Thermal intramolecular reactions of Δ1-1,2,4-triazolines with extended exocyclic unsaturation

1988 ◽  
Vol 66 (3) ◽  
pp. 385-390 ◽  
Author(s):  
Adrian L. Schwan ◽  
John Warkentin
Keyword(s):  
Ring Opening ◽  
Hydrolysis Product ◽  
Sigmatropic Rearrangement ◽  
Membered Ring ◽  
Ring Closure ◽  
Experimental Results ◽  
First Order ◽  
Ring Opening Reaction ◽  
Intramolecular Reactions

Fumaratotriazoline (1) and amidotriazoline (3) undergo thermal first-order transformations in solution at 65 °C. The former affords the isomeric pyrrole 5 and its hydrolysis product 6. A mechanism involving opening of the initial five-membered ring to form 8, followed by closure to a new five-membered ring (9), is proposed. Amidotriazoline (3) loses N2 on heating to form 19. The experimental results are best accommodated in terms of a novel mechanism involving an electrocyclic ring closure, a [3 + 2] cycloreversion to form an ylide, a sigmatropic rearrangement of the ylide, and, finally, an electrocyclic ring-opening reaction.

First Total Synthesis of a Fluorinated Calystegin

2010 ◽  
Vol 65 (4) ◽  
pp. 445-451 ◽  
Author(s):  
René Csuk ◽  
Erik Prell ◽  
Stefan Reißmann ◽  
Claudia Korb
Keyword(s):  
Total Synthesis ◽  
Ring Opening ◽  
Competitive Inhibitor ◽  
Ring Closure ◽  
Target Compound ◽  
Metathesis Reaction ◽  
Grubbs Catalyst ◽  
Ring Opening Reaction ◽  
Ultrasound Assisted ◽  
Key Steps

A straightforward chiral pool synthesis for the first fluorinated calystegin is described. Key steps of this synthesis include an ultrasound-assisted Zn-mediated tandem ring opening reaction followed by a Grubbs’ catalyst-mediated ring closure metathesis reaction. The target compound is a selective and competitive inhibitor for a β -glycosidase.

scholarly journals Bidirectional cross metathesis and ring-closing metathesis/ring opening of a C 2-symmetric building block: a strategy for the synthesis of decanolide natural products

2013 ◽  
Vol 9 ◽  
pp. 2544-2555 ◽  
Author(s):  
Bernd Schmidt ◽  
Oliver Kunz
Keyword(s):  
Building Block ◽  
Ring Opening ◽  
Kinetic Resolution ◽  
Membered Ring ◽  
Ring Closure ◽  
Ring Closing Metathesis ◽  
Cross Metathesis ◽  
Key Steps ◽  
A Site ◽  
Site Selective

Starting from the conveniently available ex-chiral pool building block (R,R)-hexa-1,5-diene-3,4-diol, the ten-membered ring lactones stagonolide E and curvulide A were synthesized using a bidirectional olefin-metathesis functionalization of the terminal double bonds. Key steps are (i) a site-selective cross metathesis, (ii) a highly diastereoselective extended tethered RCM to furnish a (Z,E)-configured dienyl carboxylic acid and (iii) a Ru–lipase-catalyzed dynamic kinetic resolution to establish the desired configuration at C9. Ring closure was accomplished by macrolactonization. Curvulide A was synthesized from stagonolide E through Sharpless epoxidation.

Intermediates from ring-opening reactions. Reactions of 2-chloro-5-nitropyridine and 2-chloro-3-nitropyridine with deuteroxide ion in selected solvents

1984 ◽  
Vol 62 (6) ◽  
pp. 1120-1123 ◽  
Author(s):  
John D. Reinheimer ◽  
Nicolas Sourbatis ◽  
Robert L. Lavallee ◽  
Douglas Goodwin ◽  
George L. Gould
Keyword(s):  
Ring Opening ◽  
Pyridine Ring ◽  
Ring Closure ◽  
Polar Solvents ◽  
Open Chain ◽  
Decomposition Products ◽  
Aqueous Sodium ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions ◽  
Kinetics Of

Open chain intermediates from the ring-opening reaction of aqueous sodium deuteroxide (2 mol) with 2-chloro-5-nitropyridine (1 mol) and 2-chloro-3-nitropyridine (1 mol) were isolated. These intermediates were purified, analyzed for elemental composition, and characterized by various spectrophotometric techniques. The intermediate formed from 2-chloro-5-nitropyridine and two equivalents of deuteroxide ion reacts with additional deuteroxide in D2O in various polar solvents to reclose the pyridine ring. The kinetics of the ring closure reaction are reported and are supplemented with observations of salt and solvent effects upon the rate of closure. In addition, a mechanism for the ring closure is presented. The intermediate formed from 2-chloro-3-nitropyridine did not undergo a similar ring closure when reacted with additional deuteroxide, but instead formed various decomposition products. A reason for the failure of this ring closure is suggested.

