Preparation of 2,4,5-Trisubstituted Oxazoles through Iodine-mediated Aerobic Oxidative Cyclization of Enaminones

Weng, Yunxiang; Lv, Weiwei; Yu, Jia; Ge, Bailu; Cheng, Guolin

doi:10.1021/acs.orglett.8b00376

Cited by 61 publications

(11 citation statements)

References 54 publications

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“…To test this ring-opening N-alkylation of 2-oxazoline, benzyl bromide (1a) and 2-methyl-2-oxazoline (2) were chosen as the model substrates for the reaction in the presence of 20 mol % of CuBr 2 , 2 equiv of KOt-Bu in CH 3 CN at 100 °C for 16 h, and a full conversion to the 2-aminoethyl acetate product 3a was obtained ( Table 1, entry 1). By changing the copper salt to CuBr or CuI, similar results were detected under the same conditions ( Table 1, entries 2 and 3).…”

Section: Resultsmentioning

confidence: 99%

“…2-Oxazolines are important structural units in pharmaceutical applications and efficient ligands in coordination chemistry, and also valuable protecting or directing groups in catalysis [1][2][3]. 2-Oxazolines are a readily stable class of heterocycles resistant to a range of nucleophiles, bases, or radicals [4,5], which can be easily generated from amino alcohols and carboxylic acids, and from alkenes or epoxides as substrates via alternative synthetic procedures [6].…”

Section: Introductionmentioning

confidence: 99%

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KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

Lin¹,

Zhang²,

Li³

2020

Beilstein J. Org. Chem.

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An efficient and simple KOt-Bu-promoted selective ring-opening N-alkylation of 2-methyl-2-oxazoline or 2-(methylthio)-4,5-dihydrothiazole with benzyl halides under basic conditions is described for the first time. The method provides a convenient and practical pathway for the synthesis of versatile 2-aminoethyl acetates and N-substituted thiazolidinones with good functional group tolerance and selectivity. KOt-Bu not only plays an important role to promote this ring-opening N-alkylation, but also acts as an oxygen donor.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

Lin¹,

Zhang²,

Li³

2020

Beilstein J. Org. Chem.

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“…Weng and colleagues [54] developed efficient and easy aerobic dehydrogenative, annulation of enaminone 69 a to synthesise oxazole 71 (Scheme 27). This methodology signifies the iodine‐mediated oxazole formation from enaminone under metal‐free condition.…”

Section: Literature Reviewmentioning

confidence: 99%

Recent Progress in Iodine‐Catalysed C−O/C−N Bond Formation of 1,3‐Oxazoles: A Comprehensive Review

et al. 2021

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Over the last few decades, iodine has been a stellar catalyst for numerous organic transformations such as CÀ H activation, hetero-annulation and coupling reactions. In heterocyclic chemistry, iodine is primarily an economical and eco-friendly catalyst that fascinates the construction of CÀ O/CÀ N bonds via oxidative, radical, and electrophilic pathways. Several novel Iodine-catalyzed methodologies have been reported, presenting advances in heterocyclic synthesis with regioselectivity, wide substrate scope and excellent yields. Furthermore, feasible protocols implemented to get oxazole annulation in literature have an enormous impact on new synthetic applications. Therefore, this literature analysis comprises advancements in the field of iodine-mediated 1,3-oxazole synthesis since 1998. For the ease of the readers, the reported methodologies have been categorised based on iodine functioning in reactions with insight into the reaction mechanisms and highlights.

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“…Enamine derivatives, including enaminones/enamine ester, − heterocyclic ketene aminals (HKAs), − and so on, are attractive and versatile building blocks for the synthesis of various heterocycles. Some have potentially useful biological activities, such as antitumor, antibacterial, antileishmanial, etc.…”

mentioning

confidence: 99%

Multicomponent Cascade Reaction of 3-Formylchromones: Highly Selective Synthesis of Functionalized 9-Azabicyclo[3.3.1]nonane Derivatives

Duan

Cao

et al. 2021

Org. Lett.

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A novel protocol for the preparation of functionalized 9-azabicyclo[3.3.1]nonane (ABCN) derivatives from 3formylchromones, enaminones, and heterocyclic ketene aminals (HKAs) through an unprecedented cascade reaction has been developed by simply refluxing the mixture of the substrates 1−3. As a result, a series of ABCNs were produced through a very complex cascade reaction. This protocol can be used in the synthesis of ABCNs that are suitable for combinatorial and parallel syntheses of ABCN natural-like products in a one-pot reaction.

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Preparation of 2,4,5-Trisubstituted Oxazoles through Iodine-mediated Aerobic Oxidative Cyclization of Enaminones

Abstract: A novel approach to trisubstituted oxazoles has been developed that is based upon an iodine-mediated aerobic oxidative cyclization of enaminone derivatives. This transition-metal-free procedure was highly efficient and involved the removal of four hydrogen atoms under mild conditions.

Cited by 61 publications

References 54 publications

KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

Recent Progress in Iodine‐Catalysed C−O/C−N Bond Formation of 1,3‐Oxazoles: A Comprehensive Review

Multicomponent Cascade Reaction of 3-Formylchromones: Highly Selective Synthesis of Functionalized 9-Azabicyclo[3.3.1]nonane Derivatives

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