Synthesis Of Oxazolines Research Articles

Organocatalytic asymmetric synthesis of oxazolines from N-acylimines

Organocatalytic asymmetric synthesis of oxazolines from N-acylimines

Convenient total synthesis of Bistratamides H and J

Scalable total syntheses of Bistratamides H and J with remarkable yields of 22.9 % and 24.2 % over 9 steps, respectively, have been accomplished. The key step features a PPh3-promoted cascade reaction (disulfide cleavage/thiocarbonylation/intramolecular Staudinger-aza-Wittig reaction/dehydrogenation) to construct the key Boc-l-Val-thiazole fragment, DAST-promoted oxazoline synthesis, and a PyBOP-assisted macrolactamization.

Palladium-catalyzed epoxidation of olefins using electrophiles as oxidizing agents

The development of palladium-catalysed olefin epoxidation reactions using electrophilic reagents as oxidants: modular synthesis of oxazolines. The efficient synthesis of esters, alcohols and halogen-containing products was achieved.

Synthesis of oxazolines through a Pd-catalyzed alkyne-enabled C[sbnd]N activation of oxazolidines

Strategies that enable selective CN bond activation of tertiary amines provide one of the cornerstones of modern organic synthesis. Here we describe a palladium-catalyzed selective CN bond cleavage of N-propargyl 1,3-oxazolidines, providing an efficient approach to a diverse range of oxazolines in good to excellent yields. The reaction proceeds through a domino process of the alkyne-enabled 1,5-hydrogen transfer/CN bond activation. In this way, two kinds of oxazoline skeleton that tolerates a wide variety of functional groups were formed.

Base‐catalyzed [3 + 2]/[4 + 2]‐annulations of cyclic N‐sulfimines with γ‐ and δ‐sulfonamido/hydroxy‐α,β‐unsaturated carbonyls: Stereoselective synthesis of imidazolidines, oxazolidines, hexahydropyrimidines, and 1,3‐oxazinanes

AbstractA highly efficient and straightforward synthetic methodology has been established for the preparation of imidazolidine derivatives through the [3 + 2]‐annulation of cyclic N‐sulfimines. This reaction involves the reaction of cyclic N‐sulfimines and γ‐sulfonamido‐α,β‐unsaturated carbonyl compounds, with Cs2CO3 serving as the catalyst. The outcome is a diverse range of imidazolidine derivatives with remarkable yields and stereoselectivities. In addition, the [4 + 2]‐annulation between cyclic N‐sulfimines and δ‐sulfonamido‐α,β‐unsaturated carbonyl compounds, catalyzed by Et3N, has been successfully applied for the synthesis of stereoselective hexahydropyrimidines. Furthermore, the base‐catalyzed annulation of cyclic N‐sulfimines with γ‐ and δ‐hydroxy‐α,β‐unsaturated carbonyl compounds has proven to be a reliable method for the synthesis of oxazolines and 1,3‐oxazinanes.

Development of a by-product-free strategy for the synthesis of oxazoline from N-acetylglucosamine

This study focused on the CDMBI-mediated synthesis of GlcNAc oxazoline.

Advancements in the synthesis of oxazolines

Advancements in the synthesis of oxazolines

Chloride-mediated electrochemical synthesis of oxazolines

In this issue of Chem Catalysis, Liang et al. report an efficient electrochemical cyclization reaction of alkenes and amides to produce oxazolines with broad substrate scopes and good selectivities. A chloronium species generated by the chloride-mediated redox catalysis is proposed as a key intermediate.

Visible-light-promoted radical alkylation/cyclization of allylic amide with N-hydroxyphthalimide ester: Synthesis of oxazolines

An efficient photocatalytic alkylation/cyclization of allylic amide with N-hydroxyphthalimide ester has been developed. The transformation is taken advantage of alkyl radicals to attack allylic amide with the assist of inexpensive rose bengal as photocatalyst to prepare a series of alkyl substituted oxazolines in moderate to excellent yields. High regioselectivity, operational safety, mild conditions and excellent substrate generality give this protocol broad application prospects.

Electrochemical (3 + 2) cyclization between amides and olefins

Amides and olefins are cheap and readily available industrial materials. Hence, the synthesis of oxazolines from amides and olefins is significant. Regio- and site-selective amino-oxygenation of olefins is one of the most desirable transformations for important oxazoline derivatives, which are common motifs in pharmaceuticals, natural products, agrochemicals, and chiral ligands. However, strong oxidants and iodine reagents create challenges for its applications in organic synthesis. Here, we demonstrate an electrochemical (3 + 2) cyclization between amides and olefins. Various oxazolines are delivered in good yields and with excellent site selectivity and diastereoselectivity simultaneously. Mechanistic studies indicate that chlorine anions, generated from inexpensive 1,2-dichloroethane by cathodic reduction, can be oxidized on the anode and react with alkenes to generate chloronium species, which are key intermediates for this electrochemical cyclization.

Asymmetric synthesis of oxazolines bearing α-stereocenters through radical addition–enantioselective protonation enabled by cooperative catalysis

An efficient radical conjugate addition/enantioselective protonation process was developed for the asymmetric synthesis of chiral oxazolines bearing an α-stereocenter through cooperative photoredox catalysis and asymmetric organocatalysis.

