New 1,3-dihydroazepin-2-one derivatives by [3,3]-sigmatropic rearrangement of suitably substituted 2-alkenylcyclopropyl isocyanates

2004 ◽  
Vol 82 (2) ◽  
pp. 166-176 ◽  
Author(s):  
Hans-Ulrich Reissig ◽  
Gesine Böttcher ◽  
Reinhold Zimmer
Keyword(s):  
Sigmatropic Rearrangement ◽  
Similar Reaction ◽  
Model Compounds ◽  
Double Bond Migration ◽  
Proton Shift ◽  
Sigmatropic Rearrangements ◽  
Primary Products ◽  
Curtius Reaction ◽  
Reaction Barriers ◽  
Final Proton

The 2-siloxysubstituted 2-alkenylcyclopropanecarboxylic acids 10–14 were converted into the corresponding carbonyl azides by treatment with DPPA (diphenyl phosphorazidate) and triethylamine. On heating to 80 °C these intermediates smoothly furnished azepinone derivatives 19–25 in moderate to good overall yields, which are the result of a sequence of Curtius reaction to cyclopropylisocyanates, [3,3]-sigmatropic rearrangement, and a final proton shift. The primary products may undergo desilylation (to afford azepin-2,5-diones such as 23) or double bond migration (to compound 25). Cyclopropanecarboxylic acids cis-32, cis-34, and cis-35, which bear no 2-siloxy group, similarly provided azepinone derivatives 36–38 in good yields. No influence of the 2-siloxy substituent on the reaction course and rates could be observed in these qualitative studies, which was confirmed by DFT calculations with model compounds 39–42 showing similar reaction barriers for rearrangements of cyclopropylisocyanates with or without a 2-hydroxy group.Key words: vinyl cyclopropanes, carbonylazides, [3.3]-sigmatropic rearrangements, azepinones.

Synthesis of new substituted dihydroheptalene derivatives: SiO2- and base-catalyzed rearrangement of dimethyl trans-3,8-dihydroheptalene-3,8-dicarboxylate

2001 ◽  
Vol 79 (1) ◽  
pp. 35-41
Author(s):  
Nurullah Saraçoglu ◽  
Abdullah Menzek ◽  
Armagan Kinal ◽  
Metin Balci
Keyword(s):  
Room Temperature ◽  
Heat Of Formation ◽  
Major Product ◽  
Similar Reaction ◽  
Am1 Calculations ◽  
Hydrogen Shift ◽  
Proton Shift ◽  
Major Isomer ◽  
Prolonged Reaction Time ◽  
Lower Heat

Dimethyl trans-3,8-dihydroheptalene-3,8-dicarboxylate (trans-3) isomerizes to dimethyl cis-3,8-dihydroheptalene-3,8-dicarboxylate (cis-3) upon treatment with SiO2. On the other hand, base-catalyzed reaction of trans-3 undergoes a direct 1,3-intramolecular proton shift to give 6 at room temperature in 5 min. Prolonged reaction time formed isomers 7 and 8 in a ratio of 4:1. AM1 calculations indicate that the isomer 8, which is formed as minor product, has a lower heat of formation (–99.34 kcal mol–1) than that of the major isomer 7 (–92.05 kcal mol–1). However, when a similar reaction was performed at 100°C, the thermodynamically more stable isomer 8 was formed as the major product. Furthermore, cycloaddition reactions of these new dihydroheptalene derivatives 6 and 7 with different dienophiles have been studied. The mechanism has been discussed.Key words: dihydroheptalene, cycloaddition, 1,3-hydrogen shift, cycloheptatriene–norcaradiene equilibrium.

Part 2: Efficient strategies for the construction of variably substituted bicyclo[5.3.1]undecenones (AB-taxane ring systems) and their conversion to tricyclo[9.3.1.03,8]pentadecenones (ABC taxane ring systems) and bicyclo[2.2.2]octanones

2004 ◽  
Vol 82 (2) ◽  
pp. 227-239 ◽  
Author(s):  
Nidia P Villalva-Servín ◽  
Alain Laurent ◽  
Alex G Fallis
Keyword(s):  
Lewis Acid ◽  
Sigmatropic Rearrangement ◽  
Diels Alder ◽  
Direct Access ◽  
Cope Rearrangement ◽  
Ring Closing Metathesis ◽  
Ring Systems ◽  
Sigmatropic Rearrangements ◽  
Key Words Magnesium ◽  
Cope Rearrangements

