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The intermolecular cyclization of N-benzyl-2-cyanoacetamide with carbon disulfide followed by intramolecular cyclization gave thioxothiazinone 3. This compound was used to synthesize a series of novel fused furopyrrole, pyridine, pyrimidine and other azine and azole derivatives. The Michael-type reaction of compound 3 with maleic anhydride followed by pyrrole and furan cyclizations and aromatization yielded polycyclic compound 7. The [3+3]-cycloaddition of benzylidene malononitrile and its derivative to compound 3 gave pyridothiazines 10–12. The ring opening in compound 3 under the action of urea or thiourea followed by pyrimidine cyclization and subsequent air oxidation resulted in the synthesis of oxa- and thiadiazolopyrimidinones 15 and 16, respectively. The reaction of compound 3 with H2O2 in a basic medium provided pyrimidine derivative 17. The oxidation of compound 3 with Br2 in an acid medium led to bromo derivative 19. The synthesized novel compounds were characterized by elemental analysis and IR and 1H and 13C NMR spectroscopy and tested antibacterial and anticancer activities.

A silver‐triggered heterogeneous Pd‐catalyzed oxidative carbonylation has been developed. This heterogeneous process exhibits high efficiency and good recyclability, and was utilized for the one‐pot construction of polycyclic compounds with multiple chiral centers. AgOTf was used to remove chloride ions in the heterogeneous catalyst Pd‐AmP‐CNC, thereby generating highly active PdII, which results in high efficiency of the heterogeneous catalytic system., Silver bullet: A silver‐triggered heterogeneous palladium‐catalyzed oxidative carbonylation of allene amides was developed for the one‐pot construction of pyrrolidones and polycyclic compounds with multiple chiral centers. The heterogeneous catalyst (Pd‐AmP‐CNC) can be recycled at least nine times without loss of activity. The Ag salt removes Cl from Pd‐AmP‐CNC to generate highly active PdII, which results in high efficiency of the heterogeneous catalytic system.

Polypropylene (PP) has great potential to be used as recyclable high-voltage direct current (HVDC) cable insulation material. Electrical tree is the key factor that leads to cable insulation failure and limits the increase of HVDC transmission voltage level. In this study, three different polycyclic compounds, namely 4,4'-bis(dimethylamino)phenylazo, 2-hydroxy-2-phenylacetophenone and 4-phenylbenzophenone, are added into PP matrix with the addition content of 0.1 wt%. The electrical treeing experiments are conducted under impulse superimposed DC voltage at 30, 70 and 90 °C. Then the polycyclic compound with the best effect on inhibiting electrical tree is selected, and its filling ratio is further changed from 0.1 wt% to 0.3 wt% to get the optimal inhibition effect. It is found that the addition of 2-hydroxy-2-phenylacetophenone can inhibit the electrical tree degradation. However, the addition of 4-phenylbenzophenone and 4,4'-bis(dimethylamino)benzene will increase the electrical tree length and accumulated damage. As the content of 2-hydroxy-2-phenylacetophenone increases, the electrical tree length and accumulated damage decrease firstly, and then increase. The effect of polycyclic compounds on the electrical tree degradation is affected by the relative polarity of impulse superimposed DC voltage and temperature. The experimental results reveal that adding 0.1 wt% 2-hydroxy-2-phenylacetophenone polycyclic compound to PP can effectively inhibit the electrical tree degradation, which has great potential for application in recycle HVDC cables.

In this chapter, the electric ageing and breakdown phenomenon of polypropylene (PP) under impulse superimposed DC voltage was studied first. Then three different polycyclic compounds were added to PP, namely 4,4′-bis(dimethylamino)benzil, 2-hydroxy-2-phenylacetophenon and 4-phenylbenzophenone. The electrical tree aging experiments were carried out on these samples at 30, 60 and 90 °C under impulse superimposed DC voltage. The effect was compared and the polycyclic compound that inhibited the electrical tree best was selected, and then the addition amount of the polycyclic compound was changed from 0.1 to 0.3 wt.% to get the best inhibition effect. The results show that under impulse superimposed DC voltage, different DC amplitude, pulse amplitude and pulse frequency have an effect on electric ageing and breakdown phenomenon. 2-hydroxy-2-phenylacetophenon can inhibit the growth of electrical tree. However, 4,4′-bis(dimethylamino)benzil and 4-phenylbenzophenone promote electric ageing and breakdown. Adding 0.1 wt.% of 2-hydroxy-2-phenylacetophenon polycyclic compound to PP can effectively inhibit the growth of electrical tree and inhibit electric ageing and breakdown phenomenon. It is a potential environmental friendly type HVDC cable insulation material.

