Stevens rearrangement of thioethers with arynes: a facile access to multi-substituted β-keto thioethers

Investigation of thia-Diels-Alder Reactions by Ultrafast Transient Absorption Spectroscopy and DFT Calculations

The thia-Diels-Alder reaction represents a versatile synthetic method for the preparation of six-membered sulfur-containing compounds. However, the mechanism of the thia-Diels-Alder reactions remains unclear. In this work, time-resolved spectroscopic experiments and DFT calculations demonstrate that phenacyl sulfide undergoes Norrish II cleavage to produce thioaldehyde, and ortho-hydroxy benzhydryl alcohol occurs in a dehydration reaction to generate o-QMs using diphenylphosphate as the catalyst. Then, the thia-Diels-Alder reaction takes place between thioaldehyde and o-QMs by an asynchronous concerted mechanism. The illustration of the thia-Diels-Alder reaction mechanism not only provides important support for organic synthesis and drug design but also enhances fundamental insights into reaction pathways and catalytic processes in the field of chemical synthesis.

The perfluoroalkylthiolation/decarbonylation reaction of 1,3-diketones with perfluoroalkanesulfenic acids

The perfluoroalkylthiolation/decarbonylation reactions of 1,3-dicarbonyl compounds with in situ formed perfluoroalkanesulfenic acids were achieved. Using trifluoromethanesulfonic acid as an additive, a series of α-perfluoroalkylthiolated arylethanones were obtained in moderate to good yields. A possible mechanism was proposed based on the reaction results and control experiments.

Synthesis of Trisubstituted Oxazoles via Aryne Induced [2,3] Sigmatropic Rearrangement-Annulation Cascade

A transition-metal-free, [2,3] sigmatropic rearrangement-annulation cascade of 2-substituted thio/amino acetonitriles with arynes allowing the synthesis of 2,4,5-trisubstituted oxazoles under mild conditions has been demonstrated. The key sulfur/nitrogen ylides were generated by the initial S/N arylation followed by proton transfer, which was followed by the selective [2,3] sigmatropic rearrangement involving the -CN moiety and a subsequent annulation to afford the desired products in reasonable yields.

Enantioselective [1,2]-Stevens Rearrangement of Thiosulfonates to Construct Dithio-Substituted Quaternary Carbon Centers

An enantioselective [1,2] Stevens rearrangement was realized by using chiral guanidine and copper(i) complexes. Bis-sulfuration of α-diazocarbonyl compounds was developed through using thiosulfonates as the sulfenylating agent. It was undoubtedly an atom-economic process providing an efficient route to access novel chiral dithioketal derivatives, affording the corresponding products in good yields (up to 90% yield) and enantioselectivities (up to 96 : 4 er). A novel catalytic cycle was proposed to rationalize the reaction process and enantiocontrol.

An asymmetric [1,2] Stevens rearrangement was realized via chiral guanidine and copper(i) complexes. A series of novel chiral dithioketal derivatives were obtained with good yields (up to 90% yield) and enantioselectivities (up to 96 : 4 er).

A copper-catalyzed three-component reaction of dithioacetals with diazo ketones and ketimines

An efficient protocol for the synthesis of various acyclic thioacetal derivatives and medium-size sulfur-containing heterocycles via copper-catalyzed three-component reaction of dithioacetals with diazo-ketones and ketimines was reported.

Access to diverse organosulfur compounds via arynes: a comprehensive review on Kobayashi's aryne precursor

Arynes are highly reactive transient intermediates having enormous applications in organic synthesis. In the last three decades aryne chemistry has shown incredible developments in carbon-carbon and carbon-heteroatom bond formation reactions. After the discovery of Kobayashi's protocol for the generation of aryne intermediates in a mild way, this field of chemistry witnessed rapid growth in synthetic organic chemistry. One aspect of development in this field involves C-S bond formation under mild conditions which has a tremendous scope for the synthesis of various important organosulfur building blocks.

An Umpolung Oxa-[2,3] Sigmatropic Rearrangement Employing Arynes for the Synthesis of Functionalized Enol Ethers

An oxa-[2,3] sigmatropic rearrangement involving arynes is reported featuring the umpolung of ketones, where the C═O bond polarity is reversed. The in situ-generated sulfur ylides from β-keto thioethers and arynes undergo efficient rearrangement allowing the facile and robust synthesis of functionalized enol ethers in high yields and excellent functional group compatibility. Preliminary mechanistic studies rule out the possibility of Pummerer-type rearrangement operating in this case.

Selective synthesis of α-organylthio esters and α-organylthio ketones from β-keto esters and sodium S-organyl sulfurothioates under basic conditions

We described herein a selective method to prepare α-organylthio esters and α-organylthio ketones by the reaction of β-keto esters with sodium S-benzyl sulfurothioate or sodium S-alkyl sulfurothioate (Bunte salts) under basic conditions in toluene as the solvent at 100 °C. When 4 equivalents of a base were used, a series of differently substituted α-thio esters were obtained with up to 90% yield. On the other hand, employing 2 equivalents of a base, α-thio ketones were achieved after 18 h under air. Furthermore, after a shorter reaction time, the isolation of keto-enol tautomers was possible, revealing them as significant intermediates for the mechanism elucidation.

Construction of 6H-benzo[c]thiochromenes via a tandem reaction of arynes with thionoesters

A mild and transition-metal free method has been proposed for the synthesis of 6H-benzo[c]thiochromenes via the tandem reactions of arynes with thionoesters.

One-step synthesis of benzo[b]thiophenes by aryne reaction with alkynyl sulfides

An aryne reaction with alkynyl sulfides affording benzo[b]thiophenes is disclosed. A wide range of 3-substituted benzothiophenes were synthesized from easily available o-silylaryl triflates and alkynyl sulfides in a one-step intermolecular manner. The synthesis of diverse multisubstituted benzothiophene derivatives involving a pentacyclic compound was achieved by virtue of the good functional group tolerance and versatile C2 functionalizations.