The extension of our strategies for the construction of cyclic molecules containing variably substituted bicyclo[5.3.1]undecenones (AB taxane ring systems) for the synthesis of the tricyclo[9.3.1.03,8]pentadecenone (ABC taxane ring system) and bicyclo[2.2.2]octanones are described. These routes employ a multi-component coupling protocol that employs sequential magnesium-mediated carbometallation of allyl-substituted propargyl alcohols followed by diastereoselective Lewis acid catalyzed intramolecular Diels–Alder reactions (IMDA). Subsequent ring-closing metathesis (RCM) afforded the ABC taxane core structure. Enone accelerated [3,3] sigmatropic rearrangements (Cope rearrangements) generated the bicyclo[2.2.2]octanone nucleus. In the presence of a Lewis acid, the dienophile precursor underwent a tandem reaction via the adduct directly to the bicyclo[2.2.2]octanones. This is the first example of a novel enone accelerated carbocycle Cope rearrangement and provides direct access to bicyclo[2.2.2]octanones by a new route that compliments the traditional cyclohexadiene cycloaddition approach. Key words: magnesium chelate, Lewis acid, taxanes, Diels–Alder, sigmatropic rearrangement, oxy-Cope, ring-closing metathesis, bicyclo[2.2.2]octanone.

Nucleic acid related compounds. 77. 2′,3′-Didehydro-2′,3′-dideoxy-2′(and 3′)-methylnucleosides via [3,3]-sigmatropic rearrangements of 2′(and 3′)-methylene-3′(and 2′)-O-thiocarbonyl derivatives and radical reduction of a 2′-chloro-3′-methylene analogue

1993 ◽  
Vol 71 (2) ◽  
pp. 186-191 ◽  
Author(s):  
Vincente Samano ◽  
Morris J. Robins
Keyword(s):  
Nucleic Acid ◽  
Sigmatropic Rearrangement ◽  
Sigmatropic Rearrangements ◽  
Radical Reduction ◽  
Adenosine Derivatives ◽  
Related Compounds

Treatment of 5′-O-(tert-butyldiphenylsilyl)-2′(and 3′)-deoxy-2′(and 3′)-methyleneuridine (and adenosine) derivatives with phenyl chlorothionocarbonate gave the 3′(and 2′)-O-phenoxythiocarbonyl intermediates, which underwent spontaneous [3,3]-sigmatropic rearrangement to give the 2′,3′-didehydro-2′,3′-dideoxy-2′(and 3′)-(phenoxycarbonylthio)methyl analogues. These allylic thioesters were subjected to tributylstannane-mediated hydrodesulfurization and deprotection to give 2′,3′-didehydro-2′,3′-dideoxy-2′(and 3′)-methyluridine (and adenosine). Tributylstannane-mediated hydrodehalogenation of a 2′-chloro-2′,3′-dideoxy-3′-methyleneuridine derivative afforded the 2′,3′-didehydro-2′,3′-dideoxy-3′-methyl product of allylic transposition exclusively.

Flash thermolysis: multiple sigmatropic rearrangements in ortho-substituted aromatic compounds

1976 ◽  
Vol 54 (23) ◽  
pp. 3749-3756 ◽  
Author(s):  
Pierre de Champlain ◽  
Jean-Louis Luche ◽  
Robert A. Marty ◽  
Paul de Mayo
Keyword(s):  
Benzyl Alcohol ◽  
Methyl Ether ◽  
Aromatic Compounds ◽  
Sigmatropic Rearrangement ◽  
Methyl Anthranilate ◽  
Rearrangement Product ◽  
Sigmatropic Rearrangements

A number of o-disubstituted benzenoid substances on flash thermolysis undergo 1,4-elimination of water or alcohols to yield o-quinonoid derivatives. Those products possessing a pentadienyl hydrogen subsequently undergo a 1,5-sigmatropic rearrangement: in many cases the rearrangement product undergoes yet further transformations, such as addition or hydrolysis, and such reactions have been used for their characterization. Included are: the conversion of N-methyl anthranilate esters to o-aminobenzaldehyde; o-(N-methyl)benzyl alcohol and methyl ether to o-toluidine; o-methoxymethylformanilide to o-tolyl isocyanate; and o-carboxymethylformanilide to o-aminobenzaldehyde.

[3,3]- Versus [1,3]-Sigmatropic Rearrangement of O-Substituted Allyl N-Acylmonothiocarbamates

1994 ◽  
Vol 59 (12) ◽  
pp. 2650-2662 ◽  
Author(s):  
Vlastimír Ficeri ◽  
Peter Kutschy ◽  
Milan Dzurilla ◽  
Ján Imrich
Keyword(s):  
Double Bond ◽  
Benzyl Alcohol ◽  
Sigmatropic Rearrangement ◽  
Allylic Alcohols ◽  
Cinnamyl Alcohol ◽  
Aromatic System ◽  
Sigmatropic Rearrangements ◽  
Sigmatropic Shift

