One‐Pot Regio‐ and Diastereoselective Synthesis of Tetrahydro‐α‐carbolines via Cascade Reactions of Iminoindolines with Morita‐Baylis‐Hillman Bromides of Nitroalkenes

• Published in: European journal of organic chemistry Vol. 2022; no. 3
• Main Authors: Sivanandan, Sudheesh T., Chauhan, Diksha, Namboothiri, Irishi N. N.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 21.01.2022
• Subjects: Annulation; Bromides; Cascade chemical reactions; Diastereoselectivity; Iminoindoline; Morita-Baylis-Hillman; Reaction time; Stereoselectivity; Substrates; Tetrahydro-α-carboline
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.202101426

A mild and metal‐free method for the one‐pot synthesis of highly substituted tetrahydro‐α‐carbolines from Morita‐Baylis‐Hillman (MBH) bromides of nitroalkenes and iminoindolines has been demonstrated. Cascade reaction of MBH bromides with tosyliminoindolines occurs with regio‐ as well as diastereoselectivity in a formal [3+3] manner to form various tetrahydro‐α‐carbolines with wide substrate scope under mild conditions. All the products were obtained in high yields within a short reaction time. Also, the synthetic efficiency of the methodology was demonstrated by a gram scale experiment and by further converting them into 3‐nitro‐α‐carbolines. Tetrahydro‐α‐carbolines and α‐carbolines bearing a key nitro group have been synthesized via [3+3] annulation of tosyliminoindolines with nitroallylic bromides.