A Novel Synthesis of 3-Bromo-1,2-Propanediol from 3-Oxetanol

2013 ◽  
Vol 848 ◽  
pp. 219-222
Author(s):  
Jian Sun ◽  
Shan Shan Gong ◽  
Qi Sun
Keyword(s):  
Mild Condition ◽  
Ring Opening ◽  
Experimental Results ◽  
Carbon Tetrabromide ◽  
Reaction Condition ◽  
Novel Synthesis ◽  
Ring Opening Reaction ◽  
Efficient Route ◽  
Bromination Reaction

Treatment of 3-oxetanol with carbon tetrabromide (CBr4) and triphenylphosphine (PPh3) under mild condition provides an efficient route for synthesis of 3-bromo-1,2-propanediol. The experimental results showed that an unexpected ring-opening reaction was selectively achieved under the routine bromination reaction condition.

scholarly journals REACTION OF 2-HETARYL-2-(DIHYDROFURAN-2(3H)-ILIDEN)ACETONITRILES WITH AROMATIC AMINES

2020 ◽  
pp. 47-51
Author(s):  
R. Shemehen ◽  
O. Khilya ◽  
Yu. Volovenko
Keyword(s):  
Aromatic Amines ◽  
Ring Opening ◽  
Catalytic Amount ◽  
Building Blocks ◽  
Heterocyclic Ring ◽  
Ring Closure ◽  
Reaction Conditions ◽  
Ring Opening Reaction ◽  
Ring Transformations ◽  
High Yields

This article reports on the reaction of 2-hetaryl-2-(furanyl-2-ylidene)acetonitriles with aromatic amines as N-nucleophiles. 2-Hetaryl-2-(furanyl-2-ylidene)acetonitriles represent versatile building blocks in syntheses of ω-(N-aryl)alkyl substituted heterocycles due to the presence of 1,3-bielectrophilic acrylonitrile fragment functionalized with unsaturated heterocyclic ring and nucleophilic azaheterocyclic moiety. The carbonyl group masked within the N-arylpyrrolidinylidene fragment which undergoes a ring opening through the reaction with nucleophiles. So, a method for the synthesis of 2-hetaryl-6-hydroxy-3-(arylamino)hex-2-enenitriles and 2-hetaryl-2-(N-arylpyrrolidin-2-ylidene)acetonitriles has been developed by us. The proposed scheme is based on the available reagents using. As a result of Michael addition, the aromatic amines to 2-hetaryl-2-(furanyl-2-ylidene)acetonitriles followed by ring transformations has formed two types of products, depending on the reaction conditions. The reaction of substituted furanylylideneacetonitriles with aromatic amines proceeds in good to high yields affording the corresponding 3-(arylamino)hex-2-enenitriles and 2-(N-arylpyrrolidin-2-ylidene)acetonitriles derivatives. The stereochemistry of the ring-opening reaction follows the rules of a classical SN2 mechanism. The resulting linear products can be cyclized to 2-hetaryl-2-(furanyl-2-ylidene)acetonitriles in high yields by treatment with the catalytic amount of acid or the equimolar amount of aromatic amines. Under these conditions 2-hetaryl-6-hydroxy-3-(arylamino)hex-2-enenitriles arising from reaction gives the ring closure. Since both ring-opening and cyclisation occur with fixed stereochemistry the reaction appears a valuable modification to the preparation of acetonitriles derivatives.

scholarly journals Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

2020 ◽  
Vol 16 ◽  
pp. 904-916
Author(s):  
Phil M Pithan ◽  
Sören Steup ◽  
Heiko Ihmels
Keyword(s):  
Ring Opening ◽  
Oxidation Reaction ◽  
Mass Spectrometric ◽  
Ring Closure ◽  
Fluorimetric Detection ◽  
Broad Absorption ◽  
Broad Absorption Band ◽  
Ring Opening Reaction ◽  
Screening Assays ◽  
Photochemical Properties

Two new spiroindolinonaphthoxazine derivatives with an electron-accepting styrylquinolizinium or styrylcoralyne unit, respectively, were synthesized, and the influence of such an arylvinyl substituent on the chemical and photochemical properties of the compounds was investigated. Specifically, these spirooxazines turned out to be resistant towards the photoinduced merocyanine formation, and the irradiation with light mainly led to photodegradation of the substrates. However, it was shown by colorimetric and fluorimetric screening assays as well as by detailed NMR spectroscopic and mass spectrometric studies that the addition of particular metal ions (Cu2+, Fe3+, and to a certain extent Hg2+) initially induced a ring-opening reaction that was irreversibly followed by a fast ring closure–deprotonation–oxidation sequence to give styryl-substituted naphthoxazole derivatives as the products quantitatively. For the quinolizinium-substituted spirooxazine derivative, the formation of the respective oxidation product caused the development of a broad absorption band between 425 nm and 500 nm and a new emission band at λfl = 628 nm, so that it may be employed as a selective chemosensor or chemodosimeter for the colorimetric and fluorimetric detection of Cu2+ and Fe3+.

