Bicyclic Products Research Articles

Templated Assembly of Chiral Medium-Sized Cyclic Ethers via 8-endo-trig Nucleophilic Cyclization of Cyclopropenes.

An efficient approach toward enantioenriched eight-membered heterocycles via the intramolecular formal substitution of bromocyclopropanes with oxygen-based nucleophiles has been developed. The reaction proceeds via a reactive cyclopropene intermediate, which undergoes a rapid 8-endo-trig cyclization affording cis-fused [6.1.0] bicyclic products exclusively. The quaternary chiral center in the cyclopropene governs the configuration of the other two stereocenters in the final product.

Study of Cascade Ring-Closing Metathesis Reactions en Route to an Advanced Intermediate of Taxol.

A highly functionalized intermediate in the synthesis of Taxol has been synthesized, which features the tricyclic core and the required oxygen substituents at C1, C2, C7, C10, and C13. The key step, a ring-closing dienyne metathesis (RCDEYM) reaction, has been thoroughly optimized to favor the tricyclic product over the undesired bicyclic product resulting from diene metathesis.

Enhanced recycling network for spent e-bicycle batteries: A case study in Xuzhou, China

Electric bicycles (e-bicycles) are a primary means of commuting in China because of their light weight, speed, and low maintenance costs. Owing to short service life and environmental pollution hazards, recycling and reuse of e-bicycle batteries has always been a focus of industry and academia. As a typical case of both production and use of large electric bicycles, 113 major sellers, 378 corporate and individual buyers, 147 large e-bicycle repair centers, and 1317 e-bicycle owners in Xuzhou City were investigated in order to understand the sales, use, recycling, and disposal of spent e-bicycle batteries. The findings show that the existing distempered recycling system is the main limitation of spent battery recovery, and the actual recovery rate of spent batteries is lower than the estimated output (QW) for the years 2011–2014. Electric bicycle sellers play a fundamental role in the collection of spent batteries in Xuzhou, accounting for 42.3±8.3% of all batteries recovered. The widespread use of lithium batteries in recent years has resulted in a reduction in spent battery recycling because of lower battery prices. Furthermore, consumer preferences are another important factor affecting the actual recovery rate according to survey results evaluated using canonical correspondence analysis. In this paper, we suggest that a reverse logistics network system for spent battery recycling should be established in the future; in addition, enhancing producer responsibility, increasing publicity, raising of public awareness, developing green public transport, and reducing dependence on e-bicycles also should be pursued. This study seeks to provide guidance for planning construction and management policies for an effective spent battery recycling system in China and other developing countries.

New Regio- and Stereoselective Cascades via Unstabilized Azomethine Ylide Cycloadditions for the Synthesis of Highly Substituted Tropane and Indolizidine Frameworks.

Multisubstituted tropanes and indolizidines have been prepared with high regio- and stereoselectivity by the [3+2] cycloaddition of unstabilized azomethine ylides generated from readily prepared trimethylsilyl-substituted 1,2-dihydropyridines via protonation or alkylation followed by desilylation. Starting from 1,2-dihydropyridines bearing a ring trimethylsilyl substituent at the 6-position, an intermolecular alkylation/desilylation provides endocyclic unstabilized ylides that successfully undergo cycloaddition with a range of symmetrical and unsymmetrical alkyne and alkene dipolarophiles to afford densely substituted tropanes incorporating quaternary carbons in good yields and with high regio- and stereoselectivity. Additionally, an intramolecular alkylation/desilylation/cycloaddition sequence provides convenient and rapid entry to bridged tricyclic tropane skeletons, allowing for five contiguous carbon stereocenters to be set in a single experimental operation and under mild conditions. Starting from 1,2-dihydropyridines with trimethylsilylmethyl groups on nitrogen, protonation followed by desilylation generates exocyclic unstabilized ylides that undergo cycloaddition with unsymmetrical alkynes to give indolizidines with good regio- and stereoselectivity. N-Trimethylsilylmethyl-1,2-dihydropyridines can also be alkylated and subsequently desilylated to give endocyclic unstabilized ylides that undergo intermolecular cycloadditions with carbonyl compounds to give bicyclic oxazolidine products in good overall yields. Moreover, an intramolecular alkylation/desilylation/cycloaddition sequence with the N-trimethylsilylmethyl-1,2-dihydropyridines affords tricyclic indolizidines that incorporate quaternary carbons and up to five stereocenters with good to excellent regio- and diastereoselectivity.

