α-Sulfanyl and α-Selanyl Propadienyl Cations: Regioselective Generations and Cycloadditions with Thioamides and Selemides Controlled by MeNO<sub>2</sub>−H<sub>2</sub>O System

Yoshimatsu, Mitsuhiro; Yamamoto, T.; Sawa, Arisa; Kato, Tomohiro; Tanabe, Genzoh; Muraoka, Osamu

doi:10.1021/ol9011844

Cited by 55 publications

(25 citation statements)

References 21 publications

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“…Following previously proposed mechanisms for homogeneous acid catalysts17j–l and the above experiments in which the intermediate carbocation was detected, Scheme shows what could be a general mechanism for the nucleophilic addition to propargyl alcohols with a zeolite catalyst. The first step is the formation of the carbocation on the acid sites, followed by nucleophilic attack and cyclization.…”

Section: Methodsmentioning

confidence: 71%

Beyond Acid Strength in Zeolites: Soft Framework Counteranions for Stabilization of Carbocations on Zeolites and Its Implication in Organic Synthesis

2015

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The generation of a carbocation with an acid depends not only on the acid strength but also on the ability of the counteranion to stabilize the positive charge left behind. Here we report that despite their relatively weak acidity, zeolites are able to generate and stabilize medium‐size (molecular weight ≈300 Da) delocalized carbocations on their surface under mild reaction conditions, as it can be done by strong Brønsted or Lewis acids in solution. The zeolite thus acts as a soft macroanion, prolonging the lifetime of the carbocation sufficiently to perform multifunctionalization reactions with amides, thioamides, and phenols, with high yield and selectivity. Biological studies show that some of the products obtained here present significant inhibition activity against colon cancer cells, illustrating the new possibilities of zeolites to prepare complex organic molecules.

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Section: Methodsmentioning

confidence: 71%

Beyond Acid Strength in Zeolites: Soft Framework Counteranions for Stabilization of Carbocations on Zeolites and Its Implication in Organic Synthesis

2015

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“…[40][41][42][43] Scandium-catalyzed etherifications in nitromethane resulted in a complex mixture; however, the addition of H 2 O drastically improved the reaction and provided ether 3a in 84% yield (entries 1 and 2). and 5).…”

Section: Resultsmentioning

confidence: 99%

Lewis Acid-Catalyzed Propargylic Etherification and Sulfanylation from Alcohols in MeNO2-H2O

Ohta

Koketsu

Nagase

et al. 2011

CHEMICAL & PHARMACEUTICAL BULLETIN

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Results of screening of other etherification conditions using 1a are shown in Table 1. Various metals, mainly lanthanoids, were found to be effective for etherifications in MeNO 2 -H 2 O. Next, we selected propargyl alcohols bearing other aromatic substituents as starting materials and performed etherifications under the suitable condition using Sc(OTf) 3 /MeNO 2 -H 2 O at 30°C. With the Sn(OTf) 2 system, the product 2aa was also obtained in the satisfactory yield, however, a small amount of unknown compounds were contaminated. Results of these comparisons are shown in Table 1.Using the same substrate, 3-p-methoxyphenylpropargyl alcohol 1a, etherification with 1°alcohols including methanol, dodecanol and geraniol as nucleophiles produced products 2ab, 2ac and 2af, respectively, in good yields (entries 1, 2

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“…A subsequent nucleophilic attack of amide 5-119 would produce intermediate 5-124 , which undergoes a Sc(III)-catalyzed cycloisomerization into a cyclic intermediate 5-125 , finally producing the coresponding aromatic heterocycle 5-121 upon tautomerization (Scheme 360). 568 …”

Section: Synthesis Of 5-membered Heterocycles With Two or More Hetmentioning

confidence: 99%

Transition Metal-Mediated Synthesis of Monocyclic Aromatic Heterocycles

et al. 2013

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α-Sulfanyl and α-Selanyl Propadienyl Cations: Regioselective Generations and Cycloadditions with Thioamides and Selemides Controlled by MeNO₂−H₂O System

Abstract: Alpha-sulfanyl and alpha-selanyl propadienyl cations were easily generated by the catalytic system, scandium triflate-nitromethane-H(2)O in the presence of Bu(4)NHSO(4), to regioselectively afford the multifunctionalized thiazoles and selenazoles in high yields.

Cited by 55 publications

References 21 publications

Beyond Acid Strength in Zeolites: Soft Framework Counteranions for Stabilization of Carbocations on Zeolites and Its Implication in Organic Synthesis

Beyond Acid Strength in Zeolites: Soft Framework Counteranions for Stabilization of Carbocations on Zeolites and Its Implication in Organic Synthesis

Lewis Acid-Catalyzed Propargylic Etherification and Sulfanylation from Alcohols in MeNO2-H2O

Transition Metal-Mediated Synthesis of Monocyclic Aromatic Heterocycles

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α-Sulfanyl and α-Selanyl Propadienyl Cations: Regioselective Generations and Cycloadditions with Thioamides and Selemides Controlled by MeNO2−H2O System

Abstract: Alpha-sulfanyl and alpha-selanyl propadienyl cations were easily generated by the catalytic system, scandium triflate-nitromethane-H(2)O in the presence of Bu(4)NHSO(4), to regioselectively afford the multifunctionalized thiazoles and selenazoles in high yields.

Cited by 55 publications

References 21 publications

Beyond Acid Strength in Zeolites: Soft Framework Counteranions for Stabilization of Carbocations on Zeolites and Its Implication in Organic Synthesis

Beyond Acid Strength in Zeolites: Soft Framework Counteranions for Stabilization of Carbocations on Zeolites and Its Implication in Organic Synthesis

Lewis Acid-Catalyzed Propargylic Etherification and Sulfanylation from Alcohols in MeNO2-H2O

Transition Metal-Mediated Synthesis of Monocyclic Aromatic Heterocycles

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α-Sulfanyl and α-Selanyl Propadienyl Cations: Regioselective Generations and Cycloadditions with Thioamides and Selemides Controlled by MeNO₂−H₂O System