Facile rotation around a silicon–phosphorus double bond enabled through coordination to tungsten

Background: Vietnam currently imports up to 90% of the pharmaceuticals it consumes and 100% of the steroid-based pharmaceuticals. The ability for efficient chemical synthesis of the steroids could create commercial opportunities to address this issue. Synthesis of 21-acetoxypregna-1,4,9(11)- triene-17α,21-diol-3,20-dione is considered a key intermediate in the scheme of steroidal drug synthesis. Previous synthesis attempts of such steroids (corticoids) introduce a double bond at C-1(2) in the final stage of synthesis, which delivers a poor yield and reduces the economic efficiency of the process. Objective: To study and develop a novel and effective method for the synthesis of 21-acetoxypregna- 1,4,9(11)-triene-17α,21-diol-3,20-dione. Methods: Using 9α-hydroxyandrostenedione as a substrate chemical synthesis was performed as follows: pregnane side chain construction at C-17 (acetylene method), introduction of C-1(2) double bond (using SeO2), epimerization of C-17 (via 17-ONO2 ester) and Stork’s iodination. Results: 21-acetoxypregna-1,4,9(11)-triene-17α,21-diol-3,20-dione was prepared from 9α- hydroxyandrostenedione with an improved yield compared to previous attempts. Conclusion: Here, 21-acetoxypregna-1,4,9(11)-triene-17α,21-diol-3,20-dione has been synthesized from 9α-hydroxyandrostenedione based on a novel, effective and commercially feasible scheme. The introduction of the C-1(2) double bond at an earlier stage of the synthesis has increased the economic efficiency of the entire process. For the first time, the indirect epimerization mechanism has been clarified along with the configuration of the C-17 stereo-center which has been confirmed using NOESY data.

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Neodymium-Promoted Highly Selective Carbon–Carbon Double Bond Formation of Ketones with Allyl Halides in the Presence of Diethyl Phosphite

Synthesis ◽

10.1055/s-0040-1707219 ◽

2020 ◽

Vol 52 (22) ◽

pp. 3446-3451

Author(s):

Songlin Zhang ◽

Dengbing Xie ◽

Yiqiong Wang ◽

Bo Yang

Keyword(s):

Double Bond ◽

Bond Formation ◽

Point Of View ◽

Diethyl Phosphite ◽

Reaction Conditions ◽

One Pot ◽

Mild Conditions ◽

Carbon Double Bond ◽

Allyl Halides ◽

First Time

The carbon–carbon double bond formation via neodymium-mediated Barbier-type reaction of ketones and allyl halides in the presence of diethyl phosphite is reported for the first time. The reaction is highly α-regioselective and was conveniently carried out under mild conditions in a one-pot fashion. From a synthetic point of view, a series of conjugated alkenes were obtained in moderate to good yields in this one-pot reaction with feasible reaction conditions.

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Metal-Free Addition of Boronic Acids to Silylnitronates

Synlett ◽

10.1055/s-0039-1690845 ◽

2020 ◽

Vol 31 (09) ◽

pp. 856-860

Author(s):

Laurent El Kaïm ◽

Mansour Dolé Kerim ◽

Pakoupati Boyode ◽

Julian Garrec

Keyword(s):

Reaction Mechanism ◽

Double Bond ◽

Boronic Acids ◽

Dft Study ◽

Metal Free ◽

Nitro Derivatives ◽

Oxime Derivatives ◽

Nitrogen Double Bond ◽

First Time ◽

Aryl Transfer

We report for the first time a metal-free addition of boronic acids to silylnitronates to afford oxime derivatives through aryl transfer on the carbon nitrogen double bond. A reaction mechanism has been proposed in relation with a DFT study on the key aryl transfer. This arylation process is effective for cycloalkenyl nitro derivatives leading to oximes that may be oxidatively converted into 3-arylisoxazole derivatives.

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Synthesis of 5-arylacetylene 1,2,4-oxadiazoles and their transformations under superelectrophilic activation conditions

10.3762/bxiv.2021.49.v1 ◽

2021 ◽

Author(s):

Andrey I Puzanov ◽

Dmitry S Ryabukhin ◽

Anna S Zalivatskaya ◽

Dmitriy N Zakusilo ◽

Darya S Mikson ◽

...

Keyword(s):

Double Bond ◽

Dft Calculations ◽

Reaction Mechanisms ◽

Room Temperature ◽

Triflic Acid ◽

Activation Conditions ◽

First Time ◽

Vinyl Triflates ◽

Derivatives Of ◽

Acetylene Derivatives

Acetylene derivatives of 1,2,4-oxadiazoles, 5-(2-arylethynyl)-3-aryl-1,2,4-oxadiazoles, have been obtained, for the first time, from 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles by their bromination at the carbon-carbon double bond followed by di-dehydrobromination with NaNH2 in liquid NH3. Reaction of the acetylene 1,2,4-oxadiazoles with arenes in neat triflic acid TfOH (CF3SO3H) at room temperature for 1 h result in the formation of E-/Z-5-(2,2-diarylethenyl)-3-aryl-1,2,4-oxadiazoles as products of regioselective hydroarylation of the acetylene bond. Addition of TfOH to acetylene bond of these oxadiazoles gives rise quantitatively to E-/Z-vinyl triflates. Reaction cationic intermediates have been studied by DFT calculations. The reaction mechanisms have been discussed.

