Acid-Catalyzed Regioselective Sulfetherification of Alkenols and Stereoselective Rearrangement of Tetrahydrofuran to Tetrahydropyran

Synthesis of β-Hydroxysulfides via Multi-Component Cascade Hydroxysulfenylation of Styrenes with NH4 SCN and Water under Transition-metal-free Conditions

Transition-mental-free multi-component hydroxysulfenylation of styrenes with NH4 SCN and water to from β-hydroxysulfides is established. The reaction mechanism proceeded via a domino reaction after a radical addition to 2-phenylimidazo[1,2-a]pyridines. This approach features a wide substrate scope and functional group compatibility, providing 34 compounds in acceptable yields.

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

In the field of organosulfur chemistry, sulfenylating agents are an important key in C-S bond formation strategies. Among various organosulfur precursors, N-sulfenylsuccinimide/phthalimide derivatives have shown highly electrophilic reactivity for the asymmetric synthesis of many organic compounds. Hence, in this review article, we focus on the application of these alternative sulfenylating reagents in organic transformations.

Bromine-Promoted One-Pot Furo[b]annulation and α-C(sp2)-Thiomethylation Cascade of (E)-3-Styrylquinoxalin-2(1H)-ones with Dimethyl Sulfoxide

A new process has been developed for the bromine-promoted sequential (sp²)C = (sp²)C bond functionalization of (E)-3-styrylquinoxalin-2(1H)-ones and furo[b]annulation via the 5-exo-cyclization in dimethyl sulfoxide (DMSO). The reaction represents a novel strategy for the synthesis of 2-aryl-3-(methylthio)furo[2,3-b]quinoxalines and involves 3-(1,2-dibromo-2-arylethyl)quinoxalin-2(1H)-ones and 2-arylfuro[2,3-b]quinoxalines as key intermediates. Furthermore, DMSO was converted to dimethyl sulfide in situ, which served as the methylthiolation reagent in the reaction. This protocol constitutes an efficient and convenient method for the annulation and methylthiolation of (E)-3-styrylquinoxalin-2(1H)-ones bearing a wide range of functional groups in high yields at room temperature.

Asymmetric Halocyclizations of 2-Vinylbenzyl Alcohols with Chiral FLPs

By the use of a chiral frustrated Lewis pair (FLP) consisting of a chiral-diene-derived borane and ^tBu₃P as the catalyst, an asymmetric halocyclization of 2-vinylbenzyl alcohols with NBS or NIS was successfully realized. A variety of optically active 1,3-dihydroisobenofuran derivatives were obtained in high yields with up to 87% ee and could be conveniently converted to other useful chiral compounds.

Alkoxysulfenylation of alkenes: development and recent advances

Among the wide variety of synthetic transformations of inexpensive and abundant feedstock alkenes, vicinal difunctionalization of carbon-carbon double bonds represent one of the most powerful and effective strategies for the introduction of two distinct functional groups into target compounds in a one-pot process. In this context, the direct alkoxysulfenylation of alkenes has emerged as an elegant method to construct valuable β-alkoxy sulfides in an atom- and pot-economic manner utilizing readily accessible starting materials. Here, we review the available literature on this appealing research topic by hoping that it will be beneficial for eliciting further research and thinking in this domain.

Light-Promoted and Tertiary-Amine-Assisted Hydroxysulfenylation of Alkenes: Selective and Direct One-Pot Synthesis of β-Hydroxysulfides

A light-promoted and tertiary-amine-assisted strategy for efficient hydroxysulfenylation of both electron-rich and electron-deficient alkenes with thiophenols to selectively and directly access β-hydroxysulfides in one pot is described herein. In contrast to the previously reported thiol-oxygen co-oxidation reactions, this simple and sustainable approach features mild reaction conditions, high efficiency, and excellent functional group tolerance.

