Six-Membered Cyclic Nitroso Acetals: Synthesis and Studies of the Nitrogen Inversion Process ofN-Silyloxy-3,6-dihydro-2H-1,2-oxazines

2016 ◽  
Vol 2016 (33) ◽  
pp. 5569-5578 ◽  
Author(s):  
Alexander S. Shved ◽  
Andrey A. Tabolin ◽  
Roman A. Novikov ◽  
Yulia V. Nelyubina ◽  
Vladimir P. Timofeev ◽  
...  
Keyword(s):  
Inversion Process ◽  
Nitrogen Inversion

scholarly journals A study of nitrogen inversion process in some camphor-based isoxazolidines

ARKIVOC ◽  
2008 ◽  
Vol 2008 (16) ◽  
pp. 255-267
Author(s):  
Shaikh A. Ali ◽  
M. I. M. Wazeer ◽  
M. B. Fettouhi ◽  
M. Z. N. Iman
Keyword(s):  
Inversion Process ◽  
Nitrogen Inversion

The Synthesis and Properties of Dimethyl 1,2-Diazetine-1,2-dicarboxylate, a Potentially Aromatic Molecule

1979 ◽  
Vol 32 (12) ◽  
pp. 2659 ◽  
Author(s):  
RN Warrener ◽  
EE Nunn ◽  
MN Paddon-Row
Keyword(s):  
Ring Opening ◽  
Energy Surface ◽  
Alder Reaction ◽  
Diels Alder ◽  
Inversion Process ◽  
Nitrogen Inversion ◽  
Aromatic Character ◽  
Diels Alder Reaction ◽  
Planar Form ◽  
High Stereoselectivity

The cyclobutene n-bond of dimethyl 2,3-diazabicyclo[2,2,0]hex-5-ene-cis-2,3-dicarboxylate (15) has been employed as a dienophile in the Diels-Alder reaction with 2,5-dimethyl-3,4-diphenylcyclopenta- 2,4-dienone (17). The reaction occurred with high stereoselectivity and led, almost exclusively, to the formation of the exo-fused adduct (18). A similar cycloaddition was performed between the dienone (17) and the bicyclo[2,2,0]hex-5-ene-cis-2,3-dicarboxylic anhydride (5) to yield a 90 : 10 mixture of adducts (6). These several adducts were used as precursors for the preparation of the related bicyclo[4,2,0]octa-2,4-diene derivatives (7) and (20), themselves used as photosubstrates for the 1,2-photoaromatization reaction. In this way the carbocyclic precursor (7) yielded cyclobut-3- ene-cis-1,2-dicarboxylic anhydride (8), and the hetero analogue (20) yielded the title diazetine (21). Hydrogenation of this heterocycle yielded the related 1,2-diazetidine (22) which was fully characterized. The reactivity of the diazetine, which formally contains six delocalized electrons, is considered especially as it relates to its potential aromatic character. In practice the facile ring- opening of the diazetine to the 1,4-diazabuta-1,3-diene (23) fairly reflects the lack of aromaticity of this ring system. An INDO MO SCF method has been used to evaluate the energetics of the nitrogen inversion process in the unsubstituted 1,2-diazetine ring. The results indicate that the planar form lies at a maximum on the energy surface and that there is little electron delocalization. The planar form is best described as being antiaromatic. PMO arguments are presented which support this conclusion.

Conformational assignments and a nitrogen inversion process in some 3-acyloxy-1,3-oxazinanes by NMR and X-ray analysis

1999 ◽  
pp. 877-884 ◽  
Author(s):  
Syed M. A. Hashmi ◽  
Mohammed I. M. Wazeer ◽  
M. Sakhawat Hussain ◽  
Joseph H. Reibenspies ◽  
Herman P. Perzanowski ◽  
...  
Keyword(s):  
Inversion Process ◽  
X Ray ◽  
Nitrogen Inversion

α- vs Ortho-Lithiation ofN-Alkylarylaziridines: Probing the Role of the Nitrogen Inversion Process†

2008 ◽  
Vol 73 (23) ◽  
pp. 9214-9220 ◽  
Author(s):  
Francesco Affortunato ◽  
Saverio Florio ◽  
Renzo Luisi ◽  
Biagia Musio
Keyword(s):  
Inversion Process ◽  
Nitrogen Inversion

Microporous Membranes from an Insoluble Polyimide

1995 ◽  
Vol 60 (10) ◽  
pp. 1741-1746
Author(s):  
Jan Schauer ◽  
Miroslav Marek
Keyword(s):  
Acetic Anhydride ◽  
Phase Inversion ◽  
Amic Acid ◽  
Microporous Membranes ◽  
Inversion Process ◽  
Phase Inversion Process ◽  
Ultrafiltration Process

Poly(amic acid) prepared from 3,3',4,4'-benzophenonetetracarboxylic dianhydride and bis(4-aminophenyl) ether was used for preparation of microporous membranes by the phase inversion process. Membranes coagulated in acetic anhydride were brittle but usable for ultrafiltration. Coagulation of the poly(amic acid) in water or lower alcohols and subsequent thermal cyclocondensation led to extremely brittle polyimides, which limits their use for ultrafiltration process.

scholarly journals Low-Frequency Expansion Approach for Seismic Data Based on Compressed Sensing in Low SNR

2021 ◽  
Vol 11 (11) ◽  
pp. 5028
Author(s):  
Miaomiao Sun ◽  
Zhenchun Li ◽  
Yanli Liu ◽  
Jiao Wang ◽  
Yufei Su
Keyword(s):  
Reflection Coefficient ◽  
Compressed Sensing ◽  
Objective Function ◽  
Low Frequency ◽  
Original Data ◽  
Seismic Exploration ◽  
High Signal ◽  
Inversion Process ◽  
Frequency Information ◽  
Low Snr

Low-frequency information can reflect the basic trend of a formation, enhance the accuracy of velocity analysis and improve the imaging accuracy of deep structures in seismic exploration. However, the low-frequency information obtained by the conventional seismic acquisition method is seriously polluted by noise, which will be further lost in processing. Compressed sensing (CS) theory is used to exploit the sparsity of the reflection coefficient in the frequency domain to expand the low-frequency components reasonably, thus improving the data quality. However, the conventional CS method is greatly affected by noise, and the effective expansion of low-frequency information can only be realized in the case of a high signal-to-noise ratio (SNR). In this paper, well information is introduced into the objective function to constrain the inversion process of the estimated reflection coefficient, and then, the low-frequency component of the original data is expanded by extracting the low-frequency information of the reflection coefficient. It has been proved by model tests and actual data processing results that the objective function of estimating the reflection coefficient constrained by well logging data based on CS theory can improve the anti-noise interference ability of the inversion process and expand the low-frequency information well in the case of a low SNR.

Importance of transition-state steric strain in the nitrogen inversion of hydrazines

1974 ◽  
pp. 823 ◽  
Author(s):  
Victor J. Baker ◽  
Alan R. Katritzky ◽  
Jean-Pierre Majoral ◽  
Stephen F. Nelsen ◽  
Patrick J. Hintz
Keyword(s):  
Transition State ◽  
Steric Strain ◽  
Nitrogen Inversion
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