Iridium-Catalyzed Hydrogen Transfer: Synthesis of Substituted Benzofurans, Benzothiophenes, and Indoles from Benzyl Alcohols

Abstract

An iridium-catalyzed hydrogen transfer has been developed in the presence of p-benzoquinone, allowing the synthesis of a diversity of substituted benzofurans, benzothiophenes, and indoles from substituted benzylic alcohols.

Synthesis, Structures of Benzoxazolyl Iridium(III) Complexes, and Applications on C–C and C–N Bond Formation Reactions under Solvent-Free Conditions: Catalytic Activity Enhanced by Noncoordinating Anion without Silver Effect

“…The borrowing hydrogen methodology involves (1) oxidation of alcohols or ammonia to the corresponding carbonyl compounds or imines; (2) alkylation of ketones, alcohols, or amines to form unsaturated carbonyl compounds or imines; and (3) reduction of the C–C or C–N bonds using the borrow hydrogen atoms from alcohols or amines (Scheme ). , Generally, among these transformations, the catalyst plays a crucial role in every step. To date, although some metals (Pd, Au, Ag, Cu, Fe, Ni, Os, and Rh,) have been studied, Ru and Ir − are still shown to be the most effective and promising catalysts for C-alkylation and N-alkylation.…”

Iridium-Catalyzed Direct Synthesis of Tryptamine Derivatives from Indoles: Exploiting N-Protected β-Amino Alcohols as Alkylating Agents

“…A variety of transition-metal catalysts well-known to be highly active in hydrogen autotransfer reactions, including Pd/C, RuCl 2 (PPh 3 ) 3 , [Ir­(cod)­Cl] 2 , [Ir­(coe) 2 Cl] 2 , [Ir­(OMe)­(cod)] 2 , and RuHCl­(CO)­(PPh 3 ) 3 , were screened. We found that the iridium dimer [Cp*IrCl 2 ] 2 was the most efficient catalyst. After 48 h, we observed complete consumption of the indole and selective formation of the desired N -acetyltryptamine (35% yield; Table , entry 9), without traces of the N 1 -alkylated product.…”

Hetero-Type Benzannulation Leading to Substituted Benzothio-Phenes

“…Therefore, a number of syntheses have been developed to date [1,2]. Representative methods for the construction of simple, unsubstituted benzothiophenes are categorized into several approaches (Scheme 1): (i) Hinsberg-type annulations [7][8][9], (ii) Friedel-Crafts type annulations [10][11][12][13], (iii) Wittig-type condensations of phosphonium salts [14,15], (iv) Metal-catalyzed thiolation annulations [16][17][18], (v) Pd-catalyzed C-H arylations [19], and others [20][21][22][23][24].…”