Kunbing Ouyang,†,‡ Wei Hao,† Wen-Xiong Zhang,*,†,§ and Zhenfeng Xi† †Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China ‡Institute of Chemistry, Chinese Academy of Sciences (CAS), Beijing 100190, China State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China

Transition-Metal-Catalyzed Cleavage of C-N Single Bonds.

Metal-stabilized carbenes derived from diazo compounds have become broadly useful reactive intermediates for organic synthesis. This tutorial review will describe the recent advances in using N-sulfonyl-1,2,3-triazoles as precursors for the formation of metal-bound imino carbene intermediates. These intermediates undergo a variety of synthetically useful transformations, which include transannulation reactions to generate new heterocycles, cyclopropanation and subsequent ring expansions, ylide formation with subsequent rearrangements, and C–H functionalization. Furthermore, many of these transformations can be conducted with high levels of enantioselectivity by use of chiral rhodium(II) catalysts.

Reactions of metallocarbenes derived from N-sulfonyl-1,2,3-triazoles

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.

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

Metal carbenes usually possess versatile reactivities that are controlled by the presence of both the metals and the ligands. Diazo compounds are commonly used for the generation of such species through elimination of nitrogen. However, they are often unstable, explosive, and toxic, which limits their applications in large-scale syntheses. Thus, identifying sustainable and safe surrogates for the generation of metal carbenes has attracted great attention. In this Review, we summarize some of the most important breakthroughs in the generation, catalytic reactions, and selectivity control of metal carbenes from non-diazo starting compounds.

New Approaches to the Synthesis of Metal Carbenes

The rhodium-catalyzed dearomatizing [3 + 2] annulation reaction of 4-(3-arylpropyl)-1,2,3-triazoles is described. It provides a straightforward synthetic pathway from simple 5-aryl-1-alkynes leading to tricyclic 3,4-fused dihydroindoles via the corresponding 1,2,3-triazoles.

Intramolecular Dearomatizing [3 + 2] Annulation of α-Imino Carbenoids with Aryl Rings Furnishing 3,4-Fused Indole Skeletons

This method yields α-substituted α-amino ketone derivatives which are substructures of bioactive compounds and intermediates in the synthesis of α-amino alcohols.

One‐Pot Procedure for the Introduction of Three Different Bonds onto Terminal Alkynes through N‐Sulfonyl‐1,2,3‐Triazole Intermediates

A stereoselective method for synthesis of trans-2,3-disubstituted 2,3-dihydropyrroles is reported. N-Sulfonyl-1,2,3-triazoles prepared from terminal alkynes generate α-imino rhodium carbene complexes, which when combined with α,β-unsaturated aldehydes produce trans-2,3-disubstituted dihydropyrroles. The method can be successfully applied to a one-pot process starting from terminal alkynes.

Stereoselective Synthesis of 2,3-Dihydropyrroles from Terminal Alkynes, Azides, and α,β-Unsaturated Aldehydes via N-Sulfonyl-1,2,3-triazoles

1-Sulfonyl-1,2,3-triazoles undergo a Doyle–Kirmse reaction upon treatment with allylic sulfides in the presence of a rhodium(II) catalyst to afford α-allyl-α-sulfanylimines. Terminal alkynes are re...

Doyle–Kirmse Reaction Using Triazoles Leading to One-pot Multifunctionalization of Terminal Alkynes

Direct production of enaminones from terminal alkynes via rhodium-catalyzed reaction of formamides with N-sulfonyl-1,2,3-triazoles.

Relay actions of copper, rhodium, and gold formulate a one-pot multistep pathway, which directly gives 2,5-dihydropyrroles starting from terminal alkynes, sulfonyl azides, and propargylic alcohols. Initially, copper-catalyzed 1,3-dipolar cycloaddition of terminal alkynes with sulfonyl azides affords 1-sulfonyl-1,2,3-triazoles, which then react with propargylic alcohols under the catalysis of rhodium. The resulting alkenyl propargyl ethers subsequently undergo the thermal Claisen rearrangement to give α-allenyl-α-amino ketones. Finally, a gold catalyst prompts 5-endo cyclization to produce 2,5-dihydropyrroles.

Takamasa Tanaka

Papers

One‐Pot Procedure for the Introduction of Three Different Bonds onto Terminal Alkynes through N‐Sulfonyl‐1,2,3‐Triazole Intermediates

Stereoselective Synthesis of 2,3-Dihydropyrroles from Terminal Alkynes, Azides, and α,β-Unsaturated Aldehydes via N-Sulfonyl-1,2,3-triazoles

Doyle–Kirmse Reaction Using Triazoles Leading to One-pot Multifunctionalization of Terminal Alkynes

Direct production of enaminones from terminal alkynes via rhodium-catalyzed reaction of formamides with N-sulfonyl-1,2,3-triazoles.

One‐Pot Synthesis of 2,5‐Dihydropyrroles from Terminal Alkynes, Azides, and Propargylic Alcohols by Relay Actions of Copper, Rhodium, and Gold