Direct Synthesis of Sulfonylated Spiro[indole-3,3'-pyrrolidines] by Silver-Mediated Sulfonylation of Acrylamides Coupled with Indole Dearomatization

Photoredox-Catalyzed Synthesis of 3-Sulfonylated Pyrrolin-2-ones via a Regioselective Tandem Sulfonylation Cyclization of 1,5-Dienes

A mild, visible-light-induced, regioselective cascade sulfonylation-cyclization of 1,5-dienes with sulfonyl chlorides through the intermolecular radical addition/cyclization of alkenes C(sp²)-H was developed. This procedure proceeds well and affords a mild and efficient route to a range of monosulfonylated pyrrolin-2-ones at room temperatures.

Photoinduced Photocatalyst-Free Cascade Cyclization of Alkynes with Sodium Sulfinates for the Synthesis of Benzothiophenes and Thioflavones

The subject of this investigation is a new method for the construction of sulfonylated heterocycles which overcomes the limitations of classical approaches using a cheap feedstock sulfonylating agent, especially under photocatalyst- and metal-free conditions.

NBS-induced intramolecular annulation reactions for the divergent synthesis of fused- and spirocyclic indolines

An NBS-induced intramolecular annulation of 3-(1H-indol-3-yl)-N-alkoxypropanamide is described. The reactions proceed well and quickly under mild conditions with the help of a base. It was found that C2-substituents on the indole ring in 3-(1H-indol-3-yl)-N-alkoxypropanamide have a great influence upon the reaction. By using C2-methyl- and C2-phenyl-3-(1H-indol-3-yl)-N-alkoxypropanamide as templates, practical protocols for the divergent synthesis of fused- and spirocyclic indoline compounds were studied and established.

Metal- and base-free tandem sulfonylation/cyclization of 1,5-dienes with aryldiazonium salts via the insertion of sulfur dioxide

A metal- and base-free 5-endo-trig sulfonylative cyclization between 1,5-dienes, aryldiazonium salts and SO₂ (from SOgen) is presented. This method could successfully produce sulfonylated pyrrolin-2-ones in one pot with excellent regioselectivity and good-to-excellent yields. This strategy features mild reaction conditions and broad substrate scope. Moreover, a scale-up reaction and three synthetic applications demonstrate the practicality of this method. Lastly, control experiments indicate that the 5-endo-trig sulfonylative cyclization may proceed in a radical pathway.

A new metal- and base-free method for synthesizing sulfonylated pyrrolin-2-ones from 1,5-dienes, aryldiazonium salts and SO₂ is presented. This transformation features mild reaction conditions and broad substrate scope.

Friedel-Crafts Benzylation of Unprotected Anilines with Indole-3- carbinols to Access Trifluoro-methyl(indolyl)phenylmethanes

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An unprecedented protocol for the efficient and highly chemoselective alkylation of unprotected anilines with deactivated CF3-indole-3-carbinols promoted by In(OTf)3 has been developed. A series of diversified trifluoromethylated (indolyl)phenylmethanes were produced featuring the C-alkylation in moderate to high chemical yields and with high regioselectivities.

Alkylation/Ipso-cyclization of Active Alkynes Leading to 3-Alkylated Aza- and Oxa-spiro[4,5]-trienones

A method for the preparation of 3-alkylated spiro[4.5]trienones via alkylation/ipso-cyclization of activated alkynes with 4-alkyl-DHPs under transition-metal-free conditions is proposed. This alkylation successively undergoes the generation of alkyl radicals, addition of alkyl radicals to the alkynes, and intramolecular ipso-cyclization. The mechanism studies suggest that the alkylation/ipso-cyclization involves a radical process. This ipso-cyclization procedure shows a series of advantages, such as accessibility, mild conditions, high efficiency, greater safety, and an environmentally friendly method.

