Fujii-Ohno indole synthesis

Several investigators have uncovered additional copper-catalyzed indole syntheses from 2-ethynylanilines accompanied by in situ indole functionahzation. Yamamoto and colleagues reported the synthesis of Af-(alkoxybenzyl) indoles from the copper-catalyzed tandem reaction between 2-alkynyl-Af-arylideneanihnes and alcohols (Cul, toluene, 100°C, 55%-83%) [26], Ohno, Fujii, and coworkers employed a domino three-component copper-catalyzed process to prepare 2-(aminomethyl)indoles [27, 28] and... 

Recently, Fujii and Ohno, incorporated a Mannich-type aminomethylation of alkynes 131 in the presence of para-formaldehyde 132 and secondary amines 133 into a cascade cydization leading to 2-aminomethyl indole derivatives 134 (Scheme 9.50) (211]. The proposed mechanism (Scheme 9.51) is similar to that suggested by Kabalka for the analogous benzo(f>]fiiran synthesis (Scheme 9.5). 

Direct Synthesis of 2-(Aminomethyl)indoles through Copper(I)-Catalyzed Domino Three-Component Couphng and Cyclization Reactions Hiroaki Ohno, Yusuke Ohta, Shinya Oishi and Nobutaka Fujii Angew. Chem., Int. Ed. 2007, 46, 2295—2298. Reproduced with permission... 

Facile Synthesis of 1,2,3,4-Tetrahydro-b-carbolines by One-Pot Domino Three-Component Indole formation and Nucleophihc Cyclization Yusuke Ohta, Shinya Oishi, Nobutaka Fujii and Hiroaki Ohno Org. Lett. 2009, 11, 1979-1982. Reproduced with permission... 

A novel three-component coupling reaction for the synthesis of 2-(aminomethyl) indoles and polycyclic indole derivatives from readily available N-protected ethynylanilines, amines, and aldehydes was reported by Ohno, Fujii, and coworkers. This is the first copper catalytic multicomponent construction of an indole ring that produces water as the only by-product. Two C-N bonds and one C-C bond are formed, whereas C(sp)-H bonds of alkynes and C(sp )-H bonds of aldehydes were activated in this reaction [45-48] (Scheme 8.19). 

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