We report on the preparation and characterization of a thiazole-fused polycyclic compound containing an s-indacene chromophore, which has the characteristics of an antiaromatic system. X-ray analys...

Aromatic compounds are well-known due to their stability, and this efficiently provides several applications. However, this does not indicate low reactivity for every condition. For instance, electrophilic substitution reactions are widespread and easily performed. Otherwise, reactions that induce the loss of aromaticity, such as condensed cyclizations are uncommon. These last types of reactions typically occur under severe conditions, under heat influx and high pressure. Here we report the formation of a dihydrochloride salt monohydrate of an ionic polycyclic compound bearing a four fused six-membered rings motif. This complex compound was obtained by the simple reaction of 2-aminopyrazine with hydrochloric acid in an aqueous medium at room temperature. Crystal data and DFT calculations could confirm the cyclocondensation of 2-aminopyrazine.

A macrocyclic polyketide with novel carbon skeleton, namely hainanmycin A, was isolated from the mangrove-derived Streptomyces sp. 219807. This polycyclic compound featured a cyclo-heptadeca framework possessing a 5,6-disubstituted-4-hydroxy-2-pyrone moiety in conjunction with a 2-cyclopentenone residue. The structure was established by spectroscopic analyses, and the stereochemistry was determined by NMR chemical shifts calculations and time-dependent density functional theory (TDDFT) calculation of electronic circulardichroism (ECD). A possible biogenetic pathway for hainanmycin A was proposed.

An efficient and simple synthesis of novel trisubstituted 1H-pyrroles 4a–qvia 1,3-dipolar cycloaddition of Δ3-trifluoromethyloxazolones 2a–d with both chromium and tungsten alkynyl Fischer carbene complexes (1a–h) is described. An unexpected and unreported –CF3 group elimination process was observed in the pyrrole structure. Our experimental and theoretical data suggested that the metal fragment may be responsible for this phenomenon. The dipolar cycloaddition proceeded efficiently to produce a single regioisomer, which was unambiguously established through NMR and single-crystal X-ray diffraction studies. Nevertheless, the reaction of alkynyl carbenes bearing an α,β,γ,δ-unsaturated moiety with excess oxazolone 2a produced a polycyclic compound 6 speculatively formed through a cascade reaction involving 1,6-, 1,4- and 1,2-nucleophilic addition steps.

Electrical tree is an important factor in the threat of the safety of cross-linked polyethylene (XLPE) insulation, eventually leading to the electrical failure of cables. Polycyclic compounds have the potential to suppress electrical treeing growth. In this paper, three types of polycyclic compounds, 2-hydroxy-2-phenylacetophenone, 4-phenylbenzophenone, and 4,4&prime, difluorobenzophenone are added into XLPE, denoted by A, B, and C. Electrical treeing characteristics are researched with DC-impulse voltage at 30, 60, and 90 &deg, C, and the trap distribution and carrier mobility are characterized. It has been found that although three types of polycyclic compounds can all suppress the electrical tree propagation at different voltages and temperatures, the suppression effect of these polycyclic compounds with the same DC-impulse polarity is worse than with the opposite polarity. As the temperature increases, the suppression effect becomes weak. The energy level and deep trap density are the largest in XLPE-A composite, leading to a decrease in the charge transportation and resulting in the suppression of electrical treeing growth. Experimental results reveal that the polycyclic compound A has great application prospects in high voltage direct current (HVDC) cables.

Fused coumarins recently attracted strong scientific interest due to their potent pharmacological activities. In this study, density functional theory (DFT) calculations were performed to evaluate the antiradical activities of a series of coumarin-fused coumarins. By calculating the thermodynamic parameters, three primary mechanisms including hydrogen atom transfer (HAT), electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET) were examined. It was found that in the gas and benzene phases, the studied compounds prefer to undergo HAT mechanism, while SPLET is more favored in polar media. The results also reveal the possibility of double HAT and double SPLET mechanisms for compound CC-6. Interestingly, a new polycyclic compound was generated by forming a new C5-O5' bond during the second HAT process at the 5'-OH in CC-6-R6 radical. In addition, the SPLHAT mechanism is proposed as a competitive pathway for radical scavenging by CC-4, CC-5 and CC-6.

