The structure and stability of extended, inclined circumplanetary disc or ring systems

ABSTRACT Large dips in the brightness for a number of stars have been observed, for which the tentative explanation is occultation of the star by a transiting circumplanetary disc or ring system. In order for the circumplanetary disc/rings to block the host star’s light, the disc must be tilted out of the planet’s orbital plane, which poses stability problems due to the radial extent of the disc required to explain the brightness dip durations. This work uses N-body integrations to study the structure and stability of circumplanetary disc/ring systems tilted out of the planet’s orbital plane by the spinning planet’s mass quadrupole. Simulating the disc as a collection of test particles with orbits initialized near the Laplace surface (equilibrium between tidal force from host star and force from planet’s mass quadrupole), we find that many extended, inclined circumplanetary discs remain stable over the duration of the integrations ($\sim 3\!-\!16 \, {\rm Myr}$). Two dynamical resonances/instabilities excite the particle eccentricities and inclinations: the Lidov-Kozai effect which occurs in the disc’s outer regions, and ivection resonance which occurs in the disc’s inner regions. Our work places constraints on the maximum radial extent of inclined circumplanetary disc/ring systems, and shows that gaps present in circumplanetary discs do not necessarily imply the presence of exomoons.

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Stochasting modeling of planetary ring systems

International Astronomical Union Colloquium ◽

10.1017/s025292110010154x ◽

1984 ◽

Vol 75 ◽

pp. 461-469 ◽

Cited By ~ 1

Author(s):

Robert W. Hart

Keyword(s):

Maximum Entropy ◽

Ring System ◽

The Sun ◽

Ultimate State ◽

Interparticle Interactions ◽

Ring Systems ◽

First Order ◽

Planetary Ring ◽

Insight Into

ABSTRACTThis paper models maximum entropy configurations of idealized gravitational ring systems. Such configurations are of interest because systems generally evolve toward an ultimate state of maximum randomness. For simplicity, attention is confined to ultimate states for which interparticle interactions are no longer of first order importance. The planets, in their orbits about the sun, are one example of such a ring system. The extent to which the present approximation yields insight into ring systems such as Saturn's is explored briefly.

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Synthesis of Pyrazolofuropyrazine via One-Pot SNAr Reaction and Intramolecular Direct C–H Arylation

Synthesis ◽

10.1055/s-0036-1591885 ◽

2018 ◽

Vol 50 (07) ◽

pp. 1493-1498 ◽

Cited By ~ 3

Author(s):

Shinichiro Fuse ◽

Hiroyuki Nakamura ◽

Megumi Inaba ◽

Shinichi Sato ◽

Manjusha Joshi

Keyword(s):

Drug Discovery ◽

Rapid Development ◽

Ring System ◽

Biologically Active ◽

Drug Candidate ◽

One Pot ◽

Ring Systems ◽

Drug Candidates ◽

Fused Ring ◽

Snar Reaction

Fused-ring systems containing heterocycles are attractive templates for drug discovery. Biologically active 6-5-5+6 fused-ring systems that possess heterocycles are available, but these require a relatively large number of synthetic steps for preparation. Therefore, pyrazolofuropyrazine was designed as a 6-5-5+6 ring system template that incorporates ready accessibility for drug discovery. Pyrazolofuropyrazines were successfully constructed in only a few steps via one-pot SNAr reaction/intramolecular C–H direct arylation. As a drug candidate, pyrazolofuropyrazine has earned a favorable LogP, although significant biological activity has yet to be established; the ready accessibility of pyrazolofuropyrazine template, however, offers an opportunity for the rapid development of promising new drug candidates.

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The Meisenheimer Rearrangement in Heterocyclic Synthesis. IV. Derivatives of the 2H,6H-1,5,4-Benzodioxazocine and 7H-1,6,5-Benzodioxazonine Ring Systems: X-Ray Crystal Structure of 10-Methoxy-5-methyl-7-phenyl-2,3,4,5-tetrahydro-7H-1,6,5-benzodioxazonine

Australian Journal of Chemistry ◽

10.1071/ch9880293 ◽

1988 ◽

Vol 41 (3) ◽

pp. 293 ◽

Cited By ~ 11

Author(s):

JB Bremner ◽

EJ Browne ◽

LM Engelhardt ◽

IWK Gunawardana ◽

AH White

Keyword(s):

Molecular Structure ◽

Crystal Structure ◽

Crystal And Molecular Structure ◽

Ring System ◽

Heterocyclic Synthesis ◽

Rearrangement Product ◽

Ring Systems ◽

X Ray ◽

Derivatives Of ◽

Moderate Yield

Meisenheimer rearrangement of the N-oxides (4) derived from a series of 5-aryl-4-methyl-2,3,4,5-tetrahydro-1,4-benzoxazepines (3) gave rise to eight derivatives (5) of the new 2H,6H-1,5,4-benzodioxazocine ring system. Reaction of 9-methoxy-5-methyl-6-phenyl-3,4,5,6- tetrahydro-2H-1,5-benzoxazocine (6) with 3-chloroperoxybenzoic acid gave an unstable N-oxide (7). A Meisenheimer rearrangement product from (7), 10-methoxy-5-methyl-7-phenyl-2,3,4,5-tetrahydro-7 H-1,6,5- benzodioxazonine (8), the first example of this ring system, was isolated directly in moderate yield on oxidation of (6) with cooling. The crystal and molecular structure of (8) has been determined by X-ray crystallographic methods.

