Mechanochemical Synthesis of α-halo Alkylboronic Esters.

α-halo alkylboronic esters, acting as ambiphilic synthons, play a pivotal role as versatile intermediates in fields like pharmaceutical science and organic chemistry. The sequential transformation of carbon-boron and carbon-halogen bonds into a broad range of carbon-X bonds allows for programmable bond formation, facilitating the incorporation of multiple substituents at a single position and streamlining the synthesis of complex molecules. Nevertheless, the synthetic potential of these compounds is constrained by limited reaction patterns. Additionally, the conventional methods often necessitate the use of bulk toxic solvents, exhibit sensitivity to air/moisture, rely on expensive metal catalysts, and involve extended reaction times. In this report, a ball milling technique is introduced that overcomes these limitations, enabling the external catalyst-free multicomponent coupling of aryl diazonium salts, alkenes, and simple metal halides. This approach offers a general and straightforward method for obtaining a diverse array of α-halo alkylboronic esters, thereby paving the way for the extensive utilization of these synthons in the synthesis of fine chemicals.

Zinc Promoted Cross-Electrophile Sulfonylation to Access Alkyl-Alkyl Sulfones.

The transition metal-catalyzed multi-component cross-electrophile sulfonylation, which incorporates SO2 as a linker within organic frameworks, has proven to be a powerful, efficient, and cost-effective means of synthesizing challenging alkyl-alkyl sulfones. Transition metal catalysts play a crucial role in this method by transferring electrons from reductants to electrophilic organohalides, thereby causing undesirable side reactions such as homocoupling, protodehalogenation, ß-hydride elimination, etc. It is worth noting that tertiary alkyl halides have rarely been demonstrated to be compatible with current methods owing to various undesired side reactions. In this work, a zinc-promoted cross-electrophile sulfonylation is developed through a radical-polar crossover pathway. This approach enables the synthesis of various alkyl-alkyl sulfones, including 1°-1°, 2°-1°, 3°-1°, 2°-2°, and 3°-2° types, from inexpensive and readily available alkyl halides. Various functional groups are well tolerated in the work, resulting in yields of up to 93%. Additionally, this protocol has been successfully applied to intramolecular sulfonylation and homo-sulfonylation reactions. The insights gained from this work shall be useful for the further development of cross-electrophile sulfonylation to access alkyl-alkyl sulfones.

Green synthesis of non-isocyanate hydroxyurethane and its hybridization with carboxymethyl cellulose to produce films.

Non-isocyanate polyurethanes (NIPUs) have attracted increasing attention as a sustainable alternative to conventional isocyanate-based polyurethanes. This study synthesized non-isocyanate hydroxyurethanes (NIHUs) through an addition reaction between propylene carbonate (PC) and 1,2-ethylenediamine (EDA). The resulting NIHU was then hybridized with carboxymethyl cellulose (CMC) to investigate its hybridization potential. Structural analysis through FTIR, NMR, and XRD confirmed the crystalline nature of NIHU, featuring urethane bonds and abundant hydroxyl groups. It was found that NIHU and CMC interacted by forming hydrogen bonds between hydroxyl groups of NIHU and carboxyl groups of CMC, resulting in a dense CMC/NIHU hybrid structure. NMR and XRD analyses revealed changes in the hybrids' chain mobility, the Young's modulus of the hybrid with 30 % NIHU content decreased from 1627 MPa to 502 MPa relative to CMC, and the elongation at break increased from 4.44 % to 17.2 %. Increasing the concentration of NIHU in CMC reduced the hydrophobicity, in terms of water contact angle, from 70° to 41.7°. The simplicity of the synthesis method for NIHU, coupled with the desirable structure, strength, and balanced flexibility of CMC/NIHU hybrids, is expected to facilitate the production of NIHU-rich hybrids and increase their application in packaging.

Recent Advancements in Metal-Catalyst-Free Multicomponent Radical Sulfonylation of Alkynes.