1-Aryl-β-carboline-3-carbaldehyde building blocks have been used as the starting materials for the synthesis of novel bis-β-carboline derivatives. In the two-step synthesis the Pictet–Spengler reaction was used before the dehydrogenation of the polycyclic compound to the aromatic derivatives.

Efficient methods for the convergent synthesis of (poly) cyclic scaffolds are urgently needed in synthetic and medicinal chemistry. Herein, we describe new annulation reactions of thioalkynes with phthalimide-substituted donor-acceptor cyclopropanes, which gave access to highly substituted cyclopentenes and polycyclic ring systems. With silyl-thioalkynes, the Lewis acid catalyzed[3+2] annulation reaction with donor-acceptor cyclopropanes took place to afford 1-thio-cyclopenten-3-amines. On the other hand, an unprecedented polycyclic compound was formed with alkyl-thioalkynes through a reaction pathway directly involving the phthalimide group. The two transformations proceeded in good yields and tolerated a large variety of functional groups.

Current healthcare has significantly increased the average life expectancy, leading to a consequently greater incidence of age-related diseases, such as Alzheimer's disease. Following a multitarget approach, in this paper a series of polycyclic maleimide-based derivatives were designed and synthesized aimed at simultaneously modulate neuronal calcium channels and glycogen synthase kinase 3-beta (GSK-3β), validated targets to combat Alzheimer’ disease. Different structural modifications were performed on the polycyclic scaffold in order to investigate the structure-activity relationships and compound 10 emerged as a promising non-toxic lead compound, endowed with calcium modulating brain-addressed properties and significant GSK-3β inhibitory activity. Moreover, the easily affordable polycyclic core appears as a new appealing privileged structure in medicinal chemistry.

Treatment of tetrakis(dimethylamino)diboron (B₂(NMe₂)₄) with 1,4-bis (2-(triisopropylsilyl)ethynyl)naphthalene-2,3-diamine (1) generated a large NBBN polycyclic compound 1,1-B₂{2,3-(NH)₂ -1,4-(ⁱPr₃ SiC₂)₂C₁₀H₄} (2). The X-ray structure analysis reveals that 2 has a twisted structure (dihedral angle ≈ 21.75°) with a rather short B-B bond (1.667(9) Å). Theoretical calculations on 1,1-B₂ isomer 2 and its counterpart 1,2-B₂ isomer 3 have been conducted to understand their frontier orbital energy levels. Compound 2 shows strong emission with a high quantum yield of 0.52, despite the presence of many unbeneficial non-radiative behaviors such as the vibration of the TIPS groups and the rotation of the B-B single bond.

New cyclopentene-fused octahydropyridoquinolines and octahydrophenanthrolines were prepared by a stereoselective three-component cyclocondensation of benzene-1,4-diamine, cyclopenta-1,3-diene, and an aromatic aldehyde. Single-crystal X-ray diffraction data provided evidence for the formation of cyclopentene-fused octahydropyridoquinolines and octahydrophenanthrolines with a syn -planar arrangement of the cyclopentene rings. The cyclocondensation of benzene-1,4-diamine, cyclopenta-1,3-diene, and formaldehyde gave new type of polycyclic compound containing four cyclopentene moieties oriented in a mutually antiplanar manner.