Kinetic Resolution of 2‐N‐Acylamido Tertiary Allylic Alcohols: Asymmetric Synthesis of Oxazolines

AbstractA series of cyclohexyl‐fused SPINOL‐derived phosphoric acids (Cy‐SPA) have been developed to catalyze the kinetic resolution of 2‐N‐acylamido tertiary allylic alcohols, providing access to chiral oxazolines bearing C‐2 alkyl substituents with high enantioselectivities (with s‐factors up to 153). Gram‐scale reaction with 1 mol% catalyst loading and transformations of the chiral products demonstrates the value of these methods.magnified image

Synthesis of Oxazoline and Oxazole Derivatives by Hypervalent-Iodine-Mediated Oxidative Cycloaddition Reactions

Organohypervalent iodine reagents are widely used for the preparation of various oxazolines, oxazoles, isoxazolines, and isoxazoles. In the formation of these heterocyclic compounds, hypervalent iodine species can serve as the activating reagents for various substrates, as well as the heteroatom donor reagents. In recent research, both chemical and electrochemical approaches toward generation of hypervalent iodine species have been utilized. The in situ generated active species can react with appropriate substrates to give the corresponding heterocyclic products. In this short review, we summarize the hypervalent-iodine­-mediated preparation of oxazolines, oxazoles, isoxazolines, and isoxazoles starting from various substrates.1 Introduction2 Synthesis of Oxazolines3 Synthesis of Oxazoles4 Synthesis of Isoxazolines5 Synthesis of Isoxazoles6 Conclusion

Improved Synthetic Method for 5-[(Phenylthio)methyl]oxazoline Derivatives: Electrophilic Cyclization of Allylic Amide Using a Brønsted Acid and Tetrabutylammonium Chloride under Mild Conditions

The synthesis of oxazolines using electrophilic cyclization of allylic amide is a simple and powerful method. However, cyclization involving arylsulfenylation requires harsh reaction conditions. We found that the reaction proceeds under mild heating conditions with the combination of a Brønsted acid and tetrabutylammonium chloride. This method enabled the synthesis of 5-[(arylsulfenyl)methyl]oxazoline derivatives under mild conditions and demonstrated high tolerance for various functional groups.

Copper-Catalyzed Enantioselective Synthesis of Oxazolines from Aminotriols via Asymmetric Desymmetrization.

A copper-catalyzed enantioselective transformation of tris(hydroxymethyl)aminomethane-derived aminotriols was developed to provide multisubstituted oxazolines with a tetrasubstituted carbon center. The present transformation consisted of sequential reactions involving mono-sulfonylation of aminotriols, subsequent intramolecular cyclization to afford prochiral oxazoline diols, and sulfonylative asymmetric desymmetrization of resultant oxazoline diols. In addition, the kinetic resolution process would be involved in the sulfonylative asymmetric desymmetrization step, which would amplify the enantiopurities of the desired products. Various aminotriols were tolerated in the present reaction, affording the desired oxazolines in good to high yields with excellent enantioselectivities. The synthetic utility of the present reaction was demonstrated by the transformation of the optically active oxazoline into a chiral α-tertiary amine motif.

Electrochemical Chalcogenation of β,γ‐Unsaturated Amides and Oximes to Corresponding Oxazolines and Isoxazolines

AbstractThe current report represents a transition‐metal‐free synthesis of oxazoline and isoxazoline derivatives by a tandem electro‐oxidative chalcogenation‐cyclization process. Both C−Se and C−S bond‐forming protocols were developed without using any external oxidant and the reaction was performed at room temperature, open to the air. Using this methodology, 29 substituted oxazoline and 16 substituted isoxazoline derivatives were synthesized with up to 91% isolated yield.magnified image

Oxazoline Synthesis by Using the XtalFluor-E Reagent

Key words oxazolines - amino alcohols - desilylation - cyclodehydration

Synthesis of oxazolines and oxazoles by the reaction of propynals with tosylmethyl isocyanide

The reaction of 3-(trimethylsilyl)propynal, 3-(triethylgermyl) propynal or 3-phenylpropynal with tosylmethyl isocyanide affords new 5-alkynyl-4-tosyl-2-oxazolines and/or 5-alkynyl-1,3-oxazoles.

XtalFluor‐E: An Efficient Reagent for Synthesis of Oxazolines from Carboxylic Acids and O‐Silylated Amino Alcohols

An efficient protocol has been developed for the synthesis of 2‐oxazolines from carboxylic acids and silylated amino alcohols. The advantage of this method was demonstrated by preparing O‐silylated amino alcohols. The reaction proceeds via in situ desilylation of O‐silylated amide followed by cyclization. Studies on silyl deprotection were carried out to explain yield for 2‐oxazolines.

Diastereoselective One-Pot Synthesis of Oxazolines Using Sulfur Ylides and Acyl Imines.

This work describes an extended version of the Corey-Chaykovsky reaction to access oxazolines using sulfur ylides and stable precursors of acyl imines. The reaction proceeds through a mixture of aziridines and oxazolines, which provides the trans-oxazolines following in situ Heine-type aziridine ring expansion upon treatment with BF3·OEt2. Following the same one-pot procedure, amidine imides react with the sulfur ylides to provide imidazolines.