Diarylation of N- and O-nucleophiles through a metal-free cascade reaction

Transition Metal-Free Difunctionalization of Sulfur Nucleophiles

“…The diarylation of N-and O-nucleophiles was proposed to proceed via initial SNAr to form a Meisenheimer complex followed by intramolecular aryl transfer. [15] A related mechanism can be proposed for the S-diarylation, where the S-nucleophile forms the SNAr product A, followed by hydrolysis of the xanthogenate to B and carbonothioate derivative C, followed by intramolecular aryl transfer to yield diarylated product 3 (Scheme 4A). Alternatively, the aryl transfer could proceed before hydrolysis via intermediate D. The SNAr step could proceed via a stepwise or concerted mechanism, as previously reported in S-arylation.…”

“…Based on previous work from our group and literature precedence, [15][16] we commenced our initial investigation using iodonium salt 1a, molecular sulfur (2a), and K2CO3 as a base in DMSO at 80 °C. The desired product 3a was not detected, but 11% of the diaryl ether 3a' was observed instead (Table 1, entry 1).…”

“…[12c] Recently, the Olofsson group developed a sustainable and transition-metal free approach for diarylation of N-and O-nucleophiles using diaryliodonium salts under basic conditions, where both aryl groups and the iodide were retained in the product. [15] The reaction was suggested to proceed through nucleophilic aromatic substitution (SNAr) followed by intramolecular aryl transfer to afford the diarylated product.…”

Organocatalytic Synthesis of Phenols from Diaryliodonium Salts with Water under Metal-Free Conditions

“…Through the efforts for improvement, the photoredox Ni-catalyzed hydroxylation for aryl bromides and chlorides under mild conditions has been developed with water as a mild, green, and inexpensive nucleophile (Scheme b). , In this context, the metal-free coupling of a useful aryl source with water as a nucleophile is believed to be a desirable and challenging approach for phenol synthesis because of its attractive potential in terms of green chemistry. Among hypervalent halogen compounds, diaryliodonium salts are known as mild, less-toxic, and readily accessible arylating agents, and metal-free coupling reactions have been actively developed by taking advantage of their beneficial features. − In the metal-free synthesis of phenols using diaryliodonium salts, hydroxide surrogates, such as benzaldehyde oxime, hydrogen peroxide, and silanols were effectively utilized, avoiding aryne formation under basic conditions (Scheme c). , In view of the weak nucleophilicity of water, we envisaged an organocatalytic approach for phenol synthesis with water that could incorporate a hydroxy group on an aromatic ring through the hydrolysis of a 2-aryloxypyridinium salt, following the O -arylation of a pyridin-2-one derivative with a diaryliodonium salt (Schemes d and e). Herein, we report the metal-free synthesis of phenols from diaryliodonium salts with water by organocatalysis.…”

ortho-Nitro-substituted diaryliodonium salts enabled regioselective cyclization of arylcarboxylic acids toward 3,4-naphthocoumarins

“…6 c More recently, Olofsson et al described an unprecedented reaction pathway using hypervalent iodine compounds, wherein the diarylation of N- and O-nucleophiles was achieved with ortho -fluoro-substituted diaryliodonium salts with strong electron-withdrawing groups. 11 In relation with our great interest in ortho -functionalized diaryliodonium salts and the dual activation, we synthesized a series of ortho -nitro-diaryliodonium salts and explored their properties and reactivities. Meanwhile, Yamaguchi and Muto recently reported a palladium catalysed activation of C–NO 2 bond for the cross coupling reactions.…”