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Novel Bispidine-Monoterpene Conjugates—Synthesis and Application as Ligands for the Catalytic Ethylation of Chalcones

Molecules ◽

10.3390/molecules26247539 ◽

2021 ◽

Vol 26 (24) ◽

pp. 7539

Author(s):

Evgeniy V. Suslov ◽

Konstantin Y. Ponomarev ◽

Oxana S. Patrusheva ◽

Sergey O. Kuranov ◽

Alina A. Okhina ◽

...

Keyword(s):

Double Bond ◽

Chromatographic Analysis ◽

Enantiomeric Excess ◽

Catalytic Systems ◽

First Time

A number of new chiral bispidines containing monoterpenoid fragments have been obtained. The bispidines were studied as ligands for Ni-catalyzed addition of diethylzinc to chalcones. The conditions for chromatographic analysis by HPLC-UV were developed, in which the peaks of the enantiomers of all synthesized chiral products were separated, which made it possible to determine the enantiomeric excess of the resulting mixture. It was demonstrated that bispidine-monoterpenoid conjugates can be used as the ligands for diethylzinc addition to chalcone C=C double bond but not as inducers of chirality. Besides products of ethylation, formation of products of formal hydrogenation of the chalcone C=C double bond was observed in all cases. Note, that this formation of hydrogenation products in significant amounts in the presence of such catalytic systems was found for the first time. A tentative scheme explaining the formation of all products was proposed.

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Study of tacticity and thermal rearrangement of low molecular weight 1,2- polybutadiene by NMR

e-Polymers ◽

10.1515/epoly.2008.8.1.1357 ◽

2008 ◽

Vol 8 (1) ◽

Author(s):

Farshid Ziaee ◽

Hamid Salehi Mobarakeh ◽

Mehdi Nekoomanesh ◽

Hassan Arabi

Keyword(s):

Double Bond ◽

Theoretical Calculations ◽

Group Formation ◽

Methine Carbon ◽

Order Markov Chain ◽

Probable Reaction ◽

Cis And Trans ◽

First Time ◽

Atactic Polymer ◽

Good Agreement

AbstractLow molecular wieght 1,2-polybutadiene (Aldrich) tacticity was determined by 13CNMR (100.6 MHz). It was found that the olefinic methylene carbon has the highest splitting and a combination of pentad and heptad sequences was determined which is in agreement with the theoretical calculations. For the first time aliphatic methine carbon assignment of 1,2-polybutadiene was performed. Furthermore, olefinic methine carbon assignment was also performed and the results were compared with the theoretical calculations. For all carbons Bernoullian and first-order Markov-chain propagation statistics were used to fit the experimental data and a good agreement was obtained indicating an atactic polymer (Pm= 0.467). It was shown that the most probable reaction before gelation which happens by heating the polymer under vacuum at 250°C, is crosslinking accompanied with methyl group formation. The decrease in double bond intensity of the pendant group together with constant cis and trans double bond intensities were observed. During heating the syndiotactic triad sequences are consumed indicating that no cyclization has happened.

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N-Benzylnicotinamide and N-benzyl-1,4-dihydronicotinamide: useful models for NAD+ and NADH

Acta Crystallographica Section C Structural Chemistry ◽

10.1107/s2053229617008877 ◽

2017 ◽

Vol 73 (7) ◽

pp. 531-535 ◽

Cited By ~ 1

Author(s):

John M. Moore ◽

Jasmine M. Hall ◽

Wendell L. Dilling ◽

Anton W. Jensen ◽

Philip J. Squattrito ◽

...

Keyword(s):

Double Bond ◽

Transition State ◽

Dihedral Angle ◽

Amide Group ◽

Ene Reaction ◽

High Resolution Structure ◽

First Time ◽

Dihydropyridine Ring ◽

Methylene Group ◽

Resolution Structure

3-Aminocarbonyl-1-benzylpyridinium bromide (N-benzylnicotinamide, BNA), C13H13N2O+·Br−, (I), and 1-benzyl-1,4-dihydropyridine-3-carboxamide (N-benzyl-1,4-dihydronicotinamide, rBNA), C13H14N2O, (II), are valuable model compounds used to study the enzymatic cofactors NAD(P)+ and NAD(P)H. BNA was crystallized successfully and its structure determined for the first time, while a low-temperature high-resolution structure of rBNA was obtained. Together, these structures provide the most detailed view of the reactive portions of NAD(P)+ and NAD(P)H. The amide group in BNA is rotated 8.4 (4)° out of the plane of the pyridine ring, while the two rings display a dihedral angle of 70.48 (17)°. In the rBNA structure, the dihydropyridine ring is essentially planar, indicating significant delocalization of the formal double bonds, and the amide group is coplanar with the ring [dihedral angle = 4.35 (9)°]. This rBNA conformation may lower the transition-state energy of an ene reaction between a substrate double bond and the dihydropyridine ring. The transition state would involve one atom of the double bond binding to the carbon ortho to both the ring N atom and the amide substituent of the dihydropyridine ring, while the other end of the double bond accepts an H atom from the methylene group para to the N atom.

