Unusual ortho-Claisen rearrangements of aryl prop-2-ynyl sulphoxides

Majumdar, K. C.; Thyagarajan, B. S.

doi:10.1039/c39720000083

Cited by 30 publications

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“…A recent review on this transformation is available, 8 disclosing that it was first reported in 1972 as result of the PhD work of K. C. Majumdar under the supervision of Professor B. S. Thyagarajan. 9,10 As summarized in that review, this synthetic strategy has been scarcely utilized, almost exclusively by the research groups of its two discoverers. This is why, as indicated in the title of this article, we propose this type of one-pot conversion of aryl propargyl sulfoxides into benzo[b]thien-3-yl ketones to be named as the Thyagarajan-Majumdar tandem cyclization.…”

Section: Resultsmentioning

confidence: 99%

Unexpected new examples of the Thyagarajan-Majumdar tandem cyclization of aryl propargyl sulfoxides

Alajarı́n¹,

Marín‐Luna²,

Vidal³

2013

Arkivoc

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Dedicated to Prof. Rosa M. Claramunt on the occasion of her 65th anniversary AbstractWe observed an unexpected cyclization of aryl propargyl sulfoxides to 1-benzothiophenes while attempting the in situ preparation of a particular class of allenyl sulfoxides as substrates for intramolecular hydride-shift experiments. A mechanistic rationale for explaining this result, involving a sequence of [2,3] and [3,3] sigmatropic rearrangements and a final conjugate addition, is provided by the previous work of Thyagarajan and Majumdar.

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Section: Resultsmentioning

confidence: 99%

Unexpected new examples of the Thyagarajan-Majumdar tandem cyclization of aryl propargyl sulfoxides

Alajarı́n¹,

Marín‐Luna²,

Vidal³

2013

Arkivoc

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“…The 1-aryloxy-4-chlorobut-2-ynes (2a-2f) were prepared according to published procedures (14)(15)(16).…”

Section: Methodsmentioning

confidence: 99%

Regioselective synthesis of biologically interesting pentacyclic polyheterocycles by sequential thio-Claisen and AlCl₃ catalyzed oxy-Claisen rearrangement of 4-(4′-aryloxybut-2′-ynylthio)-1-phenyl-1,8-naphthyridin-2(1H)-one

Majumdar¹,

Islam²

2006

Can. J. Chem.

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A number of 4-aryloxymethyl-6-phenyl-2H-thiopyrano[3,2-c] [1,8]naphthyridin-5(6H)-ones were regioselectively synthesized in 82%-95% yields by the thermal Claisen rearrangement of 4-(4′-aryloxybut-2′-ynylthio)-1-phenyl-[1,8]naphthyridin-2(1H)-ones. These products were then subjected to a second Claisen rearrangement in the presence of a Lewis acid catalyst, anhyd. AlCl 3 , to give hitherto unreported pentacyclic heterocycles in 75%-90% yields. The same final products were also obtained in low yield upon refluxing 4-aryloxymethyl-6-phenyl-2H-thiopyrano-[3,2-c] [1,8]naphthyridin-5(6H)-ones in N,N-diethyl aniline for 12-14 h. This method was found to be more effective than thermal Claisen rearrangement.Résumé : On a réalisé des synthèses régiosélectives de 4-aryloxyméthyl-6-phényl-2H-thiopyrano[3,2-c][1,8]naphtyridin-5(6H)-ones, avec des rendements allant de 82 % à 95 %, en soumettant des 4-(4'-aryloxybut-2'-ynylthio)-1-phényl[1,8]naphtyridin-2(1H)-ones à un réarrangement de Claisen thermique. Ces produits ont ensuite été soumis à un deuxième réar-rangement de Claisen, en présence d'un acide de Lewis comme catalyseur, le trichlorure d'aluminium, pour conduire à la formation d'hétérocycles pentacycliques non rapportés jusqu'à maintenant, avec des rendements allant de 75 % à 90 %. On a aussi obtenu ces produits avec de faibles rendements en portant les 4-aryloxyméthyl-6-phényl-2H-thiopyrano[3,2-c] [1,8]naphtyridin-5(6H)-ones au reflux dans la N,N-diéthylaniline pendant 12 à 14 h. On a trouvé que cette méthode est plus efficace que le réarrangement thermique de Claisen.Mots clés : réarrangement sigmatropique [3,3], synthèse régiosélective, catalyse par transfert de phase, réarrangements de Claisen séquentiels, réarrangement de Claisen catalysé par un acide de Lewis, diffraction des rayons X par un cristal unique.[Traduit par la Rédaction] Majumdar and Islam 1639