Selective oxidative intermolecular carbosulphenylation of aryl alkenes with thiols and nucleophiles via a 1,2-dithioethane intermediate

A periodate lithium-oxidized difunctionalisation of aryl alkenes with thiols and electron-rich aromatics was achieved, selectively affording more than thirty carbosulphenylated products. Both experiments and quantum chemical calculations demonstrated the radical-polar nature of the processes, and that 1,2-dithioethane and thiiranium ions might play the role of intermediates.

Lewis Base/Brønsted Acid Co-Catalyzed Asymmetric Thiolation of Alkenes with Acid-Controlled Divergent Regioselectivity

A divergent strategy for the facile preparation of various enantioenriched phenylthio-substituted lactones was developed based on Lewis base/Brønsted acid co-catalyzed thiolation of homoallylic acids. The acid-controlled regiodivergent cyclization (6-endo vs. 5-exo) and acid-mediated stereoselective rearrangement of phenylthio-substituted lactones were explored. Experimental and computational studies were performed to clarify the origins of the regioselectivity and enantioselectivity. The calculation results suggest that C-O and C-S bond formation might occur simultaneously, without formation of a commonly supposed catalyst-coordinated thiiranium ion intermediate and the potential π-π stacking between substrate and SPh as an important factor in the enantio-determining step. Finally, this methodology was applied in the rapid syntheses of the bioactive natural products (+)-ricciocarpin A and (R)-dodecan-4-olide.

Lewis base-catalyzed asymmetric sulfenylation of alkenes: construction of sulfenylated lactones and application to the formal syntheses of (-)-nicotlactone B and (-)-galbacin

An efficient method for the preparation of chiral sulfenylated lactones has been described based on Lewis base-catalyzed enantioselective sulfenylation of unsaturated carboxylic acids. The scope of this method includes two enantioselective cyclization reactions: 5-endo and 6-exo thiolactonizations of alkenes. Two types of lactones were obtained with up to 95% ee and 99% yield. Additionally, this methodology has been applied in the formal syntheses of bioactive natural products (-)-nicotlactone B and (-)-galbacin.

TMSCl-Catalyzed Electrophilic Thiocyano Oxyfunctionalization of Alkenes Using N-Thiocyano-dibenzenesulfonimide

Numerous electrophilic thiocyano oxyfunctionalization reactions of alkenes have been achieved using N-thiocyano-dibenzenesulfonimide, which is a new electrophilic thiocyanation reagent and could be easily prepared in two steps from dibenzenesulfonimide. This approach provides efficient, simple, and modular methods for the formation of SCN-containing heterocycles such as lactones, tetrahydrofurans, dihydrofurans, and dihydrobenzofurans in moderate to excellent yields. Meanwhile, diverse oxa-quaternary centers were rapidly constructed. Additionally, this protocol is free of transition metals and features broad substrate toleraance and mild reaction conditions.

Three-component difluoroalkylation–thiolation of alkenes by iron-facilitated visible-light photoredox catalysis

The first difluoroalkylation–thiolation of alkenes catalyzed by iron-facilitated photoredox has been developed with a broad substrate scope under mild conditions.

FeCl3-Catalyzed Regio-Divergent Carbosulfenylation of Unactivated Alkenes: Construction of a Medium-Sized Ring

A FeCl₃-catalyzed regio-divergent carbosulfenylation of unactivated alkenes with electrophilic N-sulfenophthalimides has been developed. This protocol provides a straightforward and efficient access to various medium-sized rings, especially strained 7- and 8-membered carborings with a sulfur atom attached. The endo/exo selectivity in the reaction depends on the atom number of the chain between arene and alkene. Broad substrate scope, high yields, and gram-scale synthesis exemplified the utility and practicability of this protocol. In addition, this methodology can be extended to the carboselenylation of isolated alkenes.