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Diastereoselective Total Synthesis of (±)-Schindilactone A, Part 1: Construction of the ABC and FGH Ring Systems and Initial Attempts to Construct the CDEF Ring System

Chemistry - An Asian Journal ◽

10.1002/asia.201200363 ◽

2012 ◽

Vol 7 (10) ◽

pp. 2321-2333 ◽

Cited By ~ 39

Author(s):

Tian-Wen Sun ◽

Wei-Wu Ren ◽

Qing Xiao ◽

Ye-Feng Tang ◽

Yan-Dong Zhang ◽

...

Keyword(s):

Total Synthesis ◽

Ring System ◽

Ring Systems

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On: “INVESTIGATION OF UPWARD CONTINUATION SYSTEMS” BY L. L. NETTLETON AND J. R. CANNON (GEOPHYSICS, DECEMBER, 1962, PP. 796–806)

Geophysics ◽

10.1190/1.1439254 ◽

1963 ◽

Vol 28 (4) ◽

pp. 669-670 ◽

Cited By ~ 1

Author(s):

Amalendu Roy

Keyword(s):

Ring System ◽

Ring Systems ◽

Upward Continuation ◽

Ideal Body

(1) Earlier tests of continuation systems on fields of ideal bodies minimized errors due to finite sizes of the ring systems used for calculation. This happened because the field due to an ideal body or a group of bodies falls to zero at large lateral distances. The object of Nettleton and Cannon’s paper is to correct this situation by conducting tests on “continuous” periodic fields. However, they seem to have largely defeated the purpose by choosing periodic fields which consist of alternations (about a zero value) of positive and negative anomalies of equal magnitude and the same (but inverted) shape. As long as the ring system is not unduly small, the contribution to the upward continuation integral from the area outside the ring system will be nearly zero. This is because the positive and the negative contributions from the plus and minus anomalies in such fields will tend to cancel each other. The fields chosen by Nettleton and Cannon, therefore, are virtually equivalent to what they themselves declared as unsatisfactory.

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Crystal structure of ethyl 1′,1′′-dimethyl-2′′,3-dioxo-3H-dispiro[benzo[b]thiophene-2,3′-pyrrolidine-2′,3′′-indoline]-4′-carboxylate

Acta Crystallographica Section E Crystallographic Communications ◽

10.1107/s2056989015002042 ◽

2015 ◽

Vol 71 (3) ◽

pp. o142-o142

Author(s):

M. P. Savithri ◽

M. Suresh ◽

R. Raghunathan ◽

R. Raja ◽

A. SubbiahPandi

Keyword(s):

Crystal Structure ◽

Hydrogen Bonds ◽

Title Compound ◽

Ring System ◽

Pyrrolidine Ring ◽

Ring Systems ◽

Envelope Conformation ◽

Compound C ◽

The Mean

In the title compound, C23H22N2O4S, the pyrrolidine ring has an envelope conformation with the spiro C atom, shared with the indoline ring system, as the flap. The mean planes of the benzothiophene and indoline ring systems are inclined to the mean plane of the pyrrolidine ring by 88.81 (8) and 79.48 (8)°, respectively, and to each other by 68.12 (5)°. In the crystal, molecules are linkedviaC—H...O hydrogen bonds, forming chains propagating along [001].

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N,N-Dialkyl-N'-Chlorosulfonyl Chloroformamidines in Heterocyclic Synthesis. Part VIII. Novel Pyrazolo-Fused Oxathiadiazines and Thiatriazoles

Australian Journal of Chemistry ◽

10.1071/ch09581 ◽

2010 ◽

Vol 63 (4) ◽

pp. 659 ◽

Cited By ~ 7

Author(s):

Craig M. Forsyth ◽

Craig L. Francis ◽

Saba Jahangiri ◽

Andris J. Liepa ◽

Michael V. Perkins ◽

...

Keyword(s):

Recent Work ◽

Major Product ◽

Ring System ◽

Heterocyclic Synthesis ◽

Ring Systems ◽

The Core ◽

Derivatives Of

N,N-dialkyl-N′-chlorosulfonyl chloroformamidines 1 reacted with pyrazol-3-ones 2 under a variety of conditions to give pyrazolo[2,3-e][1,2,3,5]oxathiadiazine dioxides 3 and pyrazolo[3,2-b][1,4,3,5]oxathiadiazine dioxides 5, and frequently, one or both of pyrazolo[1,2-b][1,2,3,5]thiatriazole 1,1,5-trioxides 4 and 1,1,7-trioxides 6. In all reactions, the pyrazolo[3,2-b][1,4,3,5]oxathiadiazine 5 was the major product, with the pyrazolo[2,3-e][1,2,3,5]oxathiadiazine 3 being a significant product in the absence of base. Prior to our recent work, the core ring systems of compounds 3 and 5 had not been reported and compounds 4 and 6 are new derivatives of a rare ring system.