Microwave assisted synthesis of β-keto thioethers and furan derivatives by thiol directed multicomponent reactions

A series of β-keto thioethers tethered with cyclic-1,3-dicarbonyls (4) and a tetra-substituted furan derivative (5) has been prepared by multicomponent reaction under microwave heating conditions.

Bond-Forming and -Breaking Reactions at Sulfur(IV): Sulfoxides, Sulfonium Salts, Sulfur Ylides, and Sulfinate Salts

Organosulfur compounds have long played a vital role in organic chemistry and in the development of novel chemical structures and architectures. Prominent among these organosulfur compounds are those involving a sulfur(IV) center, which have been the subject of countless investigations over more than a hundred years. In addition to a long list of textbook sulfur-based reactions, there has been a sustained interest in the chemistry of organosulfur(IV) compounds in recent years. Of particular interest within organosulfur chemistry is the ease with which the synthetic chemist can effect a wide range of transformations through either bond formation or bond cleavage at sulfur. This review aims to cover the developments of the past decade in the chemistry of organic sulfur(IV) molecules and provide insight into both the wide range of reactions which critically rely on this versatile element and the diverse scaffolds that can thereby be synthesized.

Transition-Metal-Free Thioamination of Arynes Using Sulfenamides

The insertion of arynes into the S-N σ-bond of sulfenamides allowing the synthesis of o-sulfanylaniline derivatives with reasonable functional group compatibility is presented. The aryne generated from 2-(trimethylsilyl)aryl triflates using CsF in DME was the key for the success of this transition-metal-free thioamination reaction, which involves new C-N and C-S bond formations in a single step under mild conditions. Moreover, the synthetic potential of this method was demonstrated by the synthesis of the antidepressant drug vortioxetine.

α-Thiocarbonyl synthesisviathe FeII-catalyzed insertion reaction of α-diazocarbonyls into S–H bonds

Fe(OTf)₂was used to catalyze the insertion reaction of α-diazocarbonyls into S–H bonds at 40 °C.

The aryne Sommelet–Hauser rearrangement

An aryne induced transition-metal-free and mild Sommelet–Hauser rearrangement of tertiary benzylamines for the synthesis of α-aryl amino acid derivatives in moderate to good yields and with broad substrate scope is presented.

An aryne triggered ring-opening fluorination of cyclic thioethers with potassium fluoride

Herein, we report an aryne triggered ring-opening fluorination protocol of a great variety of saturated sulfur heterocycles. A key factor for the success is the identification of a suitable mediator. Compared to previous methods, this transition-metal free protocol employs low-cost potassium fluoride as the fluorine source. The operational simplicity and mild reaction conditions allow for the rapid synthesis of a wide range of aliphatic fluoride compounds in good yields.

Aryne triggered [2,3]-sigmatropic rearrangement of allyl and propargyl thioethers

An efficient protocol for [2,3]-sigmatropic rearrangement of allyl and propargyl thioethers is reported. The key sulfonium ylide intermediate is in situ formed via S-arylation of arynes. This transition metal-free method allows for ready access to a wide array of functionalized thioether derivatives in good to excellent yields.

Synthesis of 3-aryl-3-benzazepines via aryne [1,2] Stevens rearrangement of 1,2,3,4-tetrahydroisoquinolines

An efficient method for the synthesis of 3-aryl-3-benzazepines via aryne induced [1,2] Stevens rearrangement of 1,2,3,4-tetrahydroisoquinolines is described.

Copper-catalyzed carbene insertion into the sulfur–sulfur bond of benzenesulfonothioate

An unprecedented copper-catalyzed intermolecular sulfur–sulfur bond insertion between aryldiazoacetates and benzenesulfonothioate has been successfully developed.

Diverse ring opening of thietanes and other cyclic sulfides: an electrophilic aryne activation approach

An electrophilic aryne-activated ring opening reaction of saturated sulfur heterocycles is achieved with a wide range of nucleophiles.

Rh(ii)/phosphine-cocatalyzed synthesis of dithioketal derivatives from diazo compounds through simultaneous construction of two different C–S bonds

Rhodium(ii)/phosphine-cocatalyzed bis-sulfuration of α-diazocarbonyl compounds using thiosulfonates as the sulfenylating agent, which provided two sulfur-containing moieties, was developed via simultaneous inter- and intra-molecular C–S bond formation.

Recent advances in molecular rearrangements involving aryne intermediates

A concise account on the recent developments in molecular rearrangements proceeding via the aryne intermediate is presented thereby shedding light on the synthetic potential of this versatile intermediate.

A concise synthesis of (E)-3-aryl-2,3,4,5-tetrahydro-1H-3-benzazonines by aryne induced [2,3] Stevens rearrangement of 1,2,3,4-tetrahydroisoquinolines

(E)-3-Aryl-2,3,4,5-tetrahydro-1H-3-benzazonines were prepared in moderate to good yields with excellent diastereoselectivity via aryne induced [2,3] Stevens rearrangement.

Synthesis of Functionalized β-Keto Arylthioethers by the Aryne Induced [2,3] Stevens Rearrangement of Allylthioethers

A mild and transition-metal-free synthesis of β-keto arylthioethers has been developed by the aryne triggered [2,3] Stevens rearrangement of allylthioethers. The key sulfur ylide intermediate for the rearrangement was formed by the S-arylation of allylthioethers with arynes generated from 2-(trimethylsilyl)aryl triflates using CsF. Later, the reaction products are converted into valuable heterocycles in two steps.