Vinyl sulfones are crucial building blocks in synthetic chemistry and core structural units of pharmaceutically active molecules, thus extensive investigations have been conducted on the construction of these skeletons. In contrast to the classical synthetic approaches, the radical sulfonylation of alkynes for producing vinyl sulfones has garnered considerable interest because of its mild conditions and high efficiency. Radical sulfonation of alkynes typically begins with the sulfonyl radical attacking the alkynes, followed by further functionalization. Moreover, the association of metal-catalyst-free systems with multicomponent reactions (MCRs) offers an environmentally friendly pathway for efficiently constructing complex scaffolds from readily available partners. However, there is no comprehensive review summarizing the advancements in metal-catalyst-free multicomponent radical sulfonylation of alkynes. Hence, we provide a categorical overview based on the objects of sulfonylation of alkynes (hydrosulfonylation, carbosulfonylation, aminosulfonylation, oxysulfonylation, sulfosulfonylation, selenosulfonylation, and iodosulfonylation), along with interpretations of the reaction mechanisms.

Catalyst-Free Visible Light-Driven Hydrosulfonylation of Alkenes and Alkynes with Sulfonyl Chlorides in Water.

A convenient and sustainable method for synthesizing sulfonyl-containing compounds through a catalyst-free aqueous-phase hydrosulfonylation of alkenes and alkynes with sulfonyl chlorides under visible light irradiation is presented. Unactivated alkenes, electron-deficient alkenes, alkyl and aryl alkynes can be hydrosulfonylated with various sulfonyl chlorides at room temperature with excellent yields and geometric selectivities by using tris(trimethylsilyl)silane as a hydrogen atom donor and silyl radical precursor to activate sulfonyl chlorides. Mechanistic studies revealed that the photolysis of tris(trimethylsilyl)silane in aqueous solution to produce silyl radical is crucial for the success of this reaction.

Sustainable Synthesis through Catalyst-Free Photoinduced Cascaded Bond Formation.

The beginning of photochemical reactions revolutionized synthetic chemistry through sustainable practices. This review explores cutting-edge developments in leveraging light-induced processes for generating cascaded C-C and C-hetero bonds without catalysts. Significantly, catalyst-free photoinduced methodologies have garnered considerable attention, especially in the creation of varied heterocyclic frameworks for drug design and the synthesis of natural products. The article delves into underlying mechanisms, addresses limitations, and evaluates various methodologies, emphasizing the potential of photocatalyst and transition metal-free photochemical reactions to enhance sustainability. Divided into two sections, it covers recent strides in C-C and C-heteroatom and multiple C-heteroatom bond formation reactions.

Ultrafast and efficient continuous flow organic synthesis with a modified extruder-grinder system.

The study introduces a groundbreaking continuous system that combines an extruder and grinder to enable catalyst-free and solvent-free reactions under mild conditions. This temperature-controlled system facilitates the synthesis of highly functionalized chromenes, which have valuable applications in generating combinatorial libraries and complex target molecules. The newly developed mill extruder machine offers several advantages for industrial production on a large scale. It effectively reduces waste, saves energy, and enhances time efficiency. This system represents a significant advancement in the field, providing a new strategy for one-pot synthesis of various types of highly functionalized spirooxindoles and chromenes. Remarkably, these reactions can be accomplished within a short timeframe of 2-10 min, yielding impressive results of 75-98%. The results demonstrate superior performance compared to traditional reaction methods, making it an appealing tool and hotspot area of research in green chemistry.

Solvent- and Catalyst-Free Synthesis of gem-Difluorinated and Polyfluoroarylated Compounds with Nucleophilic or Electrophilic Fluorine-Containing Reaction Partners, Respectively.

A novel, efficient and environmentally friendly solvent-free and catalyst-free approach for the synthesis of structurally diverse gem-difluorinated and polyfluoroarylated derivatives with readily available nucleophilic and electrophilic fluorine-containing reaction partners, difluoroenoxysilane and pentafluorobenzaldehyde, is described. This neat protocol is induced by the direct hydrogen-bond interactions between fluorinated and non-fluorinated reactants without the use of heavy metal catalysts or volatile organic solvents and with no need for column chromatographic separation for most cases.