An analytical pyrolysis gas chromatography mass spectrometry method has been used for investigation into the reaction mechanism leading to polycyclic compounds such as polycyclic aromatic hydrocarbons and heterocyclic compounds. Six phenols with different pendant groups were used in this study. The formation mechanism of producing naphthalene and dibenzofuran from phenol is proposed. In this mechanism, a cyclohexadiene-1-one radical was an important intermediate for the formation of these products. Three unique products were detected from m-cresol: 3,7-dimethyldibenzofuran, 1,7-dimethyldibenzofuran and 1,9-dimehyldibenzofuran. Cyclohexadiene-1-one radical was also found to be an important intermediate for dimerization reaction. Guaiacol pyrolysis yielded phenol as the major product, with a small amount of benzofuran. There arrangement of methoxyl group to methyl group and addition of methyl radical on phenoxy radical was a crucial route in this mechanism. From pyrocatechol, three indanone derivatives were produced via CO elimination with aromatic ring opening followed by pentadienone formation. After two proton donation, three pentanone biradicals were intra molecularly coupled to form indanones. From syringol pyrolysis, only benzofuran was produced, and from ethyl phenol, three types of benzofuran were detected containing different pendant groups such as methyl, ethyl and ethenyl groups. These results indicated that the phenol’s ortho position is a vital reaction site for the formation of polycyclic compounds in pyrolysis.

A Rh-catalyzed intermolecular [2 + 2 + 2] cycloaddition of the 2,3-double bond of benzothiophene dioxides with α,ω-diynes gave sulfone-containing cycloadducts in high yields. This is the first example of a catalytic [2 + 2 + 2] cycloaddition that uses the 2,3-double bond of a heterole as an ene moiety. The consecutive reaction of benzodithiophene tetraoxide with 2,3-naphthylene-tethered 1,7-diyne gave an 11-ring condensed polycyclic compound in one pot.

A straightforward synthesis of ecteinascidin 743 was accomplished from readily available l-glutamic acid as a single chiral source. Our novel synthesis features a concise and convergent approach for construction of the B-ring, consisting of a sequence involving a stereoselective Heck reaction between a diazonium salt and an enamide, oxidative cleavage of the resulting alkene, and intramolecular ortho substitution of the phenol by an aldehyde.

Mono- and dianions of a polycyclic compound with a central sp3-hybridized silicon atom, spirosilabifluorene (C24H16Si, 1), were prepared by reduction with alkali metals. The salts containing 1•– and 12– anions were isolated and studied by single-crystal X-ray diffraction. The lithium salt of the C24H16Si•– radical monoanion ([Li(THF)4+][1•–], 2) exists as a solvent-separated ion pair in the solid state. Substantially different geometrical parameters were found for each of the fluorene groups within the C24H16Si•– anion of 2 due to asymmetric charge distribution. The C24H16Si2– dianion was isolated in the form of its sodium ([{Na(THF)3+}{Na(THF)+(12–)], 3) or potassium ([{K(THF)+}2(12–)], 4) salt. The environment at the central silicon atom in the dianion is flattened in comparison to the monoanion and neutral compound, with the angle between the two fluorene planes measured at 55° in 12– vs 89° in 1•– and 83° in 10. The aggregation of dianions and alkali-metal counterions leads to the formation of dimeric...

The total synthesis of naphthoquinone natural products isolated from the Bignoniaceae plant family is described. Pinnatal, isopinnatal, sterekunthals A and B, pyranokunthones A and B, and anthrakunthone have been prepared along the lines of a biosynthetic proposal involving pericyclic reactions as key steps. The first case of catalysis in oxa 6pi electrocyclizations is reported.

The century-old Zincke process for ring-opening of pyridinium salts produces 5-amino-2,4-pentadienals, a type of donor-acceptor dienes known as Zincke aldehydes. Inspired by this reasonably general and often efficient process for dearomatization, my laboratory has used pyridines as a starting point for heterocycle synthesis, which resulted in unusual syntheses of indoles, pyrrolines, and a formal synthesis of the natural product porothramycin A. Furthermore, our study of the reactivity of Zincke aldehydes has led to accidental discoveries of pericyclic cascade reactions that produce Z-α,β-unsaturated amides or polycyclic lactams, depending upon the identity of the substituents on nitrogen. Finally, a base-mediated formal cycloaddition reaction of tryptamine-derived Zincke aldehydes has served as the key step in concise syntheses of the indole alkaloids norfluorocurarine and strychnine.

In an approach directed toward a tashironin based complex natural product, efficacy of the singlet oxygen mediated [4+2]-cycloaddition to a tetracyclic cyclopentadiene has been evaluated to install the key cis-1,4-dihydroxy functionality. (C) 2011 Elsevier Ltd. All rights reserved.

