Bicyclic Products Research Articles

The impact of Lewis acid variation on reactions with di-tert-butyl diazo diesters.

Reactions of (tBuO2CN)2 with Lewis acids and FLPs have previously been shown to prompt the formation of diazene compounds. In this work, we show that the reaction of (tBuO2CN)2 with 9-BBN leads to a bicyclic heterocyclic product (tBuOCO(BBN)CN)21. In contrast, the reactions of (tBuO2CN)2 with BF3 or [Et3Si][B(C6F5)4] lead to the isolation of [tBuNHNH2tBu][BF4] 2 and [tBuN(H)NtBu][B(C6F5)4] 3, respectively. The mechanism for the formation of 2 is probed computationally, demonstrating that steric and electronic considerations of the Lewis acid impact the reaction pathway.

Mechanochemistry of Pterodactylane.

Pterodactylane is a [4]-ladderane with substituents on the central rung. Comparing the mechanochemistry of the [4]-ladderane structure when pulled from the central rung versus the end rung revealed a striking difference in the threshold force of mechanoactivation: the threshold force is dramatically lowered from 1.9 nN when pulled on the end rung to 0.7 nN when pulled on the central rung. We investigated the bicyclic products formed from the mechanochemical activation of pterodactylane experimentally and computationally, which are distinct from the mechanochemical products of ladderanes being activated from the end rung. We compared the products of pterodactylane's mechanochemical and thermal activation to reveal differences and similarities in the mechanochemical and thermal pathways of pterodactylane transformation. Interestingly, we also discovered the presence of elementary steps that are accelerated or suppressed by force within the same mechanochemical reaction of pterodactylane, suggesting rich mechanochemical manifolds of multicyclic structures. We rationalized the greatly enhanced mechanochemical reactivity of the central rung of pterodactylane and discovered force-free ground state bond length to be a good low-cost predictor of the threshold force for cyclobutane-based mechanophores. These findings advance our understanding of mechanochemical reactivities and pathways, and they will guide future designs of mechanophores with low threshold forces to facilitate their applications in force-responsive materials.

Cyclization mechanism of monoterpenes catalyzed by monoterpene synthases in dipterocarpaceae

Monoterpenoids are typically present in the secretory tissues of higher plants, and their biosynthesis is catalyzed by the action of monoterpene synthases (MTSs). However, the knowledge about these enzymes is restricted in a few plant species. MTSs are responsible for the complex cyclization of monoterpene precursors, resulting in the production of diverse monoterpene products. These enzymatic reactions are considered exceptionally complex in nature. Therefore, it is crucial to understand the catalytic mechanism of MTSs to elucidate their ability to produce diverse or specific monoterpenoid products. In our study, we analyzed thirteen genomes of Dipterocarpaceae and identified 38 MTSs that generate a variety of monoterpene products. By focusing on four MTSs with different product spectra and analyzing the formation mechanism of acyclic, monocyclic and bicyclic products in MTSs, we observed that even a single amino acid mutation can change the specificity and diversity of MTS products, which is due to the synergistic effect between the shape of the active cavity and the stabilization of carbon-positive intermediates that the mutation changing. Notably, residues N340, I448, and phosphoric acid groups were found to be significant contributors to the stabilization of intermediate terpinyl and pinene cations. Alterations in these residues, either directly or indirectly, can impact the synthesis of single monoterpenes or their mixtures. By revealing the role of key residues in the catalytic process and establishing the interaction model between specific residues and complex monoterpenes in MTSs, it will be possible to reasonably design and engineer different catalytic activities into existing MTSs, laying a foundation for the artificial design and industrial application of MTSs.

Intramolecular interactions and the neutral loss of ammonia from collisionally activated, protonated ω-aminoalkyl-3-hydroxyfurazans.

