[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.

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.

scholarly journals REACTION OF PYRIDO[2,1-a]ISOINDOLE WITH З (R)- AND (S)- N-α-METHILBENZYLMALEIMIDE

2020 ◽  
pp. 44-47
Author(s):  
T. Yegorova ◽  
B. Barnych ◽  
Z. Voitenko
Keyword(s):  
Double Bond ◽  
Reaction Pathway ◽  
Twist Angle ◽  
Alder Reaction ◽  
Sigmatropic Rearrangement ◽  
Diels Alder ◽  
Exocyclic Double Bond ◽  
Slow Rotation ◽  
Diels Alder Reaction ◽  
Sigmatropic Shift

Selective chemical reactions create new possibilities for controlled synthesis of compounds with pre-designed properties for further use in medical chemistry, material science and other fields. This is especially useful for such synthetic methodology as [4+2] cycloaddition. Current work is dedicated to study of reactions between N-chiral maleinimides with cyclic dienes based on the pyridoisoindol. Pyrido[2,1-a]isoindol turned out to be the most practical object to study the first example of asymmetric variant of the Diels-Alder reaction involving condensed isoindols. Previously, we established that this heterocyclic system, in contrast to other azino- and azoloisoindols, upon undergoing cycloaddition with non-chiral maleinimides gives only rearranged adducts of the first type. This type of compounds have also interesting stereochemistry: in solid state they have twisted double bond (twist angle 7-10°), while in solution they exist as a mixture of athropodiastereomeres due to the asymmetric Carbon atom and hindered rotation around С–С bond between exocyclic double bond and 2-(α-pyridil)phenyl fragment. Initial expectation was that chiral induction would influence the ratio of corresponding athropodiastereomeres. Calculations show that there are four possible athropodiastereomeres due to the chiral center and sterically hindered chiral axis. In case of non-chiral dienophiles, reaction results in two major diastereomeres (for our purposes marked as A and B) with 70:30 ration and two minor isomers (marked С and D respectively), the latter constituting less than 5% of the total amount. Major and minor isomers are in constant complex equilibrium, controlled via slow rotation of around corresponding С-С bond on one hand (which is the reason for athropodiastereomeres between major forms A and B, shown via NMR spectra at different temperatures), and on the other hand – fast equilibrium due to the 1,5-sigmatropic shift (cause for the minor forms C and D). Target reaction was studied under standard conditions for this rearrangement and under the kinetic control in the inert atmosphere at -80°С using TiCl4 as catalyzer. We therefore show that reaction pathway is similar to our previous examples and results in rearranged adducts of the first type. Ratio of athropodiastereomeres (both major and minor forms) is different from previous examples using non-chiral 2-substituted maleimides. Asymmetric induction spontaneously transfers from influencing the Diels-Alder reaction to influencing synchronic sigmatropic rearrangement, which is the final stage in the formation of the rearranged adduct of the first type in condensed isoindol systems.

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.

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