Β-keto Sulfoxides Research Articles

Visible-light heterogeneous photocatalysis with an ionic porous organic polymer (IPOP): synthesis of β-keto sulfoxides and benzothiophene diesters by tandem radical addition–oxidation reactions

An IPOP, constructed constructed from cyanuric chloride and the readily accessible 2,5-di(pyridin-4-yl)thiazolo[5,4-d]thiazole (BpyTzTz), is shown to exhibit excellent visible light absorption and serve as a metal-free heterogeneous photocatalyst.

Tf2O-Mediated Direct Synthesis of 4-Sulfenylated Oxazoles from β-Keto Sulfoxides and Nitriles.

A general and efficient method for the synthesis of 4-sulfenylated oxazoles is described. Trisubstituted oxazoles are obtained in good to excellent yields from β-keto sulfoxides and nitriles. The mechanistic study suggests that the reaction proceeds via the nucleophilic addition of nitriles to the in situ formed α-carbonyl cation followed by intramolecular cyclization.

Photocatalytic functionalizations of alkynes.

Visible light mediated functionalizations have significantly expanded the scope of alkynes by unraveling new mechanistic pathways and enabling their transformation to diverse structural entities. The photoredox reactions on alkynes rely on their innate capability to generate myriad carbon-centred radicals via single electron transfer (SET), thereby, allowing the introduction of new radical precursors. Moreover, an array of methods have been developed facilitating transformations such as vicinal or gem-difunctionalization, annulation, cycloaddition and oxidative reactions to construct numerous key building blocks of natural and pharmaceutically important molecules. In addition, the introduction of photoredox chemistry has successfully been used to deal with the challenges associated with alkyne functionalization such as stereoselective and regioselective control. This article accounts for several visible light mediated functionalization reactions of alkynes, wherein they have been transformed into α-oxo compounds, β-keto sulfoxides, substituted olefins, N-heterocycles, internal alkynes and sulfur containing compounds. The article has been primarily categorized into various sections based on the reaction type with particular attention being paid to mechanistic details, advancement and future applications.

Recent Applications in the Use of Sulfoxides as Chiral Auxiliaries for the Asymmetric Synthesis of Natural and Biologically Active Products

The contribution of chiral sulfoxides as versatile auxiliaries in the field of organic chemistry has shown a prevalent interest in the asymmetric synthesis of natural products during the last 45 years. In this short review, we report the recent applications of these chiral auxiliaries to the synthesis of natural and biological active products highlighted from 2010 to 2019. We hope to allow the reader to have an overview of the potential of sulfoxide chemistry in the field of enantio­selective synthesis.1 Introduction2 Diastereoselective Additions to Ketones2.1 Reduction of β-Keto Sulfoxides2.2 Reduction of β-Keto Sulfoxides Followed by Bromohydrin Forma tion3 Synthesis of an α-Amino α′-Sulfinyl Ketone Followed by Diastere oselective Reduction of the β-Keto Sulfoxide4 Diastereoselective Addition of Carbanionic Chiral Sulfoxides4.1 Addition to an Aldehyde4.1.1 Aldol Reactions4.1.2 Reformatsky-Type Reactions4.2 Additions to Chiral Sulfinimines5 Diastereoselective Cyclization Reactions Directed by a Chiral Sulf oxide5.1 1,4-Radical Additions5.2 Intramolecular Conjugate Additions5.3 Nazarov Cyclizations5.4 Diels–Alder Reactions6 Atropodiastereoselective Synthesis7 Conclusion

Stereochemical analysis of β-keto sulfoxides by circular dichroism.