Gas phase fragmentation reactions of monoprotonated 4-(3-aminopropyl)- and 4-(4-aminobutyl)-3-hydroxyfurazan were investigated to examine potential interactions between functional groups. The two heterocyclic alkyl amines were ionized by electrospray ionization (ESI, positive mode) and fragmented using tandem mass spectrometry (MS/MS). The fragmentation pathways were characterized using pseudo MS3 experiments, precursor-ion scans, and density functional computations. For both heterocyclic ions, loss of ammonia was the only fragmentation process observed at low collision energies. Computational analysis indicated that the most feasible mechanism was intramolecular nucleophilic displacement of ammonia from the protonated ω-aminoalkyl side chain by N5 of the furazan ring. The alkylated nitrogen in the resulting bicyclic product ion facilitated N-O bond cleavage; subsequent neutral losses of nitric oxide (NO) and carbon monoxide (CO) occurred by homolytic bond cleavages. Next in the multistep sequence, neutral loss of ethylene from a radical cation was observed. A less favorable, competing fragmentation pathway of protonated 4-(3-aminopropyl)-3-hydroxyfurazan was consistent with cleavage of the 3-hydroxyfurazan ring and losses of NO and CO. Overall, the similar fragmentation behavior found for protonated 4-(3-aminopropyl)- and 4-(4-aminobutyl)-3-hydroxyfurazan differed from that previously characterized for furazan analogs with shorter alkyl chains. These observations demonstrate that a small change in the structure of multifunctional, heterocyclic alkyl amines may significantly influence interactions between distinct functional groups and the nature of the fragmentation process.

HPW/MCM-41 catalytic Simmons-Smith cyclopropanation of olefins for synthesis of high-energy–density fuel

Simmons-Smith cyclopropanation commonly promoted by CF3COOH is one important method for transforming olefin into high-energy–density cyclopropyl fuel, but it brings problems such as high cost and harm to environment. In this work, a series of highly active solid acid catalysts HPW/MCM-41 is prepared by impregnation method for the cyclopropanation of dicyclopentadiene. The composition, structural and acidity of catalyst were characterized by TEM, XRD, NH3-TPD, etc. The 5 % HPW/MCM-41 contains more Dawson-type P2W18 (H6P2W18O62) and defective-type P2W21 (H6P2W21O71) that can provide the most abundant acid sites. This catalyst shows the best catalytic activity, the conversion and bicyclic product selectivity for cyclopropanation of dicyclopentadiene are 93.4 % and 55.7 %, respectively, both higher than that of CF3COOH. Moreover, such catalyst shows good catalytic activity for several olefin substrates, and can be recycled in several runs. This work provides a green and efficient catalyst for cyclopropanation reactions for synthesis of high-energy–density fuel, pesticide and medicine.

Decarboxylative Intramolecular [3 + 2] Cycloaddition of Cyclic Enol Carbonates: Construction of a Bicyclo[3.3.0]octanone Skeleton.

Stereoselective synthesis of bicyclic cyclopentanones was achieved by sequential Tf2O-catalyzed decarboxylation and intramolecular [3 + 2] cycloaddition reactions of cyclic enol carbonates bearing an alkene unit. Four stereogenic centers in the obtained cyclopentanone were stereoselectively constructed. This method could be applied to the synthesis of various fused bicyclic products in moderate-to-good yields.

On the Use of Asset Administration Shell for Modeling and Deploying Production Scheduling Agents within a Multi-Agent System

Industry 4.0 (I4.0) aims at achieving the interconnectivity of multiple industrial assets from different hierarchical layers within a manufacturing environment. The Asset Administration Shell (AAS) is a pilar component of I4.0 for the digital representation of assets and can be applied in both physical and digital assets, such as enterprise software, artificial intelligence (AI) agents, and databases. Multi-agent systems (MASs), in particular, are useful in the decentralized optimization of complex problems and applicable in various planning or scheduling scenarios that require the system’s ability to adapt to any given problem by using different optimization methods. In order to achieve this, a universal model for the agent’s information, communication, and behaviors should be provided in a way that is interoperable with the rest of the I4.0 assets and agents. To address these challenges, this work proposes an AAS-based information model for the description of scheduling agents. It allows multiple AI methods for scheduling, such as heuristics, mathematical programming, and deep reinforcement learning, to be encapsulated within a single agent, making it adjustable to different production scenarios. The software implementation of the proposed architecture aims to provide granularity in the deployment of scheduling agents which utilize the underlying AAS metamodel. The agent was implemented using the SARL agent-oriented programming (AOP) language and deployed in an open-source MAS platform. The system evaluation in a real-life bicycle production scenario indicated the agent’s ability to adapt and provide fast and accurate scheduling results.

Asymmetric Intramolecular Hydroalkylation of Internal Olefin with Cycloalkanone to Directly Access Polycyclic Systems.

