Co(II)-Catalyzed C–H/N–H Annulation of Cyclic Alkenes with Indole-2-carboxamides at Room Temperature: One-Step Access to β-Carboline-1-one Derivatives

Abstract

We report herein a cobalt-catalyzed 8-aminoquinoline-directed highly regio-and stereoselective C−H/N−H activation annulation of indole-2-carboxamides with 1,2-dihydronaphthalene for the synthesis of β-carboline-1-one derivatives at room temperature. A cheaper and commercially available cobalt catalyst has been used for this transformation. The protocol tolerates a wide range of functionalities, affording β-carboline-1-one derivatives in good yields. An initial mechanistic study revealed a reversible cyclometalation to be operative.

Co(II)‐Catalysed C−H/N−H Annulation of Cyclic Alkenes with Benzamides at Room Temperature: An Easy Access to the Core Skeleton of Hexahydrobenzo[c]phenanthridine‐type Alkaloids

“…Based on our mechanistic findings and literature reports [11,16] a possible catalytic cycle is proposed (Scheme 5). Initially Mn(III) oxidizes Co(II) to Co(III).…”

“…The obtained KIE value of 1.6 in the parallel experiment indicates that the CÀ H activation might be the turnover-limiting step. [15] Based on our mechanistic findings and literature reports [11,16]…”

“…As an extension of the communicated methodology [11] towards β ‐carboline‐1‐one derivatives; we investigated the versatility of substituted benzamides 1 bearing a wide array of functional groups with dihydronaphthalene ( 2 a ) as coupling partner (Scheme 2).…”

Annulation of Indole-2-Carboxamides with Bicycloalkenes Catalyzed by Ru(II) at Room Temperature: An Easy Access to β-Carboline-1-one Derivatives under Mild Conditions

“…■ EXPERIMENTAL SECTION 16 All reactions were performed in sealed tubes. Chemicals were purchased from Alfa-aesar, Sigma-Aldrich, and Spectrochem and were used without any purification.…”