Three β-keto sulfoxides (1-3) were synthesized in enantiopure form and investigated by means of circular dichroism (CD) spectroscopy, both in electronic and vibrational range (ECD, VCD), in combination with quantum chemical calculations. For compound 2, the X-ray structure was available; thus, the ECD in the solid state was also considered to reveal the differences between the molecular species in both states. Despite the simplicity of all β-keto sulfoxides under investigation (29 atoms), reproducing even the major spectral VCD features failed for two compounds, making the use of VCD not ideal to assign their absolute configuration in a reliable way. We demonstrated, however, that the use of ECD spectroscopy, both in solution and solid state, can easily, unambiguously, and without any complication simulate all bands by applying the standard protocol for calculations. This study may stimulate the debate on the need of the use of two chiroptical methods simultaneously in the determination of absolute configurations.

Synthesis of Cyclic α-Diazo-β-keto Sulfoxides in Batch and Continuous Flow.

Diazo transfer to β-keto sulfoxides to form stable isolable α-diazo-β-keto sulfoxides has been achieved for the first time. Both monocyclic and benzofused ketone derived β-keto sulfoxides were successfully explored as substrates for diazo transfer. Use of continuous flow leads to isolation of the desired compounds in enhanced yields relative to standard batch conditions, with short reaction times, increased safety profile, and potential to scale up.

ChemInform Abstract: 1,3-Asymmetric Induction in the Reduction of α-Alkyl β-Keto Sulfoxides with DIBAL/ZnBr2.

ChemInform Abstract: 1,3-Asymmetric Induction in the Reduction of α-Alkyl β-Keto Sulfoxides with DIBAL/ZnBr2.

ChemInform Abstract: Novel Transformation of β-Keto Sulfoxides to Unsaturated β- Keto Sulfides.

Reaction of β-keto sulfoxides with trimethylsilyl trifluoromethanesulfonate in the presence of diisopropylethylamine afforded the corresponding (1E,3E)-1-phenylthio-2-(trimethylsilyloxy)-1,3-diene derivatives which underwent hydrolysis to furnish 1-phenylthio-alk-3-en-2-one derivatives in high yields.

ChemInform Abstract: Highly Diastereoselective Methylene Transfer from Diazomethane to the Carbonyl of β-Keto Sulfoxides. A General Approach to Synthetically Versatile Fluorine-Containing Chiral Building Blocks.

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First Synthesis of β-Keto Sulfoxides by a Palladium-Catalyzed Carbonylative Suzuki Reaction

[reaction: see text] An unprecedented palladium-catalyzed three-component cross-coupling reaction between alpha-bromo sulfoxide, carbon monoxide, and aromatic boronic acids provides a new and efficient approach to the synthesis of beta-ketosulfoxides. The reaction takes place under mild conditions with a wide range of variously substituted aryl and heteroaryl boronic acids. The carbonylative cross-coupling reaction is strongly favored over competing direct cross-coupling and homocoupling processes, except with boronic acids carrying strong electron-withdrawing substituents.

Highly Enantiomeric Purity Conversion of α-Sulfinyl Oximes and α-sulfinyl Hydrazones to the Corresponding β-keto Sulfoxides with Butyltriphenylphosphonium Periodate (BUTPPPI)

Butyltriphenylphosphonium periodate (Ph3P+BuIO4 −) 1 is readily prepared as a white solid from butyltriphenylphosphonium chloride, performs conversion of α-sulfinyl oximes (2) and α-sulfinyl hydrazones (4) to the corresponding β-keto sulfoxides (3) in high yields and high enantiomeric purity.

Synthesis of enantiomerically pure 2-amino alcohols from amino acids mediated by sulfoxides

Enantiomerically pure ( R 1, S 2)- and ( S 1, S 2)-2-amino alcohols can be easily synthesized by stereodivergent reduction of α′-( N-Boc)amino β-keto sulfoxides (easily synthesized from readily available N-Boc amino ester hydrochlorides) with DIBAH ( de 82–92%) and DIBAH/ZnBr 2 ( de 80%), followed by hydrogenolysis of the C–S bond of the resulting hydroxy sulfoxides and final hydrolysis of the N-Boc protecting group.

