Redox-Neutral Strategy for Sulfilimines Synthesis via S-Arylation of Sulfenamides

1,2-Difunctionalization of Aryne with Sulfenamide and Organohalide: Mild and Metal-Free Access to S-(o-Halo)aryl Sulfilimine

A mild and metal-free approach has been developed for 1,2-difunctionalization of aryne using sulfenamides as a nucleophile and a halogen source (CX4) as an electrophile to synthesize S-(o-halo)aryl sulfilimines. The late-stage functionalizations of halide handles via Suzuki-Miyaura and Buchwald-Hartwig reactions exhibit the synthetic utilities of the products. The chemoselectivity, regioselectivity, rapidity, and use of economical CCl4 are the advantages of this protocol.

Copper-Catalyzed Sulfur Alkylation of Sulfenamides with N-Sulfonylhydrazones

Sulfilimines are valuable compounds in both organic synthesis and pharmaceuticals. In this study, we present a copper-catalyzed sulfur alkylation of sulfenamides with N-sulfonylhydrazones. In contrast to prior findings, hydrazones derived from aldehydes act as donor-type carbene precursors, effectively engaging in coupling with sulfenamides via a copper catalyst, demonstrating exclusive S selectivity. The utility of the protocol was highlighted in the rapid access to a wide range of sulfoximine derivatives.

Decarboxylative Radical Sulfilimination via Photoredox, Copper, and Brønsted Base Catalysis

Sulfilimines, the aza-variants of sulfoxides, are key structural motifs in natural products, pharmaceuticals, and agrochemicals; and sulfilimine synthesis is therefore important in organic chemistry. However, methods for radical sulfilimination remain elusive, and as a result, the structural diversity of currently available sulfilimines is limited. Herein, we report the first protocol for decarboxylative radical sulfilimination reactions between sulfenamides and N-hydroxyphthalimide esters of primary, secondary, and tertiary alkyl carboxylic acids, which were achieved via a combination of photoredox, copper, and Brønsted base catalysis. This novel protocol provided a wide variety of sulfilimines, in addition to serving as an efficient route for the synthesis of S-alkyl/S-aryl homocysteine sulfilimines and S-(4-methylphenyl) homocysteine sulfoximine. Moreover, it could be used for late-stage introduction of a sulfilimine group into structurally complex molecules, thereby avoiding the need to preserve labile organosulfur moieties through multistep synthetic sequences. A mechanism involving photocatalytic substrate transformation and copper-mediated C(sp3 )-S bond formation is proposed.

Synthesis of N-Acylsulfenamides from (Hetero)Aryl Iodides and Boronic Acids by One-Pot Sulfur-Arylation and Dealkylation

A general one-pot approach to diverse N-acylsulfenamides from a common S-phenethylsulfenamide starting material is reported. This approach was demonstrated by C-S bond formation utilizing commercially abundant (hetero)aryl iodides and boronic acids to provide sulfilimine intermediates that undergo thermal elimination of styrene. In contrast, all prior approaches to N-acylsulfenamides rely on thiol inputs to introduce sulfenamide S-substituents. A broad scope of reaction inputs was demonstrated including for approved drugs and drug precursors with dense display of functionality. Several different types of sulfur functionalization were performed on a sulfenamide derived from a complex precursor of the blockbuster anticoagulant drug apixaban, highlighting the utility of this approach for the introduction of high oxidation state sulfur groups in complex bioactive compounds. Mechanistic studies established that the key styrene elimination step proceeds by a concerted elimination that does not require reagents or catalysts, and therefore, this one-pot approach should be applicable to the synthesis of N-acylsulfenamides utilizing diverse electrophiles and reaction conditions for C-S bond formation.

Copper-Catalyzed Aerobic S-Amination of Sulfenamides for the Synthesis of Sulfinamidines

Herein, we present a copper-catalyzed oxidative amination of sulfenamides for the synthesis of sulfinamidines. By the employment of air as the terminal oxidant, a diverse array of secondary and primary amines can be efficiently transformed into their corresponding products. This method is well-suited for last-stage functionalization, and the underlying mechanism has been investigated. The transformation is characterized by exceptional chemoselectivity, mild conditions, facile operation, and broad substrate compatibility, which have significant implications for the fields of pharmaceuticals and organic synthesis.