Hydrochloric Acid-Promoted Intermolecular 1,2-Thiofunctionalization of Aromatic Alkenes

An efficient method for making 1,2-thiofunctionalized products via the difunctionalization of aromatic alkenes was developed. In this method, cheap and readily available hydrochloric acid was used to promote 1,2-thiofunctionalization of aryl alkenes with N-arylsulfenylphthalimide and different types of nucleophiles. Importantly, extension of nucleophiles can reach aryl ethers, indoles, and carboxylic acids with good reactivity. This practical and convenient method has broad substrate scope and high yields under metal-free and mild conditions. Furthermore, we achieved conversion and application for making sulfoxide and sulfone by oxidation.

Copper-catalyzed regioselective 1,2-thioamidation of alkenes

An efficient method for regioselective 1,2-thioamidation of terminal alkenes, catalyzed by copper in the presence of NFSI and thiols, has been disclosed.

N-Heterocyclic Carbene Catalyzed Sulfenylation of α,β-Unsaturated Aldehydes

An efficient N-heterocyclic carbene (NHC) catalyzed sulfenylation reaction of α,β-unsaturated aldehydes with N-(arylthio)phthalimide has been developed. A wide variety of α-thioenals can be obtained with good to excellent yields and excellent Z-configuration.

Brønsted acid-catalyzed chemodivergent reactions of ortho-mercaptobenzyl alcohols with 3-alkyl-2-vinylindoles and styrenes: [5+2] cyclization versus hydroxysulfenylation

The title reactions were established to provide efficient methods for constructing a benzoxathiepine scaffold and synthesizing β-hydroxy sulfides in good yield and excellent diastereoselectivity.

Highly selective synthesis of 6-substituted benzothiophenes by Sc(OTf)3-catalyzed intermolecular cyclization and sulfur migration

A series of 6-substituted benzo[b]thiophenes was synthesized using a Sc(OTf)₃-catalyzed intermolecular cyclization between para-substituted N-(arylthio)succinimides and alkynes taking advantage of a unique and selective 1,2-sulfur migration occuring via an electrophilic ipso cyclization to a key spirocyclic thiete intermediate.

Metal-free oxysulfenylation of alkenes with 1-(arylthio)pyrrolidine-2,5-diones and alcohols

An easy and efficient metal-free approach to β-alkoxy sulfides has been developed. The protocol uses readily available 1-(arylthio)pyrrolidine-2,5-diones and alcohols as the oxysulfenylating agents, chloroform as the solvent, and no ligand, additive and exclusion of air were required.

Silver-catalyzed direct spirocyclization of alkynes with thiophenols: a simple and facile approach to 3-thioazaspiro[4,5]trienones

A convenient and efficient silver-catalyzed direct oxidative spirocyclization of alkynes with thiophenols leading to 3-thioazaspiro[4,5]trienones has been developed under air.

Enantioselective bromoaminocyclization of allyl N-tosylcarbamates catalyzed by a chiral phosphine-Sc(OTf)3 complex

An effective enantioselective bromoaminocyclization of allyl N-tosylcarbamates catalyzed by a chiral phosphine-Sc(OTf)3 complex is described. A wide variety of optically active oxazolidinone derivatives containing various functional groups can be obtained with high enantioselectivities.

Enantioselective bromocyclization of olefins catalyzed by chiral phosphoric acid

A chiral phosphoric acid catalyzed enantioselective bromocyclization of olefins is described. Various cis-, trans-, or trisubstituted γ-hydroxy-alkenes and γ-amino-alkenes can cyclize under the reaction conditions to give optically active 2-substituted tetrahydrofurans and tetrahydropyrroles in up to 91% ee.

Catalytic asymmetric thiofunctionalization of unactivated alkenes

Catalytic asymmetric sulfenylation of double bonds has been achieved using a BINAM-based phosphoramide catalyst and an electrophilic sulfur source. Simple alkenes as well as styrenes afforded sulfenylated tetrahydrofurans and tetrahydropyrans by closure with pendant hydroxyl or carboxyl groups. Intermolecular thiofunctionalizations were also achieved with simple alcohols or carboxylic acids as the nucleophiles.