Catalyst-Free Cardanol-Based Epoxy Vitrimers for Self-Healing, Shape Memory, and Recyclable Materials.

Bio-based vitrimers present a promising solution to the issues associated with non-renewable and non-recyclable attributes of traditional thermosetting resins, showcasing extensive potential for diverse applications. However, their broader adoption has been hindered by the requirement for catalyst inclusion during the synthesis process. In this study, a cardanol-based curing agent with poly-hydroxy and tertiary amine structures was prepared by a clean synthetic method under the theory of click chemistry. The reaction of a cardanol-based curing agent with diglycidyl ether of bisphenol A formed catalyst-free, self-healing, and recyclable bio-based vitrimers. The poly-hydroxy and tertiary amine structures in the vitrimers promoted the curing of epoxy-carboxylic acid in the cross-linked network and served as internal catalysts of dynamic transesterification. In the absence of catalysts, the vitrimers network can achieve topological network rearrangement through dynamic transesterification, exhibiting excellent reprocessing performance. Moreover, the vitrimers exhibited faster stress relaxation (1500 s at 180 °C), lower activation energy (92.29 kJ·mol-1) and the tensile strength of the recycled material reached almost 100% of the original sample. This work offers a new method for preparing cardanol-based epoxy vitrimers that be used to make coatings, hydrogels, biomaterials, adhesives, and commodity plastics in the future.

Mechanical Properties and Degradation Rate of Poly(Sorbitol Adipate-Co-Dioladipate) Copolymers Obtained with a Catalyst-Free Melt Polycondensation Method.

A new family of polyester-based copolymers-poly(sorbitol adipate-co-ethylene glycol adipate) (PSAEG), poly(sorbitol adipate-co-1,4 butane diol adipate) (PSABD), and poly (sorbitol adipate-co-1,6 hexane diol adipate) (PSAHD)-was obtained with a catalyst-free melt polycondensation procedure using the multifunctional non-toxic monomer sorbitol, adipic acid, and diol, which are acceptable to the human metabolism. Synthesized polyesters were characterized by FTIR and 1H NMR spectroscopy. The molecular weight and thermal properties of the polymers were determined by MALDI mass spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis. The degradation rate was investigated, at 37 °C, in 0.1M NaOH (pH 13) and in phosphate-buffered solution (PBS) at pH 7.4. It was found that the polymers degraded faster in NaOH (i.e., in a day) compared to their degradation in PBS, which was much slower (in a week). The highest degradation rate was noticed for the PSAEG sample in both media, whereas PSAHD was the most stable polymer at pH 7.4 and 13. A reduced hydrophilicity of the polymers with diol length was indicated by low swelling percentage and sol content in water and DMSO. Mechanical studies prove that all the polymers are elastomers whose flexibility increases with diol length, shown by the increase in percentage of elongation at break and the decrease in tensile stress and Young's modulus. These biodegradable copolymers with adaptable physicochemical characteristics might be useful for a broad variety of biological applications by merely varying the length of the diol.

Mild and Efficient Preparation of N-Heterocyclic Organic Molecules by Catalyst-free and Solvent-free Methods.

AIMS: The small organic molecular compounds with biological activity containing C-C and C-N or C-O bonding were efficiently prepared without catalyst and solvent in the hydrothermal synthesis reactor. OBJECTIVES: Our goal was to explore new applications for the more environmentally friendly and efficient synthesis of bis(indolyl)methyl, xanthene, quinazolinone, and N-heterocyclic derivatives in hydrothermal synthesis reactors under solvent-free and catalyst-free conditions. METHODS: A greener and more efficient method was successfully developed for the synthesis of bis(indolyl)methyl, heteroanthracene, quinazolinone, and N-heterocyclic derivatives using a hydrothermal synthesis reactor in a solvent- and catalyst-free manner. RESULTS: In a hydrothermal synthesis reactor, bis(indoyl)methyl, xanthene, quinazolinone, and N-heterocyclic derivatives were synthesized without catalysts and solvents. CONCLUSION: Overall, it is proved once again that the catalyst-free and solvent-free synthesis method has universal value and is a more ideal and environmentally friendly new method, especially the hydrothermal reactor for synthesis.