Anomeric Answer to Sulfenamide Stability and α-Nucleophilicity

The S-N bond remains a synthetically challenging motif for organic chemists to access. The problem arises from instability in many sulfenamide derivatives, which has led to fewer S-N bond surrogate molecules compared to their hydroxylamine (NH2OH) and hydrazine (NH2NH2) analogues. In turn, sulfenamides have often been omitted in studies regarding α-nucleophilicity. Herein, we provide factors responsible for the stability of the sulfenamide motif and provide new insights on the nucleophilic properties of sulfenamides as they relate to the α-effect.

Selective S-Arylation of Sulfenamides with Arynes: Access to Sulfilimines

Sulfilimines, the aza analogues of sulfoxides, are of increasing interest in medicinal and agrochemical research programs. However, the development of efficient routes for their synthesis has remained relatively unexplored. In this study, we report a transition metal-free, selective S-arylation reaction between sulfenamides and arynes, enabling the facile preparation of structurally diverse sulfilimines under mild and redox-neutral conditions in good yields. The application value of our method was further demonstrated by scale-up synthesis, downstream derivatization, and robustness screen.

Synthesis of Sulfilimines via Multicomponent Reaction of Arynes, Sulfamides, and Thiosulfonates

In this work, a facile and efficient method for the synthesis of sulfilimines through multicomponent reaction of arynes, sulfamides, and thiosulfonates was developed. A variety of structurally diverse substrates and functional groups were very compatible in the reaction, giving the corresponding sulfilimines in good to high yields. This protocol could be conducted on a gram scale, and the product was easily converted to sulfide and sulfoximine. Mechanism studies revealed that sulfenamide generated in situ is the key intermediate for the reaction.

Hypervalent Iodine Mediated Synthesis of Sulfinamidines from Sulfenamides

In this study, we present a novel, efficient method for the oxidative amination of sulfenamides using diacetoxyiodobenzene (PhI(OAc)2) and amines under basic conditions. This innovative technique streamlines the synthesis of sulfinamidines under mild, metal-free conditions, achieving outstanding yields of up to 99%. Furthermore, we propose possible pathways that elucidate the observed molecular sequence of events in this reaction. This cutting-edge approach not only advances the synthesis of valuable sulfinamidine compounds but also expands the synthetic toolbox available to chemists, paving the way for future discoveries in organic synthesis and potential applications in medicinal chemistry.

Synthesis of Sulfilimines via Aryne and Cyclohexyne Intermediates

An efficient and metal-free approach for the synthesis of sulfilimines from sulfenamides with aryne and cyclohexyne precursors has been developed. The reaction proceeds through unusual S-C bond formation, which offers a novel and practical entry to access a wide range of sulfilimines in moderate to good yields with excellent chemoselectivity. Moreover, this protocol is amenable to gram-scale synthesis and is applicable to the transformation of the products into useful sulfoximines.

Sulfur-Arylation of Sulfenamides via Ullmann-Type Coupling with (Hetero)aryl Iodides

Sulfur-(hetero)arylation of sulfenamides with commercially abundant (hetero)aryl iodides by Ullmann-type coupling with inexpensive copper(I) iodide as the catalyst is reported. A broad scope of reaction inputs was demonstrated, including both aryl and alkyl sulfenamides and highly sterically hindered aryl and 5- and 6-membered ring heteroaryl iodides. Relevant to many bioactive high oxidation state sulfur compounds, the (hetero)arylation of S-methyl sulfenamides is reported, including for complex aryl iodides. Smiles rearrangement of electron-deficient S-heteroaryl sulfilimines is also disclosed.

Metal-Free Chemoselective S-Arylation of Sulfenamides To Access Sulfilimines

A novel and efficient S-arylation of sulfenamides with diaryliodonium salts for the synthesis of sulfilimines is developed. The reaction proceeds smoothly under transition-metal-free and air conditions, giving rapid access to sulfilimines in good to excellent yields via selective S-C bond formation. This protocol is scalable and exhibits a broad substrate scope, good functional group tolerance, and excellent chemoselectivity.

Base-Promoted S-Arylation of Sulfenamides for the Synthesis of Sulfilimines

Sulfilimines are key intermediates to common motifs in medicines and agrochemicals. Typically, this class of compounds are prepared by imidation of thioethers, transition-metal-catalyzed or base-promoted sulfur alkylation and transition-metal-catalyzed sulfur arylation. Here, we report a practical and efficient base-mediated sulfur arylation reaction for the preparation of sulfilimines. A wide range of N-acyl and N-aryl sulfenamides react with various diaryliodonium salts smoothly to afford the sulfilimines in high yields with excellent chemoselectivities.