combine radical chemistry and the synergistic effects of a Lewis acid (LA) and Lewis base (LB), but this area is still in its primary stage. Here, we present a strategy for the generation of the [PhN˙⁺Me₂][B(C₆F₅)₃˙⁻] FRP using B(C₆F₅)₃ as the LA and PhNMe₂ as the LB. This FRP can initiate the efficient atom-transfer radical addition (ATRA) of different perfluoroalkyl halides to a variety of alkenes, furnishing a series of fluoroalkylated compounds in high regioselectivity and high-to-excellent product yields. This method exhibits broad substrate scope, 100% atom economy and good functional group compatibility. Systematic mechanistic studies (i.e., radical inhibitor and radical clock studies) and detailed experimental data coupled with structural characterizations led to a proposed reaction mechanism.