Beilstein Journal of Organic Chemistry最新文献

Selectivity in radical chain oligomerizations involving [1.1.1]propellane - i.e., to make [n]staffanes - has been notoriously challenging to control when n > 1 is desired. Herein, we report selective syntheses of SF₅- and CF₃SF₄-containing [2]staffanes from SF₅Cl and CF₃SF₄Cl, demonstrating cases whereby oligomerization is preferentially truncated after incorporation of two bicyclopentane (BCP) units. Synthetic and computational studies suggest this phenomenon can be attributed to alternating radical polarity matching. In addition, single-crystal X-ray diffraction (SC-XRD) data reveal structurally interesting features of the CF₃SF₄-containing [2]staffane in the solid state.

The chemistry of hypervalent iodine (HVI) reagents has gathered increased attention towards the synthesis of a wide range of chemical structures. HVI reagents are characterized by their diverse reactivity as oxidants and electrophilic reagents. In addition, they are inexpensive, non-toxic and considered to be environmentally friendly. An important application of HVI reagents is the synthesis of halogenated cyclic compounds, in particular, the intramolecular HVI-mediated halocyclisation of alkenes using carbon, oxygen, nitrogen or sulfur nucleophiles. Herein, we describe the examples reported in the literature, which are organised by the different halogens involved and the internal nucleophiles.

This review provides an overview of recent progress made in the field of catalysis using metal-free tetrapyrrolic macrocycles, focusing on calix[4]pyrroles, porphyrins and corroles, which are structurally related to porphyrins. Calix[4]pyrroles are versatile receptors in supramolecular chemistry while porphyrins are considered as 'pigment of life' due to their role in vital biological processes. Beyond their natural functions, synthetic porphyrins have been applied in various fields, including organometallic catalysis, dye-sensitized solar cells, sensing, artificial olfactory systems, photodynamic therapy (PDT), anticancer drugs, biochemical probes, and electrochemical devices. Relevant examples of these two pyrrolic macrocycles as metal-free organocatalysts, photocatalysts, and electrocatalysts are presented here. The effect of macrocyclic structural modifications such as their functionalization with different substituents, distortion from planarity, conformational flexibility and rigidity towards catalytic activity are presented, highlighting the potential of these two macrocycles as metal-free catalysts.

A series of 1,5-disubstituted tetrazole-indole hybrids were synthesized via a high-order multicomponent reaction consisting of an Ugi-azide/Pd/Cu-catalyzed hetero-annulation cascade sequence. This operationally simple one-pot protocol allowed high bond-forming efficiency and creating six new bonds (two C-C, three C-N, and one N-N). Additionally, the products were evaluated against breast cancer MCF-7 cells, finding moderate activity in the compounds substituted with fluorine and chlorine.

Distilled propargyltrichlorosilane with >99% isomeric purity was prepared for the first time, and its asymmetric catalytic regiospecific addition reaction to aldehydes was developed through a systematic catalyst structure-reactivity and selectivity relationship study. The observed catalyst structure-enantioselectivity relationship of the present allenylation reaction was found exactly opposite to that of the analogous allylation reaction. The method provided eleven α-allenic alcohols in 22-99% yield with 61:39-92:8 enantiomeric ratios. Furthermore, possible mechanisms of propargyl-allenyl isomerization of propargyltrichlorosilane were computationally investigated.

The photochromic norbornadiene/quadricyclane pair is a promising system for molecular solar thermal (MOST) energy storage, with which solar energy may be converted, stored, and released as heat in one integral molecular system. Herein, we present the synthesis of mono-, bis-, and tris-norbornadiene derivatives with alkynylbenzene and alkynylnaphthalene core units, along with studies of their photochemical properties. The target compounds were synthesized by Sonogashira-Hagihara coupling reactions of 2-bromonorbornadiene and the corresponding arylacetylenes. The norbornadienes showed absorption maxima in the range of 310-345 nm and long-wavelength zero onsets of up to 420 nm. The photoisomerization quantum yields were as high as 59% per photoisomerization event and the resulting quadricyclanes showed half-lives of up to 8 h at room temperature. Furthermore, the norbornadienes were transformed quantitatively into their quadricyclane photoproducts by irradiation with green light (520 nm) in the presence of a photosensitizer.

Bioactivity-guided fractionation (BGF) has historically been a fruitful natural product discovery workflow. However, it is plagued by increasing rediscovery rates in recent years and new methods capable of exploring the natural product chemical space more broadly and more efficiently is in urgent need. Chemical structure metagenomics as one such method is the theme of this Perspective. It emphasizes a chemical-structure-centered viewpoint toward natural product research. Key to chemical structure metagenomics is the ability to predict the structure of a natural product based on its biosynthetic gene sequences, which facilitated the discovery of numerous new bioactive molecules and helped uncover oversampled/underexplored niches of decades of BGF based discovery. While microbial nonribosomal peptides have been the focus of chemical structure metagenomics efforts thus far, it is in principle applicable to other natural product families. The future outlook of this new approach will also be discussed.

Owing to their dynamic natures, rotaxane-based polymers are attractive motifs for developing stimuli-responsive materials. However, the accurate control of the rotaxane structure, which can be achieved via multistep synthesis, is key to utilizing the material. Concurrently, implementing a scale-up synthesis procedure to exploit the application potential of rotaxane-based polymers induces structural ambiguities, thereby presenting a significant trade-off between realizing inexpensive production and defined structures. To overcome this rotaxane-synthesis challenge, cyclodextrin (CD) can be employed as a promising alternative owing to its low production cost. Thus, this study presents an overview of the precise synthesis of CD-based rotaxane and its application to polymers to simultaneously ensure inexpensive production and realize defined structures.

A facile method for the synthesis of arylidene derivatives of pyrindane - (E)-7-arylmethylene-2-chloro-6,7-dihydro-5H-cyclopenta[b]pyridine-3,4-dicarbonitriles - was developed. Tunable full-color emission was achieved for the synthesized push-pull molecules, solely by changing donor groups while keeping both the conjugated system and acceptor part of the molecule unchanged. This represents a rare approach for the design of such fluorophores. Arylidene derivatives of pyrindane were found to be efficient fluorescent dyes showing a moderate to high emission quantum yield. The push-pull molecules were also characterized by a dual-state emission (in solution and in the solid state). Emission maxima ranged from 469 to 721 nm in solution depending on the solvent and type of donor substituent, and from 493 to 767 nm in the solid state. For the arylidene derivative of pyrindane with a dimethylamino group, it was shown that fluorescence can be changed by the action of an acid both in solution and in the solid state.

Organic peroxides have become sought-after functionalities, particularly following the multi-tone consumption in polymer production and success in medicinal chemistry. The selective introduction of a peroxide fragment at different positions on the target molecule is a priority in the modern reaction design. The pioneering Kharasch-Sosnovsky peroxidation became the basic universal platform for the development of peroxidation methods, with its great potential for rapid generation of complexity due to the ability to couple the resulting free radicals with a wide range of partners. This review discusses the recent advances in the radical Kharasch-type functionalization of organic molecules with OOR fragment including free-component radical couplings. The discussion has been structured by the type of the substrate of radical peroxidation: C(sp ³ )-H substrates; aromatic systems; compounds with unsaturated C-C or C-Het bonds.