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A Novel Taxatetraene Framework Formed From a New Natural Taxane from Taxus cuspidata

Zeitschrift für Naturforschung B ◽

10.1515/znb-2011-0721 ◽

2011 ◽

Vol 66 (7) ◽

pp. 759-761

Author(s):

Yong Li ◽

Yong-Li Wang ◽

Zhi-Yu Ni ◽

Mei Dong ◽

Bin Cong ◽

...

Keyword(s):

Double Bond ◽

Taxus Cuspidata ◽

Natural Sources ◽

Conjugated Triene ◽

First Time

Sinenxan H [2α,14β -diacetoxytaxa-4(20),11-diene-5α, 10β -diol, 1] was isolated from the heartwood of Taxus cuspidata, for the first time from natural sources. Compound 1 was found to be readily converted into 2α-acetoxytaxa-4(20),10,12(18),13-tetraen-5α-ol (2), the first example of a taxane with 10,11- and/or 13,14-double bond(s) and a conjugated triene system, in CDCl3.

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Effects of Different Phases of Cigarette Smoke on Lipid Peroxidation and Membrane Structure in Liposomes

Australian Journal of Chemistry ◽

10.1071/ch13663 ◽

2014 ◽

Vol 67 (6) ◽

pp. 858 ◽

Cited By ~ 4

Author(s):

Nadezhda P. Palmina ◽

Elena L. Maltseva ◽

Tatyana E. Chasovskaya ◽

Valery V. Kasparov ◽

Nataliya G. Bogdanova ◽

...

Keyword(s):

Lipid Peroxidation ◽

Double Bond ◽

Gas Phase ◽

Lipid Bilayer ◽

Cigarette Smoke ◽

Membrane Structure ◽

Malonic Dialdehyde ◽

Oxidation Products ◽

Liposomal Membranes ◽

First Time

This paper discloses for the first time the effects of the gas phase (GP) and the tar of cigarette smoke on lipid peroxidation (LPO) and on the structure of different lipid regions in liposomes. The LPO development was analysed in terms of the total unsaturation of lipids (double-bond, DB, content) and the formation of dienic conjugates (DC), ketodienes (KD), and malonic dialdehyde (MDA). As expected, the exposure of liposomes to either the GP or the tar led to a significant decrease in the DB content. However, the formation of oxidation products revealed different dynamics: MDA generation was inhibited, while the formation of DC and KD increased during the first few hours of the LPO development followed by its inhibition. The smoke constituents exhibited opposite effects on the structure of the lipid bilayer of liposomes: the GP markedly enhanced the microviscosity of liposomal membranes, whereas the tar caused a drastic lowering of microviscosity.

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Synthetic Studies Concerning the Crinine Alkaloid Haemultine

Australian Journal of Chemistry ◽

10.1071/ch12473 ◽

2013 ◽

Vol 66 (1) ◽

pp. 30 ◽

Cited By ~ 9

Author(s):

Nadia (Yuqian) Gao ◽

Xinghua Ma ◽

Laurent Petit ◽

Brett D. Schwartz ◽

Martin G. Banwell ◽

...

Keyword(s):

Double Bond ◽

Natural Product ◽

Trifluoroacetic Acid ◽

Spectroscopic Data ◽

Ene Reaction ◽

Enantiomerically Pure ◽

Racemic Form ◽

Pure Compounds ◽

First Time ◽

Bond Isomer

The racemic form, (±)-1, of the structure originally assigned to the crinine alkaloid haemultine has been prepared for the first time. A key step involved the conversion of compound (±)-4 into the isomeric cis-C3a-arylhexahydroindole (±)-3 using a Pd0-catalysed intramolecular Alder-ene reaction. The amino-alcohol (±)-2 derived from the latter compound reacted with paraformaldehyde in the presence of trifluoroacetic acid to give, via a Pictet–Spengler reaction, the target (±)-1. The diastereoisomeric Mosher esters 15 and 16 obtained by coupling the racemate (±)-1 with the R-form, 14, of the Mosher acid could be separated chromatographically and then reductively cleaved to give the enantiomerically pure compounds (+)-1 and (–)-1, respectively. The physical and spectroscopic data derived from the former enantiomer are consistent with the proposition that the title natural product is, in fact, a mixture of (+)-1 and its Δ2,3-double bond isomer.

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