An efficient approach to 1,2,3-trisubstituted indole via rhodium catalyzed carbene C_sp3–H bond insertion

Abstract

A method for convenient synthesis of N-alkyl-2-aryl-indole-3-carbaldehyde has been described. A variety of highly valuable indolyl aldehydes have been prepared through this method. Electron donating groups on both aromatic rings (anilinyl and benzyl) facilitate the formation of the desired products. A benzylic C-H insertion by rhodium carbene is the key step for this transformation.

Stereoselective Construction of Bridged trans-aza-Bicyclo[7/6,3/2,1]alkenyl Imines through Ring Expansion aza-Cope Rearrangement

“…However, when aromatic amino enyne 3g reacted with TsN 3 , triazole 5g was the only product isolated in 84% yield (entry 9), indicating that the cyclic indoline group itself failed to act as an effective internal base to promote the formation of sulfonyl ketenimine in the reaction with sulfonyl azide. To our delight, incorporation of excess DIPEA (5 equiv) as an external base into the reaction system (method b) restored the ketenimine formation/cyclization/aza-Cope rearrangement pathway to deliver benzo-fused bicycle 4g (entry 10).…”

Catalytic Insertion Reactions of α‐Imino Carbenoids

“…Around the same time, Xu and co-workers developed a convenient method to prepare indole-3-carbaldehydes 30 from 2-(N-alkyl-N-benzyl)-anilinyl triazoles (Scheme 7b). [20] The reaction proceeded via rhodium catalyzed CÀ H insertion of benzyl aromatic amine followed by dehydrogenative aromatization and then hydrolysis of imine by using excess K 2 CO 3 in MeOH. In this reaction, electronically rich triazoles performed better by providing higher yields in comparison to triazoles having an electron withdrawing group.…”

Recent Advances in the Synthesis of 5‐MemberedN‐Heterocycles via Rhodium Catalysed Cascade Reactions

“…In past few years, C−H functionalization has shown extensive growth in enabling new methodologies for organic synthesis [15a–g] . Donor/acceptor metallocarbenes accessed via metal‐catalyzed decomposition of aryl diazoacetates are found to be adequately reactive to functionalize C−H bonds [15h–n] . Presently, Chuprakov and co‐workers unveiled a latent diazo compounds possessing an α ‐imino acceptor group by retro‐6π electrocyclization of 4‐aryl‐ N ‐sulfonyl‐1,2,3‐triazoles, as a competent alternative to aryl diazoacetates, owing to their ability to access a wide variety of traditional Rh(II)‐catalyzed transformations [15o] .…”