The catalyst free synthesis of dibenzo[a,j]acridine and its applications in bioimaging of BF3 in HeLa cells.

In this paper, we discuss how tetrahydrodibenzo[a,j]acridine (4-HA) loses its hydrogen, which makes dibenzo[a,j]acridine (ARM) and also how 4-HA can be synthesized effectively using 2-tetralone in high yield. Dehydrogenative condensation and dehydrogenation are the two processes that make up the overall reaction of this synthetic approach. In addition, the presence of BF3 caused a remarkable fluorescence shift in ARM. Test paper analysis was used for examining the practical usefulness of ARM, which can be seen under UV light, resulting in this unique phenomenon. The fluorescent bio imaging experiment demonstrates that the sensor ARM has the capability to detect BF3 in living HeLa cells.

Visible-light promoted catalyst-free (VLCF) multi-component synthesis of spiro indolo-quinazolinone-pyrrolo[3,4-a]pyrrolizine hybrids: evaluation of in vitro anticancer activity, molecular docking, MD simulation and DFT studies.

A new and highly efficient visible-light-promoted catalyst free (VLCF) strategy for neat and clean synthesis of spiro indolo-quinazolinone-pyrrolo[3,4-a]pyrrolizine hybrids (6a-d) has been introduced. We have performed visible-light triggered 1,3-Dipolar cycloaddition reaction of maleimide (5a-d) with azomethine ylide generated in situ derived from tryptanthrin (3) and L-proline (4) to obtain desired products (6a-d) in good to excellent yield. Authentication and characterization of product was done using various spectroscopic techniques such as IR, 1H NMR, 13C NMR, Mass spectrometry and single crystal XRD analysis. To explain the reaction spontaneity, product stability, reactivity as well as possible mode of the interaction a quantum chemical investigation was performed and depicted through DFT studies. The synthesized compound 6a was also evaluated for anti-proliferative activity against a panel of five cancer cell lines (MCF-7, MDA-MB-231, HeLa, PC-3 and Ishikawa) and normal human embryonic kidney (HEK-293) cell line by using MTT assay. Compound 6a showed very good in vitro anti-proliferative activity (IC50  = 6.58-17.98 µM) against four cancer cell lines and no cytotoxicity against normal HEK-293. In order to evaluate the anticancer potential of compounds 6a-d, molecular docking was performed against wild type and mutant EGFR. The results suggest that all the compounds occupied the active site of both enzymes, with a strong binding energy (-10.2 to -11.5 kcal/mol). These results have been confirmed by molecular dynamics simulation by evaluating root mean square deviation (RMSD) and root mean square fluctuation (RMSF), along with principal component analysis (PCA).Communicated by Ramaswamy H. Sarma.

In silico and in vitro evaluation of newly synthesized pyrazolo-pyridine fused tetrazolo-pyrimidines derivatives as potential anticancer and antimicrobial agents.

