Rapid assembly of structurally diverse cyanamides and disulfanes via base-mediated aminoalkylation of aryl thiourea

A general method for the preparation of cyanamides and disulfanes from aryl thiourea and halide through a base-mediated strategy is described. Mercaptan and N-aryl cyanamide are the key intermediates in the reaction. The current method is convenient, eco-friendly, and has high yields for the synthesis of substituted cyanamide and functional disulfanes in a one-pot procedure from readily available starting materials.

Copper-Catalyzed, Ligand-Controlled N(sp3)- or N(sp)-Selective Arylation of Cyanamides

Cyanamides possess both nucleophilic and electrophilic centers, and their arylation reactions are known to proceed at N(sp3) and C(sp) sites, leading to N-aryl cyanamides or amidines. N(sp) selectivity has also been reported only in the presence of amines, thus leading to guanidines. Herein, we report a general copper-catalyzed ligand-controlled Chan-Lam-Evans arylation of cyanamides proceeding regioselectively at the N(sp3) or N(sp) atoms and leading to either N-aryl cyanamides or dissymmetric carbodiimides. The nature of the ligand, either a bipyridine or a diamine, controls the product distribution and thus offers a divergent entry to useful building blocks from readily available cyanamides.

Facile preparation of dihydro-1,4-benzothiazine derivatives via oxidative ring-expansion of 2-aminobenzothiazoles with olefins

A concise and efficient approach to prepare dihydro-1,4-benzothiazine derivatives is described via oxidative ring-expansion of 2-aminobenzothiazoles with olefins under metal-free conditions. This protocol is applicable for a wide range of readily accessible 2-aminobenzothiazoles and olefins with moderate-to-good yields. The [4+2] heteroannulation between the intermediacy of oxidative ring-opening of 2-aminobenzothiazoles and olefins is suggested to rationalize the formation of the product.

Direct para-Selective C-H Amination of Iodobenzenes: Highly Efficient Approach for the Synthesis of Diarylamines

Iodine(III)-mediated synthesis of 4-iodo-N-phenylaniline from iodobenzene has been achieved, and the reaction can proceed under mild conditions. A variety of functional groups were well tolerated, providing the corresponding products in moderate to good yields. The remaining iodine group provides an effective platform for converting the products into several valuable asymmetric diphenylamines. Most importantly, this reaction can be easily scaled up to the ten-gram scale, highlighting its synthetic utility. The mechanistic study revealed that the in situ generated aryl hypervalent iodine intermediate is the key factor to realize this para-selective C-H amination reaction.

Copper-Catalyzed Alkenylation of Cyanamides

An efficient procedure for the copper-catalyzed cross-coupling between a broad range of cyanamides and iodoalkenes is reported. Upon reaction with catalytic amounts of copper(I) iodide and 2,2'-bisimidazole in the presence of cesium carbonate in DMF at 80 °C, a fast, regioselective, and stereoretentive cross-coupling occurs. This reaction, which was found to have a broad substrate scope, provides the first general entry to N-alkenylcyanamides, building blocks that hold great synthetic potential.

Aryl Transfer Selectivity in Metal-Free Reactions of Unsymmetrical Diaryliodonium Salts

Aromatic rings are found in a wide variety of products, including pharmaceuticals, agrochemicals, and functional materials. Diaryliodonium salts are new reagents used to transfer aryl groups under both metal-free and metal-catalyzed reactions and thereby synthesize arene-containing compounds. This minireview focuses on recent studies in selective aryl transfer reactions from unsymmetrical diaryliodonium salts under metal-free conditions. Reactions reported from 2007 to 2017, which represents a period of significant growth in diaryliodonium salt chemistry, are presented and organized by the type of reactive intermediate formed in the reaction. Specifically, reactions involving λ³ -iodane, λ³ -iodane radical anions, aryl radicals, and arynes are discussed. Chemoselectivity trends in aryl transfer are compared and contrasted across reaction intermediates and translation to potential auxiliaries are posited.

Selective C–N coupling reaction of diaryliodonium salts and dinucleophiles

Ligand-free copper-catalyzed selective N-arylation of dinucleophiles including chiral α-amino amides with diaryliodonium salts as aryl electrophile equivalents was realized. Diaryliodonium salts prefer to react with dinucleophiles at the site of stronger basic amino groups.

Metal-free Synthesis of Aryl Amines: Beyond Nucleophilic Aromatic Substitution

A mild and metal-free approach to C-N coupling is described that employs diaryliodonium salt electrophiles and secondary aliphatic amine nucleophiles. This reaction results in direct ipso-substitution of the iodonium moiety and unsymmetrical aryl(TMP)iodonium salts are primarily employed. Moreover, arene substituents and substitution patterns that currently pose a challenge to classical metal-free methods are accommodated and the alicyclic amine nucleophiles used here are unprecedented in other contemporary metal-free C-N coupling reactions.