Effective Chirality Transfer in [3+2] Reaction between Allenyl-Rhodium and Enal: Mechanistic Study Based on DFT Calculations.

Theoretical calculation was performed to study the chirality transfer in a newly reported intramolecular [3+2] cycloaddition of enal and alleno rhodium species, generated in situ from an enynol precursor. [3.3.0] bicyclic system which contains two bridgehead quaternary carbons that can be achieved, the chirality of which are controlled by those of the starting material, and the product stereoselectivity is only determined by the α-position of the acetylene moiety. Density functional theory calculations predicted that only the cis [3.3.0] bicyclic product could be generated, regardless of either erythro or threo substrate, which was also confirmed by experimental observations.

ChemInform Abstract: Synthesis of Cyclic Guanidines via Silver‐Catalyzed Intramolecular Alkene Hydroamination Reactions of N‐Allylguanidines.

The silver-catalyzed hydroamination of tosyl-protected N-allylguanidines is described. These reactions provide substituted cyclic guanidines in high yields. The reactions are amenable to the construction of quaternary stereocenters as well as both monocyclic and bicyclic guanidine products.

ChemInform Abstract: Templated Assembly of Medium Cyclic Ethers via exo‐trig Nucleophilic Cyclization of Cyclopropenes.

A novel method for the assembly of medium heterocycles via an intramolecular nucleophilic addition to cyclopropenes generated in situ from the corresponding bromocyclopropanes is described. The exo-trig nucleophilic cyclizations were shown to proceed very efficiently and in a highly diastereoselective fashion affording cis-fused bicyclic products possessing 7 to 10-membered medium rings; starting from a diastereomeric mixtures of bromocyclopropanes.

Design and Implementation for Ontology Modeling of Design Knowledge Based on UML Class Diagram

With the research and development of knowledge management in product design, OWL models and other semantic languages have some problems such as the fuzziness hierarchy, lake of the representation of visualization model, so the modeling of semantic web maybe become the main bottleneck. Now it has become important research direction that applying UML which is the concept modeling language into the modeling of semantic web. This paper proposes the knowledge management model in product design through the UML class diagram. By using the UML modeling method and object-oriented technology the knowledge-oriented task structure model of product design was established though the task structure of product design. And the knowledge-oriented component structure model of product design was established though the component structure of product design and object-oriented design knowledge of design feature. At last, through the simulation of design knowledge ontology that was established and tested for the bicycle product, it shows that using this method can build ontology modeling directly and clearly which also can reduce the complexity of establishment and maintenance of large-scale ontology model, and lay a good foundation for the future research about developing more mature semantic soft.

A Modular Four-Component Route to Substituted 1,7,9-Decatrien-3-ones Using a Chloro-Substituted Phosphorane as Key C3 Building Block

An efficient and flexible four-component route to substituted 1,7,9-decatrien-3-ones was established by alkylation of sodium dialkyl malonates with a chloro-substituted phosphorane followed by a Wittig reaction with the corresponding carbonyl compound. The resulting enones were alkylated at their malonate unit with sorbyl bromide to give the title compounds in good overall yields. In an attempt to improve the overall yield by using in situ generated sorbyl tosylate we discovered the formation of an unusual bicyclic product with a 3-oxocyclopenta[b]furan core that is formally generated by an oxidative dimerization of the employed precursor enone. The structure of this compound was unambiguously determined by an X-ray crystal analysis.

Synthesis of Cyclic Guanidines via Silver-Catalyzed Intramolecular Alkene Hydroamination Reactions of N-Allylguanidines.