Diversely functionalized pyrazolo-pyridine fused tetrazolo-pyrimidines 10aa-am and 10ba-bn were successfully synthesized via a catalyst-free synthetic protocol with moderate to very good yields. The compounds were evaluated for cytotoxicity against MCF-7 and HEK-293 cells using MTT assay. Among the tested compounds, 10ab (IC50- 23.83 µM) and 10ah (IC50- 23.30 µM) demonstrated the highest potency against MCF-7 cells, while 10bc (IC50- 14.46 µM) and 10bh (IC50- 2.53 µM) exhibited excellent cytotoxicity against HEK-293 cells. Additionally, antibacterial screening was performed against three Gram-negative bacteria (E. coli, P. aeruginosa, and S. enterica) and three Gram-positive bacteria (S. aureus, B. megaterium, and B. subtilis) using broth dilution method, while antifungal activity was assessed against three fungal strains (A. niger, Penicillium, and S. cerevisiae) using agar well diffusion method. In antimicrobial screening, the majority of the compounds demonstrated significant antibacterial efficacy compared to antifungal activity. We also conducted comprehensive computational studies, including DFT calculations, molecular docking and dynamics, and drug-likeness assessments. In the DFT study, compounds 10ac and 10bc displayed stable conformations, indicating their potential for higher therapeutic activity. Molecular docking analyses revealed compelling interactions, with compound 10ah demonstrating docking score -7.42 kcal/mol against catalytical domain PARP1 (PDB ID: 7KK4) and 10bh exhibiting a best docking score -10.77 kcal/mol against human corticotropin-releasing factor receptor 1 (PDB ID: 4Z9G). A 100 ns molecular dynamics (MD) simulation study of compounds 10ah and 10bh revealed the stable conformation and binding energy in a stimulating environment. In drug-likeness assessments, both the compounds 10ah and 10bh adhere all the established guidelines.Communicated by Ramaswamy H. Sarma.

Supercritical transesterification of vegetable oil and ethanol: temperature and residence time effects on phase formation and water content

Supercritical transesterification has emerged as a readily available alternative for biodiesel production since no catalyst is required, thereby generating fewer waste products. In this research, the supercritical transesterification of refined vegetable oil and aqueous ethanol was carried out at temperatures 400 to 480 °C and a 12:1 ethanol to oil molar ratio, to assess the effect of temperature and residence time in the formation of a homogeneous phase, effluent appearance and increased water content derived from glycerol etherification. The results showed that water was produced at temperatures higher than 400 °C, as expected from the occurrence of glycerol etherification, and that prolonged times resulted in gas and soot formation, indicating esters decomposition. Through water mass balances, it was possible to identify the set of operation conditions in which the water formed from glycerol etherification matched with the maximum expected according to the proposed reaction scheme.

La transesterificación supercrítica se ha propuesto como una alternativa para la producción de biodiesel ya que no requiere catalizador de esta manera se generan menos residuos. En esta investigación, la transesterificación supercrítica de aceite vegetal refinado y etanol acuoso se llevó a cabo a temperaturas en el rango 400 a 480 °C y relación molar etanol a aceite de 12:1, para evaluar el efecto de la temperatura y el tiempo de residencia en la formación de una fase homogénea, apariencia del efluente e incremento del contenido de agua resultado de las reacciones de eterificación del glicerol. Los resultados mostraron que se produjo agua a temperaturas mayores a 400°C, atribuida a la eterificación del glicerol, y que tiempos de residencia prolongados resultaron en formación de gas y hollín, indicativo de reacciones de descomposición de esteres. A través de balances de masa, fue posible identificar el conjunto de condiciones de operación a las cuales el agua formada por la eterificación del glicerol coincide con el valor máximo esperado de acuerdo con el esquema de reacción propuesto.

A transesterificação supercrítica foi proposta como uma alternativa para a produção de biodiesel porque não requer catalisador e, dessa forma, gera menos resíduos. Nesta pesquisa, a transesterificação supercrítica de aceite vegetal refinado e etanol acuoso foi conduzida a temperaturas entre 400 e 480 °C e uma relação molar de etanol e aceite de 12: 1, para avaliar o efeito da temperatura e do tempo de residência na formação de uma fase homogênea, apariência do efluente e aumento do conteúdo de água resultante das reações de eterificação do glicerol. Os resultados mostraram que se produziu água a temperaturas maiores que 400°C, atribuída à eterificação do glicerol, e que os tempos de residência prolongados resultaram na formação de gás e hollín, indicativo de reações de decomposição de ésteres. Por meio de balanças de massa, foi possível identificar o conjunto de condições de operação em que a água formada pela eterificação do glicerol coincide com o valor máximo esperado de acordo com o esquema de reação proposto.