An attempted synthesis of the angularly annelated 9-(11'-benzo[a]fluoren-11'-ylidene)-9H-fluorene (3) through a Peterson olefination reaction between (9H-fluoren-9-yl)trimethylsilyl anion (5a) and 11H-benzo[a]fluoren-11-one (6) led to the linearly annelated 9-(11'-benzo[b]fluoren-11'-ylidene)-9H-fluorene (4), due to an unexpected rearrangement. The proposed mechanism of the rearrangement is illustrated. The core of the mechanism is an intramolecular Haller-Bauer cleavage of the naphthyl C 11a' -C 11' bond in the β-oxysilane anion 11 (formed from 5a and 6) to give the 1-naphthyl anion (E)-12, followed by E/Z isomerization to (Z)-12 and by proton migration to give the 3-naphthyl anion (Z)-14. The intramolecular nucleophilic addition of the naphthyl anion at C-3' of (Z)-14 to the carbonyl carbon gives the β-oxysilane anion 15, a benzo[b]fluorenylidene derivative. The mechanism is supported by the results of DFT calculations. The synthesis of 3 was achieved by application of Barton's double extrusion diazo-thione coupling method.

A protocol for the synthesis of the fused heterocyclic polycyclic compounds pyrrole[1,2-a]benzimidazoles, piperidine[1,2-a]benzimidazoles and oxa-fused benzimidazoles using iodine and silver nitrate by an exo-dig or endo-dig cyclization pathway at room temperature has been developed. Silver nitrate is a key additive for improving the yield, and the improvement is a result of this additive eliminating the influence of iodine ions (I ― ), which would otherwise lead to the formation of bis-iodine by-products. Cyclizations involving terminal and substituted alkynes were performed. Further functionalizations demonstrated that the iodo derivatives obtained are potential synthetic intermediates that can increase the molecular complexity.

A variety of dioxa[4.3.3]propellanes are efficiently obtained starting from a dehydrotetramer of 2,4-dimethylphenol. The final installation of the phenol component requires a domino sequence based on electrophilic substitution and a ketalization process. The molecular structure of these dioxa[4.3.3]propellanes was elucidated by 2D NMR techniques as well as X-ray analysis of suitable single crystals. Most of these polycyclic products were formed with high regio- and diastereoselectivity.

Two new triptycene-containing bis(ether amine)s, 1,4-bis(4-aminophenoxy)triptycene (4) and 1,4-bis(4-amino-2-trifluoromethylphenoxy)triptycene (6), were synthesized, respectively, from the nucleophilic chloro-displacement reactions of p-chloronitrobenzene and 2-chloro-5-nitrobenzotrifluoride with 1,4-dihydroxytriptycene in the presence of potassium carbonate, followed by palladium-catalyzed hydrazine reduction of the dinitro intermediates. The bis(ether amine)s were polymerized with six commercially available aromatic tetracarboxylic dianhydrides to obtain two series of novel triptycene-based polyimides 8a―f and 9a―f by using a conventional two-step synthetic method via thermal and chemical imidizations. All the resulting polyimides exhibited high enough molecular weights to permit the casting of flexible and strong films with good mechanical properties. Incorporation of trifluoromethyl groups in the polyimide backbones improves their solubility and decreases their dielectric constants. The fluorinated polyimides 9d and 9f derived from diamine 6 with 4,4'-oxydiphthalic anhydride and 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), respectively, could afford almost colorless thin films.

An organocatalytic tandem Michael-Michael reaction is developed for the simple preparation of stereo complex, polycyclic compounds from simple reactants in satisfactory yields (up to 90%) and excellent diastereoselectivities (>30:1 dr).

Processes that form multiple carbon-carbon bonds in one operation can generate molecular complexity quickly and therefore be used to shorten syntheses of desirable molecules. We selected the hetero-Pauson-Khand (HPK) cycloaddition and ring-closing metathesis (RCM) as two unique carbon-carbon bond-forming reactions that could be united in a tandem ruthenium-catalyzed process. In doing so, complex polycyclic products can be obtained in one reaction vessel from acyclic precursors using a single ruthenium additive that can catalyze sequentially two mechanistically distinct transformations.

The first synthesis ofpyrido[3,2-b]carbazole as an ellipticine―makaluvamine hybrid in 13 steps and 2% overall yield from commercially available 2,5-dimethoxyaniline is described.