Substituted allylic alcohols (2-buten-1-ol, 1-buten-3-ol, cinnamyl alcohol and 3-methyl-2-buten-1-ol) react with acyl isothiocyanates (4-chlorobenzoyl, 2,6-difluorobenzoyl, 3-phenylpropenoyl, 2-thienocarbonyl, 3-chloro-2-thienocarbonyl and 3-chloro-2-benzo[b]thienocarbonyl isothiocyanate) with the formation of highly reactive O-substituted allyl N-acylmonothiocarbamates, which either spontaneously or by heating in boiling benzene undergo [3,3]-sigmatropic rearrangement to S-substituted allyl N-acylmonothiocarbamates. The structure of S-esters with isomerized allylic group affords the unequivocal evidence of the [3,3]-sigmatropic route of studied rearrangement. Further heating of [3,3]-rearranged N-(4-chlorobenzoyl)monothiocarbamates results in the [1,3]-sigmatropic shift of monothiocarbamate group. Using arylalkyl alcohols with the allylic double bond inserted into an aromatic system the obtained O-esters either do not undergo any rearrangement (benzyl alcohol) or undergo [1,3]-sigmatropic rearrangement (2- and 3-furylmethanol and 1-(2-furyl)ethanol) to the corresponding S-esters. For explanation of this reaction the tandem of [3,3]- and [1,3]-sigmatropic rearrangements is suggested.

Reactions of Lignin with Peroxymonophosphoric Acid: The Degradation of Lignin Model Compounds

Holzforschung ◽  
2003 ◽  
Vol 57 (1) ◽  
pp. 44-51 ◽  
Author(s):  
T. Zhu ◽  
J. F. Kadla ◽  
H.-m. Chang ◽  
H. Jameel
Keyword(s):  
Initial Step ◽  
Reaction Rates ◽  
Nucleophilic Attack ◽  
Initial Reaction ◽  
Similar Reaction ◽  
Kraft Pulps ◽  
Model Compounds ◽  
Lignin Model Compounds ◽  
Lignin Model ◽  
Methyl Benzene

Summary Peroxymonophosphoric acid (Pp) has been shown to be an excellent delignification chemical for kraft pulps. However, the reaction mechanism of Pp with lignin has not been elucidated. Therefore, the reactions of Pp with non-phenolic lignin model compounds have been investigated at 70 and 90°C and compared to those of peroxymonosulfuric acid (Px). Pp and Px appear to follow similar reaction pathways, however, the reaction kinetics are significantly different. Both Pp and Px react with 1,2-Dimethoxy-4-methyl-benzene as electrophiles, with aromatic hydroxylation being the main initial reaction. For 1-(3,4-Dimethoxy-phenyl)-ethanone, both Px and Pp react via the Baeyer-Villiger reaction, in which the initial step is nucleophilic attack by the peracid.The reaction with 1-(3,4-Dimethoxy-phenyl)-ethanol occurs primarily via carbocation formation followed by subsequent reactions with the peracid. Changes in pH dramatically affect the reaction rates of Pp with all the model compounds investigated, whereas with the exception of the Baeyer-Villiger reaction, changes in pH did not affect the Px reactions. Below pH 2, Pp is a better electrophile than Px, but above pH 2, Px is better. In addition, while Px remains reactive, Pp is not reactive at pH above 7 for the model compounds investigated.

Réactivité dipolaire-1,3 du 4,4,4-trichiloro-3-éthoxycarbonylamino-2-diazobutyrate d'éthyle issu de l'action du diazoacétate d'éthyle sur la N-éthoxycarbonyl-N-(2,2,2-trichloroéthylidène)amine

1997 ◽  
Vol 75 (5) ◽  
pp. 523-530 ◽  
Author(s):  
Abdelhak Belaissaoui ◽  
Sandrine Jacquot ◽  
Claude Morpain ◽  
Gérard Schmitt ◽  
Joël Vebrel ◽  
...  
Keyword(s):  
Nucleophilic Addition ◽  
Cycloaddition Reaction ◽  
Diazo Compound ◽  
Sigmatropic Rearrangement ◽  
Dipolar Cycloaddition ◽  
Acetylenic Esters ◽  
Ethyl Diazoacetate ◽  
Sigmatropic Rearrangements ◽  
Nitrogen Elimination ◽  
Substituted Pyrazoles

The reaction of ethyl diazoacetate with the N-ethoxycarbonyl-N-(2,2,2-trichloroethylidene)amine yields, by a nucleophilic addition, a new diazo compound that gives 1,3-dipolar cycloaddition reactions with acetylenic esters and maleimides. With acetylenic esters, the cycloadduct leads to substituted pyrazoles by [1,5] sigmatropic rearrangements. With maleimides, we observe a diastereospecific cycloaddition reaction. The intermediary cycloadduct evolves by nitrogen elimination to give a maleimidocyclopropane. The diastereospecificity was explained by an endo-anti approach of the reactants. Keywords: N-ethoxycarbonyl-N-(2,2,2-trichloroethylidene)amine, ethyl diazoacetate, nucleophilic addition, 1,3-dipolar cycloaddition, sigmatropic rearrangement, diastereoselectivity.

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