A Stereochemical and Kinetic Study of the Conversion of Methyl Cyclopropyl Ketones to 4,5-Dihydrofurans

1973 ◽  
Vol 51 (10) ◽  
pp. 1487-1493 ◽  
Author(s):  
Donald Edward McGreer ◽  
James William McKinley
Keyword(s):  
Kinetic Study ◽  
Ring Opening ◽  
Photochemical Reactions ◽  
Order Reaction ◽  
Ring Closure ◽  
Hydrogen Shift ◽  
First Order ◽  
Bond Rotation ◽  
Cyclopropyl Ketones ◽  
Cis And Trans

The thermal and photochemical conversion of (1R*,2R*,3S*), (1S*,2R*,3S*), and (1S*,2R*,3R*)-1-acetyl-1,2-dimethyl-3-phenylcyclopropane (1, 2, and 3) to cis- and trans-2,3,4-trimethyl-5-phenyl-4,5-dihydrofurans has been studied. Concurrent with this reaction is an equilibration of 1, 2, and 3, a thermal ring opening of 1 by a 1,5-hydrogen shift, and a cyclopropane-to-propene type reaction under the photochemical conditions. The dihydrofuran from 1 and 2 by the thermal and photochemical conditions is 97% trans- and 3% cis- corresponding to predominant retention at the migrating carbon. The dihydrofuran formed from 3 by the thermal and photochemical reaction is 85% cis- and 15% trans- again corresponding to predominant retention. A kinetic study of the rearrangement of 1-acetyl-1-methyl-2-phenylcyclopropane to 1,2-dimethyl-5-phenyl-4,5-dihydrofuran provides Ea of 48.1 kcal/mol and log A of 14.9 for this first order reaction in the temperature range of 255–288 °C.It is concluded that the thermal and photochemical reactions occur by a non-concerted process through a common 1,3-diradical intermediate in which bond rotation and ring closure steps are competitive.

scholarly journals A Theoretical and Experimental Study on Esterification of Citric Acid with the Primary Alcohols and the Hydroxyl Groups of Cellulose Chain (n = 1-2) in Parched Condition

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Dang T. Nguyen ◽  
Quan T. Pham
Keyword(s):  
Citric Acid ◽  
Ring Opening ◽  
Density Functional ◽  
Membered Ring ◽  
Hydroxyl Groups ◽  
Dehydration Reaction ◽  
Primary Alcohols ◽  
Reaction Step ◽  
Cellulose Chain ◽  
Ring Opening Reaction

Esterification of citric acid (CA) with the primary alcohols and the hydroxyl groups of cellulose chain (n = 1-2) in parched condition were investigated by using density functional theory (DFT) method and a two-layer ONIOM approach. Geometry and energy of reactants, products, and transition state (TS) structures were optimized at B3LYP/6-311g (d, p) level and ONIOM (B3LYP/6-311g (d, p):PM3MM) level. The computational results show that the esterification occurs in the two main steps: the first step is the dehydration reaction of CA to form anhydrides of 5-membered ring and 6-membered ring and the second step is the ring opening reaction with the hydroxyl –OH groups to form the ester products. The energy barrier of dehydration reaction step is much higher than that of ring opening reaction step. Effect of substituent R in primary alcohol R-CH2OH (R: CH=CH2, CH2NHCH3, CH2OCH3, CH2Cl) and cellulose chain (1G, 2G) on the reactivity, which has negative inductive effect –I, is significant. The combination of calculation data and experiment data were applied to make findings more rigorous. The activation energy of CA was determined by using differential scanning calorimetry (DSC) and thermal gravimetric (TG) analysis to be E a exp  = 47.8 kcal/mol; the experimental data favoured the dehydration reaction step of CA.

Synthesis and Properties of 1-(3,5-dimethyl-4-isoxazole)-2-(2-methyl-(5-ethynyl)-3-thienyl)perfluorocyclopentene

2014 ◽  
Vol 1078 ◽  
pp. 82-85
Author(s):  
Mei Li Cai ◽  
Zhao Yan Tian ◽  
Shi Qiang Cui ◽  
Shou Zhi Pu
Keyword(s):  
Response Time ◽  
Ring Opening ◽  
Color Change ◽  
Uv Light ◽  
Order Reaction ◽  
First Order Reaction ◽  
Fluorescence Properties ◽  
First Order ◽  
Ring Opening Reaction ◽  
Hexane Solution

A new photochromic diarylethene of 1-(3,5-dimethyl-4-isoxazole)-2- (2-methyl-(5-ethynyl)-3-thienyl) perfluorocyclopentene (1o) was synthesized. Its photochromic and fluorescence properties were investigated systematically. Upon irradiation with UV light with the extended response time, the diarylethene underwent a ring opening reaction to produce closed forms and color change in solution. The results showed the compound exhibited good photochromism in hexane solution. The kinetic experiments showed that the cyclization and cycloreversion processes were zeroth and first order reaction, respectively. Moreover, diarylethene1oalso exhibited obviously fluorescence switches along with the photochromism.

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