The silver-catalyzed hydroamination of tosyl-protected N-allylguanidines is described. These reactions provide substituted cyclic guanidines in high yields. The reactions are amenable to the construction of quaternary stereocenters as well as both monocyclic and bicyclic guanidine products.

Discovery and Development of a Three-Component Oxidopyrylium [5 + 2] Cycloaddition.

α-Hydroxy-γ-pyrone-based oxidopyrylium cycloaddition reactions are useful methods for accessing a highly diverse range of oxabicyclo[3.2.1]octane products. Intermolecular variants of the reaction require the formation of a methyl triflate-based pre-ylide salt that upon treatment with base in the presence of alkenes or alkynes leads to α-methoxyenone-containing bicyclic products. Herein, we describe our discovery that the use of ethanol-stabilized chloroform as solvent leads to the generation of α-ethoxyenone-containing bicyclic byproducts. This three-component process was further optimized by gently heating a mixture of a purified version of the oxidopyrylium dimer in the presence of an alcohol prior to addition of a dipolarophile. Using this convenient procedure, several new oxidopyrylium cycloaddition products can be generated in moderate yields. We also highlight the method in a tandem ring-opening/debenzylation method for the generation of α-hydroxytropolones.

Hydrogenolysis/hydrogenation of diphenyl ether as a model decomposition reaction of lignin from biomass in pressurized CO2/water condition

Catalytic hydrogenolysis of the CO bond of diphenyl ether (a lignin model compound) was investigated as a function of hydrogen pressure in scCO2 medium in the presence of water. Using commercially available Rh/C catalyst, the CO bond cleavage of diphenyl ether mainly results phenolic monomer at 80°C. Hydrogen pressure is one of the key parameters because (i) CO bond cleavage and the hydrogenation of aromatic rings are two competitive reactions; very sensitive to hydrogen pressure and (ii) hydrogen has complete solubility in scCO2. Therefore, a critical control of hydrogen pressure was essential to reach the targeted cleavage of the CO bond when the reaction was conducted in scCO2 medium under pressurized condition. Depending on the hydrogen pressure, a significant change in the ratio of monocyclic:bicyclic products from 91:9 (0.2MPa) to 58:42 (2MPa) was revealed in the shortest reaction time of 5min. Thus, low hydrogen pressure was the effective choice for the scission of the CO bond, whereas higher hydrogen pressure hydrogenate the aromatic ring due to the higher coverage of hydrogen on the catalytic surface. Amount of the catalyst (catalyst:substrate ratio) displayed a subtle effect on the breakage of the CO bond. A threshold ratio of 1:5 was preferred under the present reaction condition as the increased amount hampered the substrate:water ratio and hydrogenation of the aromatic ring occurred. In addition, as the change in temperature is associated with the change in the physical properties of scCO2, hence, the effect on the transformation of DPE was complicated and difficult to explain. Furthermore, different organic solvents as neat, along with CO2 and with water also has substantial impact on the rapture of CO bond. The obtained results from the solvent studies again proved that scCO2 along with water was the best choice for CO bond breakage and water is the driving force to mediate the reaction. In addition, a combination catalyst (Ni+Rh) was also tested for the same reaction under the similar working condition. Preliminary results suggested a synergistic effect in terms of the selectivity of monocyclic compounds.

Synthesis of functionalized 2,3-dihydropyrroles by oxidative radical cyclization of N-Sulfonyl β-enamino esters with alkenes

Oxidative radical cyclization of N-sulfonyl β-enamino esters with alkenes has been developed. Substituted 2,3-dihydropyrroles were produced when the reactions were carried out in the presence of CAN and Cu(OAc)2 as the oxidant. Intramolecular cyclization of β-enamino carbonyl compounds having an alkenyl and an alkynyl side chain proceeded to afford the corresponding bicyclic products, respectively.

ChemInform Abstract: Enantioselective Organocatalytic Michael Addition—Cyclization Cascade of Cyclopentane‐1,2‐dione with Substituted (E)‐2‐Oxobut‐3‐enoates.