An asymmetric intramolecular hydroalkylation of unactivated internal olefins with tethered cyclic ketones was realized by the cooperative catalysis of a newly designed chiral amine (SPD-NH2) and Pd(II) complex, providing straightforward access to either bridged or fused bicyclic systems containing three stereogenic centers with excellent enantioselectivity (up to 99% ee) and diastereoselectivity (up to >20:1 dr). Notably, the bicyclic products could be conveniently transformed into a diverse range of key structures frequently found in bioactive terpenes, such as ∆6-protoilludene, cracroson D, and vulgarisins. The steric hindrance between the Ar group of the SPD-NH2 catalyst and the branched chain of the substrate, hydrogen-bonding interactions between the N-H of the enamine motif and the C=O of the directing group MQ, and the counterion of the Pd(II) complex were identified as key factors for excellent stereoinduction in this dual catalytic process by density functional theory calculations.

Asymmetric Intramolecular Hydroalkylation of Internal Olefin with Cycloalkanone to Directly Access Polycyclic Systems

AbstractAn asymmetric intramolecular hydroalkylation of unactivated internal olefins with tethered cyclic ketones was realized by the cooperative catalysis of a newly designed chiral amine (SPD‐NH2) and PdII complex, providing straightforward access to either bridged or fused bicyclic systems containing three stereogenic centers with excellent enantioselectivity (up to 99 % ee) and diastereoselectivity (up to >20 : 1 dr). Notably, the bicyclic products could be conveniently transformed into a diverse range of key structures frequently found in bioactive terpenes, such as Δ6‐protoilludene, cracroson D, and vulgarisins. The steric hindrance between the Ar group of the SPD‐NH2 catalyst and the branched chain of the substrate, hydrogen‐bonding interactions between the N−H of the enamine motif and the C=O of the directing group MQ, and the counterion of the PdII complex were identified as key factors for excellent stereoinduction in this dual catalytic process by density functional theory calculations.

Palladium-Catalyzed Stitching of 1,3-C(sp3)-H Bonds with Dihaloarenes: Short Synthesis of (±)-Echinolactone D.

Palladium-catalyzed C(sp3)-H functionalization presents an efficient strategy to construct a variety of carbon-carbon bonds. However, application of this approach toward the preparation of five-membered benzo-fused carbocycles via the most simplifying C-H activation logic has not been realized. In this Article, we report a palladium-catalyzed annulation reaction between gem-dimethyl-containing amides and 1-bromo-2-iodoarenes that effectively constructs two Calkyl-Caryl bonds and provides access to a variety of five-membered benzo-fused compounds. In this transformation, the dihaloarene is stitched to the gem-dimethyl moiety via two sequential β-C(sp3)-H arylations utilizing the differential reactivity of the 1,2-difunctionalized electrophile. This annulation reaction is enabled by a dual-ligand system comprising of an N-acyl glycine and a pyridine-3-sulfonic acid that synergistically promotes the palladium stitching and provides the bicyclic products. This method displays a broad substrate scope and shows excellent amide compatibility. We also demonstrate the synthetic potential of this annulation by synthesizing echinolactone D.

AlCl3‐Promoted Conia‐Ene‐Related Cyclization of α,ω‐Diethylenic Ketones and 1,2‐ or 1,3‐Hydroalkenylation of Unactivated Cyclopropanes

Abstractα,β‐Unsaturated enones possessing an unactivated olefin at the ϵ‐, ζ‐ or η‐position underwent an aluminum chloride‐promoted Conia‐ene‐related cyclization, affording unsaturated decalones or hexahydroindenones in generally good yields. Cyclopropanes could be used as olefin surrogates in this process, leading to the same bicyclic products in slightly improved efficiency as the result of 1,2‐ or 1,3‐hydroalkenylation reactions. This method provided an access to a whole range of bi‐ or tricyclic enone synthons, some of which were potentially useful as odorants or in the synthesis of biologically active molecules.

Dearomative ring expansion of thiophenes by bicyclobutane insertion

Skeletal ring enlargement is gaining renewed interest in synthetic chemistry and has recently focused on insertion of one or two atoms. Strategies for heterocyclic expansion through small-ring insertion remain elusive, although they would lead to the efficient formation of bicyclic products. Here, we report a photoinduced dearomative ring enlargement of thiophenes by insertion of bicyclo[1.1.0]butanes to produce eight-membered bicyclic rings under mild conditions. The synthetic value, broad functional-group compatibility, and excellent chemo- and regioselectivity were demonstrated by scope evaluation and product derivatization. Experimental and computational studies point toward a photoredox-induced radical pathway.