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‘Ring Breaker’: Assessing Synthetic Accessibility of the Ring System Chemical Space

10.26434/chemrxiv.9938969.v1 ◽

2019 ◽

Author(s):

Amol Thakkar ◽

Nidhal Selmi ◽

Jean-Louis Reymond ◽

Ola Engkvist ◽

Esben Jannik Bjerrum

Keyword(s):

Chemical Space ◽

Ring System ◽

Ring Systems ◽

Multiple Reactions ◽

Zinc Database ◽

Synthetic Accessibility ◽

Synthesis Planning ◽

Reaction Graphs ◽

Synthetic Routes ◽

The Relationship

Ring systems in pharmaceuticals, agrochemicals and dyes are ubiquitous chemical motifs. Whilst the synthesis of common ring systems is well described, and novel ring systems can be readily computationally enumerated, the synthetic accessibility of unprecedented ring systems remains a challenge. ‘Ring Breaker’ enables the prediction of ring-forming reactions, for which we have demonstrated its utility on frequently found and unprecedented ring systems, in agreement with literature syntheses. We demonstrate its performance on a range of ring fragments from the ZINC database and highlight its potential for incorporation into computer aided synthesis planning tools. Additionally, we generate a multi-label dataset using bipartite reaction graphs on which we train ‘Ring Breaker’ to model the relationship between one ring fragment and the multiple reactions recorded for its synthesis in the dataset; we thereby overcome the single-label approaches previously used. These approaches to ring formation and retrosynthetic disconnection offer opportunities for chemists to explore and select more efficient syntheses/synthetic routes.

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4-(4-Bromophenyl)-2-(3-(4-chlorophenyl)-5-{3-[5-methyl-1-(4-methylphenyl)-1H-1,2,3-triazol-4-yl]-1-phenyl-1H-pyrazol-4-yl}-4,5-dihydro-1H-pyrazol-1-yl)-1,3-thiazole

IUCrData ◽

10.1107/s2414314618004431 ◽

2018 ◽

Vol 3 (3) ◽

Author(s):

Gamal A. El-Hiti ◽

Bakr F. Abdel-Wahab ◽

Rizk E. Khidre ◽

Mohamed S. Mostafa ◽

Amany S. Hegazy ◽

...

Keyword(s):

Title Compound ◽

Phenyl Ring ◽

Ring System ◽

Asymmetric Unit ◽

Ring Systems ◽

Axis Direction ◽

Compound C

The asymmetric unit of the title compound, C37H28BrClN8S, comprises one molecule. The molecule consists of two ring systems joined by a C—C bond between the dihydropyrazolyl and pyrazolyl rings of the two extended ring systems. The angles between adjacent ring planes of the tolyl–triazolyl–pyrazolyl–phenyl ring system are 48.2 (1), 12.3 (2) and 22.2 (2)°, respectively, with angles of 19.7 (1), 5.6 (2) and 0.9 (2)° between the rings of the chlorophenyl–thiazolyl–dihydropyrazolyl–bromophenyl set. The pyrazolyl and dihydropyrazolyl rings are inclined at 68.3 (1)° to one another. In the crystal, C—H...Cl interactions form chains of molecules parallel to theb-axis direction.

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‘Ring Breaker’: Neural Network Driven Synthesis Prediction of the Ring System Chemical Space

10.26434/chemrxiv.9938969.v3 ◽

2020 ◽

Author(s):

Amol Thakkar ◽

Nidhal Selmi ◽

Jean-Louis Reymond ◽

Ola Engkvist ◽

Esben Jannik Bjerrum

Keyword(s):

Neural Network ◽

Chemical Space ◽

Ring System ◽

Data Driven ◽

Ring Systems ◽

The Neural Network ◽

Synthetic Accessibility ◽

Synthesis Planning ◽

Data Driven Approach ◽

Synthetic Routes

Ring systems in pharmaceuticals, agrochemicals and dyes are ubiquitous chemical motifs. Whilst the synthesis of common ring systems is well described, and novel ring systems can be readily computationally enumerated, the synthetic accessibility of unprecedented ring systems remains a challenge. ‘Ring Breaker’ uses a data-driven approach to enable the prediction of ring-forming reactions, for which we have demonstrated its utility on frequently found and unprecedented ring systems, in agreement with literature syntheses. We demonstrate the performance of the neural network on a range of ring fragments from the ZINC and DrugBank databases and highlight its potential for incorporation into computer aided synthesis planning tools. These approaches to ring formation and retrosynthetic disconnection offer opportunities for chemists to explore and select more efficient syntheses/synthetic routes.

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