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“…In a continuing effort to exploit this novel finding to obtain other heterocycles, Majumdar and Thyagarajan 14,18 described an extension of their finding to nitrogen analogues for construction of the five-membered pyrrole ring of 2,3-disubstituted indoles. 39 It is relevant to mention that both the sulfoxide and amine oxide rearrangements proceed through the occurrence of concomitant [ Whilst the sulfoxides rearrange in refluxing carbon tetrachloride or dichloromethane, the corresponding rearrangement of the amine oxides occurs more readily, and the nitrogen heterocycles are obtained in almost quantitative yields.…”

Section: Amine Oxide Counterpart Of the Variantmentioning

confidence: 97%

“…14 The rearrangement occurs under relatively mild conditions, even at room temperature. The reaction time can be shortened by conducting the reaction in refluxing carbon tetrachloride.…”

Section: The New Variantmentioning

confidence: 99%

New Variation of the Aromatic ortho-Claisen Rearrangement: Synthesis of Fused Thiophenes and Pyrroles

Majumdar¹

2008

Synlett

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The development of a new variation of the aromatic ortho-Claisen rearrangement of aryl propargyl sulfoxides and arylpropargylamine oxides involving tandem [2,3]-and [3,3]-sigmatropic rearrangements followed by ketolization/S N 2¢ displacement to give fused thiophenes and pyrroles, respectively, is described. 1 Introduction 2 The New Variant 3 Mechanism 4 Applications 4.1 Synthesis of Condensed Thiophenes 4.2 Synthesis of Bioactive Heterocycle-Annulated Thiophenes 4.3 Unusual Dehydrogenative Elimination 4.4 Aliphatic Counterpart of the Variant 5 Amine Oxide Counterpart of the Variant 6 Conclusion

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Unusual ortho-Claisen rearrangements of aryl prop-2-ynyl sulphoxides

Cited by 30 publications

References 0 publications

Unexpected new examples of the Thyagarajan-Majumdar tandem cyclization of aryl propargyl sulfoxides

Unexpected new examples of the Thyagarajan-Majumdar tandem cyclization of aryl propargyl sulfoxides

Regioselective synthesis of biologically interesting pentacyclic polyheterocycles by sequential thio-Claisen and AlCl₃ catalyzed oxy-Claisen rearrangement of 4-(4′-aryloxybut-2′-ynylthio)-1-phenyl-1,8-naphthyridin-2(1H)-one

New Variation of the Aromatic ortho-Claisen Rearrangement: Synthesis of Fused Thiophenes and Pyrroles

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Unusual ortho-Claisen rearrangements of aryl prop-2-ynyl sulphoxides

Cited by 30 publications

References 0 publications

Unexpected new examples of the Thyagarajan-Majumdar tandem cyclization of aryl propargyl sulfoxides

Unexpected new examples of the Thyagarajan-Majumdar tandem cyclization of aryl propargyl sulfoxides

Regioselective synthesis of biologically interesting pentacyclic polyheterocycles by sequential thio-Claisen and AlCl3 catalyzed oxy-Claisen rearrangement of 4-(4′-aryloxybut-2′-ynylthio)-1-phenyl-1,8-naphthyridin-2(1H)-one

New Variation of the Aromatic ortho-Claisen Rearrangement: Synthesis of Fused Thiophenes and Pyrroles

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Regioselective synthesis of biologically interesting pentacyclic polyheterocycles by sequential thio-Claisen and AlCl₃ catalyzed oxy-Claisen rearrangement of 4-(4′-aryloxybut-2′-ynylthio)-1-phenyl-1,8-naphthyridin-2(1H)-one