Synthesis of Fused Tricyclic Amines Bearing Tetrasubstituted Carbons Using an Alkylation-Cyclization-Isomerization-3-aza-Cope Cascade Reaction.

A new cascade reaction sequence that involves alkylation, cyclization, isomerization, and 3-aza-Cope rearrangement was discovered. The stereogenic centers of the starting piperidines were transferred to the bicyclic enamine products, and a range of electron-withdrawing groups on the alkyne moieties, from ketones to amides, were tolerated under the reaction conditions. The bicyclic enamines underwent trifluoroacetic acid (TFA)-mediated cyclization to form tricyclic amines bearing tetrasubstituted carbons.

Additivity of Diene Substituent Gibbs Free Energy Contributions for Diels-Alder Reactions between Me2C=CMe2 and Substituted Cyclopentadienes.

Systematic computational studies of pericyclic Diels-Alder reactions between (H3C)2C=C(CH3)2, 1, and all permutations of substituted cyclopentadienes c-C5R1R2R3R4R5aR5b (R = H, CH3, CF3, F) allowed isolation of substitutional effects on Gibbs free energy barrier heights and reaction Gibbs free energies. "Average Substitution Gibbs Free Energy Correction" ΔG ASC# ‡/ΔG ASC# values for each substituent in each position appeared to be additive. Substituent effects on barriers showed interesting contrasts. Methyl substitution at positions 5a and 5b increased barriers significantly, while substitution at all other positions had essentially no impact. In contrast, fluoro substitution at positions 5a and 5b lowered barriers more than substitution at other positions. Trifluoromethyl substitution mixed these effects, in that substitution at positions 5a and 5b increased barriers, but substitution at other positions lowered them. Despite the variances, ΔG ASC# ‡/ΔG ASC# values allowed reliable prediction of barriers and exergonicities for reactions between 1 and highly substituted cyclopentadienes, and between 1 and cyclopentadienes with random mixtures of CH3/CF3/F substituents. ΔG ASC# ‡/ΔG ASC# values were correlated with steric considerations and quantum theory of atoms in molecules (QTAIM) calculations. Overall, the ASC values provide a resource for predicting which Diels-Alder reactions of this type should occur at rapid rates and/or give stable bicyclic products.

Obtainment of Threo and Erythro Isomers of the 6-Fluoro-3-(2,3,6,7,8,9-hexahydronaphtho[2,3-b][1,4]dioxin-2-yl)-2,3-dihydrobenzo[b][1,4]dioxine-5-carboxamide

2,6-difluorobenzamides have been deeply investigated as antibacterial drugs in the last few decades. Several 3-substituted-2,6-difluorobenzamides have proved their ability to interfere with the bacterial cell division cycle by inhibiting the protein FtsZ, the key player of the whole process. Recently, we developed a novel family of 1,4-tetrahydronaphthodioxane benzamides, having an ethoxy linker, which reached sub-micromolar MICs towards Gram-positive Staphylococcus aureus and Bacillus subtilis. A further investigation of their mechanism of action should require the development of a fluorescent probe, and the consequent definition of a synthetic pathway for its obtainment. In the present work, we report the obtainment of an unexpected bicyclic side product, 6-fluoro-3-(2,3,6,7,8,9-hexahydronaphtho[2,3-b][1,4]dioxin-2-yl)-2,3-dihydrobenzo[b][1,4]dioxine-5-carboxamide, coming from the substitution of one aromatic fluorine by the in situ formed alkoxy group, in the final opening of an epoxide intermediate. This side product was similarly achieved, in good yields, by opening the ring of both erythro and threo epoxides, and the two compounds were fully characterized using HRMS, 1H-NMR, 13C-NMR, HPLC and DSC.

Sequencing palladium-catalyzed cycloisomerization cascades in a synthesis of the gelsemine core.