Preparation of selenyl 1,3-oxazines via PhICl2/Cu2O-promoted aminoselenation of O-homoallyl benzimidates with diselenides

A practical electrophilic aminoselenation of O-homoallyl benzimidate with diselenides promoted by PhICl₂/Cu₂O has been developed. The easily available and stable diselenides were used as selenium sources. Various selenyl 1,3-oxazines, which are important frameworks in medicinal and biological chemistry, were easily obtained in moderate to good yields for the first time. Easy scaleup and scalability make this method attractive for the preparation of other valuable organoselenides.

Metal-Free Sulfonylative Spirocyclization of Indolyl-ynones via Insertion of Sulfur Dioxide: Access to Sulfonated Spiro[cyclopentenone-1,3'-indoles]

A three-component sulfonylative spirocyclization of indolyl ynones with aryldiazonium salts and a sulfur dioxide surrogate of DABCO·(SO₂)₂ has been developed, providing a range of sulfonated spiro[cyclopentenone-1,3'-indoles] in moderate to good yields. This transformation was initiated by an in situ generated arylsulfonyl radical and proceeded efficiently under metal-free conditions, involving a radical-induced dearomative cascade cyclization accompanied by the insertion of sulfur dioxide. This protocol provides an efficient and convenient method to access sulfonated spiroindolenines, and tolerant various functional groups.

Copper-Catalyzed Aminosulfonylation of O-Homoallyl Benzimidates with Sodium Sulfinates to Access Sulfonylated 1,3-Oxazines

A facile copper-catalyzed aminosulfonylation of O-homoallyl benzimidates with sodium sulfinates in the presence of tert-butyl peroxybenzoate (TBPB) and XPhos ligand has been developed. By using this protocol, a variety of potentially bioactive 1,3-oxazines were directly synthesized. This method has the merits of a cheap catalyst, easily available and stable sulfone reagents, and simple operation.

Palladium-Catalyzed Synthesis of 1-Vinyltetrahydro-β-carbolines and Aza-spiroindolenines: Access to the Syntheses of 1-Vinyl-β-carbolines and Eudistomins Y1 and Y2

A general synthesis of 1-vinyltetrahydro-β-carbolines (THBCs) has been achieved via palladium(0)-catalyzed cyclocondensation between allenyltryptamines and aryl iodides. Aza-spiroindolenines could also be accessed from the N-unsubstituted indole substrates by simply tweaking the reaction conditions. DDQ-mediated oxidation of THBCs easily afforded β-carbolines, which could be synthetically transformed into 1-aroyl-β-carbolines of pharmacological interest. Formal total syntheses of eudistomins Y1 and Y2 have also been achieved.

Synthesis and applications of sodium sulfinates (RSO2Na): a powerful building block for the synthesis of organosulfur compounds

This review highlights the preparation of sodium sulfinates (RSO2Na) and their multifaceted synthetic applications. Substantial progress has been made over the last decade in the utilization of sodium sulfinates emerging as sulfonylating, sulfenylating or sulfinylating reagents, depending on reaction conditions. Sodium sulfinates act as versatile building blocks for preparing many valuable organosulfur compounds through S-S, N-S, and C-S bond-forming reactions. Remarkable advancement has been made in synthesizing thiosulfonates, sulfonamides, sulfides, and sulfones, including vinyl sulfones, allyl sulfones, and β-keto sulfones. The significant achievement of developing sulfonyl radical-triggered ring-closing sulfonylation and multicomponent reactions is also thoroughly discussed. Of note, the most promising site-selective C-H sulfonylation, photoredox catalytic transformations and electrochemical synthesis of sodium sulfinates are also demonstrated. Holistically, this review provides a unique and comprehensive overview of sodium sulfinates, which summarizes 355 core references up to March 2020. The chemistry of sodium sulfinate salts is divided into several sections based on the classes of sulfur-containing compounds with some critical mechanistic insights that are also disclosed.

Strategies and methodologies for the construction of spiro-γ-lactams: an update

This review gives an insight into the most recent synthetic methodologies towards spiro-γ-lactams, a class of compounds that are present in a wide range of synthetic bioactive and naturally occurring molecules.