BENZYLTRIPHENYLPHOSPHONIUM PEROXODISULFATE (PhCH2PPh3)2S2O8: A MILD AND INEXPENSIVE REAGENT FOR HIGHLY ENANTIOMERIC PURITY OF α-SULFINYL OXIMES AND α-SULFINYL HYDRAZONES TO THE CORRESPONDING β-KETO SULFOXIDES

Benzyltriphenylphosphoniumperoxodisulfate (PhCH2PPh3)2S2O, (I) is readily prepared as an white solid from benzyltriphenylphosphoniumchloride, performs conversion of α-sulfinyl oximes (2) and α-sulfinyl hydrazones (4) to the corresponding β-keto sulfoxides (3) in high yields and high enantiomeric purity.

Chiral Ruthenium-Catalyzed Hydrogenation of β-Keto Sulfoxides

Chiral Ruthenium-Catalyzed Hydrogenation of β-Keto Sulfoxides

Chiral Ruthenium-Catalyzed Hydrogenation of β-Keto Sulfoxides

Chiral Ruthenium-Catalyzed Hydrogenation of β-Keto Sulfoxides

REACTIONS OF β-KETO SULFOXIDES WITH SULFUR ELECTROPHILES. PART II. STEREOCHEMICAL AND CONFIGURATIONAL STUDIES OF THE INTERMEDIATE ENOLATES

Some β-keto sulfoxides containing different groups at the sulfinyl moiety were submitted to sulfenylation reaction employing two procedures: in homogeneous media and by PTC to give the corresponding monosulfenylated products. The Z configuration for the enolates of the β-keto sulfoxides independently of the group at the sulfur moiety is proved by 1H NMR NOE difference experiments. The diastereoselectivity observed in the case of a t-butyl sulfinyl derivative is rationalized by preferred attack of the sulfur electrophile to the unhindered face of enolate not shielded by t-butyl group, as shown by X-ray analysis of the corresponding enol ether.

Sulfenylation of β-keto sulfoxides. III. Diastereoselectivity induced by a chiral phase transfer catalyst

The asymmetric induction in the sulfenylation of several β-keto sulfoxides under phase transfer catalytic conditions in the presence of the chiral catalyst N-benzylquininium chloride was investigated. It is concluded that the diastereoselectivity is not accompanied by enantiomeric resolution.

A facile stereospecific synthesis of chiral β-keto sulfoxides

A synthetic strategy has been devised for the preparation of chiral β-keto sulfoxides (actually, α-vinylsulfinyl ketones) starting from the readily available C-6 substituted 2,3-dihydro-1,4-oxathiines. The procedure, which is characterized by high yields and excellent enantiomeric excesses, represents an improvement in preparation methods for chiral β-keto sulfoxides.

Asymmetric synthesis of α-acetylenic epoxides

Chiral α-acetylenic oxiranes were easily synthesized from readily available propargylic esters by a four-step sequence involving the stereoselective reduction of α′-alkynyl β-keto sulfoxides with DIBAH ( de 66–78%) and DIBAH/ZnBr 2 ( de 78–88%), followed by further reduction of the resulting hydroxy sulfoxides into the corresponding sulfenyl derivatives and final epoxy ring closure via sulfonium salt.

Highly Enantiopure (tert-Butyldiphenylsilyloxymethyl)Oxiranes from Barium Carbonate

The synthesis of (2R)-(tert-butyldiphenylsilyloxymethyl)oxirane and the (2S)-enantiomer from barium carbonate was developed. Methyl glycolate or the hydroxamate analog was prepared and in turn reacted with (S)-(-)-methyl p-tolylsulfoxide or the (R)-enantiomer to make β-keto sulfoxides. From the sulfoxides, we made the diastereoisomeric alcohols in a highly selective sulfoxide group directed hydride reduction, and a Pummerer rearrangement reaction followed by deprotection yielded the enantiomeric diols. (2R)-(tert-Butyldiphenylsilyloxymethyl)oxirane and its (2S)-enantiomer were derived from these diols in an overall yield of 56% from barium carbonate. This method was developed to provide a convenient access to isotope-labeled analogs of these compounds.