AbstractStarting from cyclopentane‐1,2‐dione and aryl substituted (E)‐2‐oxobut‐3‐enoates bicyclic hemiacetal products with two stereogenic centres are formed in high yields and with very high enantiomeric purity.

An integrated model for strategic supply chain design: Formulation and ABC-based solution approach

This study develops a mixed integer nonlinear programming (MINLP) model to design supply chains. In view of the limitations of many available strategic supply chain design models, this model involves three major supply chain stages, including procurement, production, and distribution, and their interactions; it takes into account bill of materials constraints for modeling complex supply chain inter-relationships. In addition, in accordance with the fact that companies nowadays develop product families, our model addresses multi-product supply chain design to respond to diverse customer requirements. Recognizing their importance, this study identifies and formulates constraints related to facility pairwise relationships and supplier priority along with the classical constraints from the available literature. To efficiently solve such a highly constrained, large scale MINLP model, we develop an approach based on an artificial bee colony (ABC) algorithm. Bicycle design and production is used to demonstrate the potential of the MINLP model for designing supply chains and the performance of the ABC-based solution approach in solving the model. The proposed model and solution approach can be considered as two fundamental components of an expert system in the broad sense. Thus, this study is expected to stimulate more future research on the development of practical expert systems for designing supply chains.

Templated assembly of medium cyclic ethers via exo-trig nucleophilic cyclization of cyclopropenes

A novel method for the assembly of medium heterocycles via an intramolecular nucleophilic addition to cyclopropenes generated in situ from the corresponding bromocyclopropanes is described. The exo-trig nucleophilic cyclizations were shown to proceed very efficiently and in a highly diastereoselective fashion affording cis-fused bicyclic products possessing 7 to 10-membered medium rings; starting from a diastereomeric mixtures of bromocyclopropanes.

ChemInform Abstract: Synthesis of 6‐Aryl‐4H‐imidazo[1,2‐b][1,2,4]triazoles and 6‐Aryl‐thiazolo[3,2‐b][1,2,4]triazoles.

AbstractSome of the bicyclic products exhibit antibacterial activity.

ChemInform Abstract: Studies on the Reaction of Aryl Glyoxals with‐Prolinol: Unexpected Formation of Morpholin‐2‐one Derivatives and Stereoselective Trifluoromethylation of the Bicyclic System.

AbstractThe reaction of L‐prolinol with aryl glyoxals affords labile bicyclic products (III), which undergo isomerization in the presence of an acid to form morpholine derivatives as single diastereomer (IV) or mixtures of diastereomers (VII).

The molecular composition of Sicilian amber

In this study for the first time the bulk chemical composition of Sicilian amber (simetite) was determined using pyrolysis–gas chromatography–mass spectrometry with thermally assisted hydrolysis and methylation (Py(THM)–GC–MS). The results evidenced that the polymer fraction of Sicilian amber is based on a polylabdanoid structure with an enantio configuration, mainly including ozic acid and biformene. In addition, numerous monocyclic and bicyclic terpene degradation products could be detected. At higher retention times several characteristic compounds were found. Very low amounts of succinic acid could be revealed. The chemical data allowed to classify simetite as a Class 1c resinite and to suggest a botanical origin from Fabaceae.

Regiochemical and Stereochemical Studies of the Intramolecular Dipolar Cycloaddition of Nitrones Derived from Quaternary Aldehydes

Three aldehydes each with a quaternary α-carbon stereocentre bearing an alkenyl, a phenyl, and a methyl ester group were treated with N-methylhydroxylamine. In each case bicyclic isoxazolidine products were formed by condensation to give intermediate nitrones that undergo intramolecular dipolar cycloaddition. The stereoselectivity was influenced by the α-carbonyl substituent, possibly by a hydrogen bond between CO and a nearby CH of the nitrone in the transition state (supported by DFT and X-ray studies), and the regioselectivity was affected by the length of the tether and by the presence of an ester on the alkene dipolarophile.