Transition metal-catalyzed cycloisomerization is a powerful strategy for the construction of cyclic organic molecules, and the use of palladium catalysts can deliver a wide range of monocyclic and bicyclic products. However, applications of cycloisomerizations in complex target synthesis in which more than one cycloisomerization process is deployed in a cascade context are rare. Here we report investigations of the relative rates of two different types of ene-ynamide cycloisomerization that form fused and spirocyclic rings, and use of these results to design a sequence-controlled cascade cycloisomerization that prepares the tetracyclic core of gelsemine in a single step. Crucial to this work was an evaluation of the kinetics of each cycloisomerization in competition experiments, which revealed a key influence of the ynamide electron-withdrawing group on the cycloisomerization reaction.

Heterogeneous catalyzed isomerization of turpentine oil by ordered mesoporous materials like M41S structures

AbstractHerein, the synthesis of a structure with a porous system similar to that of molecular sieves, MCM‐41 and 48 types, with the incorporation of heteroatoms in their synthesis, is reported. The catalytic activity of these materials was tested in the isomerization reaction of turpentine oil to obtain camphene. The best results were obtained with Zn‐Al‐Si‐MCM, a mesoporous material, with a conversion of up to 96% and selectivities of 31% and 22% to camphene and 4‐carene, respectively, both of which are bicyclic products. The recycling of the catalyst was also tested, and after three cycles, no significant loss of activity was observed.

Perancangan Aplikasi penjualan Sepeda pada Toko Eco Bike Berbasis Web Menggunakan Metode Waterfall

Ecobike shop is a shop that provides and sells sport bikes and bicycle accessories products. The Ecobike shop has recently experienced some difficulties in developing sales and promotions, because the Ecobike shop still uses a sales and promotion system that is still conventional in the sense that customers still have to come to the store's sales location directly to see the condition of the bicycle product and a promotion system that only spreads brochures to customers, although it has been running well in the city of Medan but this is not optimal for today. The method applied in the eco bike sales application uses a descriptive method approach to collect the information data needed in order to be able to make a picture of the situation, event, or trend that is developing at this time.

Dual Activation Strategy to Achieve C-C Cleavage of Cyclobutanes: Development and Mechanism of Rh and Zn Cocatalyzed [4 + 2] Cycloaddition of Yne-Vinylcyclobutanones.

Reported here is the Rh and Zn cocatalyzed [4 + 2] cycloaddition of newly designed yne-vinylcyclobutanones, which can generate 5/6 or 6/6 bicyclic products with an all-carbon quaternary bridgehead center. The reaction has a broad scope and can realize chirality transfer from enantioenriched substrates to the cycloadducts. The key to the success of this [4 + 2] reaction is the introduction of a vinyl group to cyclobutanones, which helps the C-C cleavage of vinylcyclobutanones via oxidative addition. This C-C cleavage step is synergistically aided by Zn coordination to the carbonyl group of vinylcyclobutanones. Of the same importance, visual kinetic analysis and computational studies have been carried out to support the dual activation in the rate-determining C-C cleavage, to derive the rate law of the [4 + 2] reaction, to understand another role of Zn in helping the in situ generation of the cationic Rh catalyst and preventing catalyst deactivation, and to analyze the key transition states and intermediates involved.

Conversion of lignin oil and hemicellulose derivative into high-density jet fuel

Synthesizing high-density fuel from lignocellulose can not only achieve green and low-carbon development, but also expand the feedstock source of hydrocarbon fuel. Here, we reported a route of producing high-density fuel from lignin oil and hemicellulose derivative cyclopentanol through alkylation and hydrodeoxygenation. HY with SiO2/Al2O3 molar ratio of 5.3 was screened as the alkylation catalyst in the reaction of model phenolic compounds and mixtures, and the reaction conditions were optimized to achieve conversion of phenolic compounds higher than 87% and selectivity of bicyclic and tricyclic products higher than 99%. Then two phenolic pools simulating the composition of two typic lignin oils were studied to validate the alkylation and analyze the competition mechanism of phenolic compounds in mixture system. Finally, real lignin oil from depolymerized of beech powder was tested, and notably 80% of phenolic monomers in the oil were converted into fuel precursor. After hydrodeoxygenation, the alkylated product was converted to fuel blend with a density of 0.91 g/mL at 20 °C and a freezing point lower than −60 °C, very promising as high density fuel. This work provides a facile and energy-efficient way of synthesizing high-performance jet fuel directly from lignocellulosic derivatives, which decreases processing energy consumption and improve the utilization rate of feedstock.