Catalyst-Free Trans-Selective Oxyiodination and Oxychlorination of Alkynes Employing N-X (Halogen) Reagents.

ß-halogenated enol esters and ethers are versatile building blocks in organic synthesis, which has attracted increasing attention. In this study, we report the facile trans-oxyiodination and oxychlorination of alkynes, leading to the direct construction of versatile halogenated enol esters and ethers. This transformation features an easy operation, optimal atomic economy, a strong functional group tolerance, broad substrate scope, and excellent trans-selectivity. Employing highly electrophilic bifunctional N-X (halogen) reagents was the key to achieving broad reaction generality. To our knowledge, this transformation represents the first oxyhalogenation system employing N-X (halogen) reagents as both oxylation and halogenation sources.

Low-Vacuum Catalyst-Free Physical Vapor Deposition and Magnetotransport Properties of Ultrathin Bi2Se3 Nanoribbons.

In this work, a simple catalyst-free physical vapor deposition method is optimized by adjusting source material pressure and evaporation time for the reliable obtaining of freestanding nanoribbons with thicknesses below 15 nm. The optimum synthesis temperature, time and pressure were determined for an increased yield of ultrathin Bi2Se3 nanoribbons with thicknesses of 8-15 nm. Physical and electrical characterization of the synthesized Bi2Se3 nanoribbons with thicknesses below 15 nm revealed no degradation of properties of the nanoribbons, as well as the absence of the contribution of trivial bulk charge carriers to the total conductance of the nanoribbons.

Photocatalyst- and Transition Metal-Free Light-Induced Borylation Reactions.

The increasing global warming concerns have propelled a surge in the demand for sustainable energy sources within the domain of synthetic organic chemistry. A particularly prominent area of research has been the development of mild synthetic strategies for generating heterocyclic compounds. Heterocyclic compounds containing boron have notably risen to prominence as pivotal reagents in a myriad of organic transformations, showcasing their wide-ranging applicability. This comprehensive review is aimed at collecting the literature pertaining to borylation reactions induced by light, specifically focusing on photocatalyst-free and transition metal-free methodologies. The central emphasis is on delving into selective mechanistic investigations. The amalgamation and analysis of these research insights elucidate the substantial potential inherent in eco-friendly approaches for synthesizing heterocyclic compounds, thus propelling the landscape of sustainable organic chemistry.

Selective and scalable oxygenation of heteroatoms using the elements of nature: air, water, and light.

Sustainable oxidation protocols aim to provide an environmentally friendly and cost-effective method for the production of various chemicals and materials. The development of such protocols can lead to reduced energy consumption, fewer harmful byproducts, and increased efficiency in industrial processes. As such, this field of research is of great importance and interest to both academia and industry. This work showcases a sustainable and catalyst-free oxidation method for heteroatoms (e.g., S, P, and Se) using only air, water and light. An additional reaction pathway is proposed in which the incorporated oxygen on the heteroatoms originates from water. Furthermore, the addition of certain additives enhances productivity by affecting kinetics. The industrial potential is demonstrated by conveniently transferring the batch protocol to continuous flow using the HANU flow reactor, indicating scalability and improving safety.

Construction of N-Ferrocene Substituted Benzodihydrooxazoles via a Catalyst-Free Aza-Michael Addition/C(sp3)-O Bond Formation Tandem Reaction.

A catalyst-free aza-Michael addition/C(sp3)-O bond formation tandem reaction of substituted amino ferrocenes with quinone esters was developed, which provided a green and efficient strategy for the construction of a C(sp3)-O bond from C(sp3)-H, and a series of N-ferrocene-substituted benzodihydrooxazoles were smoothly produced in moderate to excellent yields (up to >99% yield). The mechanism experiments showed that quinone esters performed as both substrate and oxidant. The salient features of this transformation include good functional group tolerance, broad substrate scope and mild conditions.