Rh(III)-Catalyzed [3 + 2] Annulation of Aniline Derivatives with Vinylsilanes via C–H Activation/Alkene Cyclization: Access to Highly Regioselective Indoline Derivatives

Abstract

The Rh­(III)-catalyzed reaction of aniline derivatives that contain a pyrimidine directing group with vinylsilanes results in the formation of C3-substituted indoline derivatives in a highly regioselective manner via a C–H activation/alkene cyclization cascade. The results of the mechanistic experiments indicate that C–H bond cleavage is not the rate-determining step and that the reaction proceeds via the formation of a six-membered rhodacycle as a key catalytic species through a pyrimidine-directed electrophilic ortho-C–H rhodation.

Highly Regioselective Synthesis of 2‐Acylindolines through Cobalt‐Catalyzed C−H Activation/[3+2] Annulation of Aniline Derivatives and Acrylates

“…Based on the above studies and previous literature, [11] we proposed the mechanism of this C−H activation/[3+2] annulation (Scheme 4). Catalytic intermediate I was generated by activation of Cp*Co(CO)I 2 by AgSbF 6 .…”

“…Based on the above studies and previous literature, [11] [a] Reactions conducted on a 0.1 mmol scale based on 1, 2 eq of 2, using 10 mol % Cp*Co(CO)I 2 as catalyst, 20 mol % AgSbF 6 as additive, 2 eq Ag 2 CO 3 as oxidant, and reacted for 24 h under 130 °C. [b] Isolated yield after chromatographic purification.…”

“…Comparatively, intermolecular C−H activation processes have been less reported to synthesize 2‐substituted indolines, mainly because catalytic intermediates prefer β‐elimination to construct alkenyl products (Scheme 1c). Only a few groups, such as Jiang, [9] Jana, [10] Chatani, [11] Booker‐Milburn, [12] Yang [13] and Zhong [14] used precious metal catalysts Pd, Ru or Rh to achieve indolines synthesis via intermolecular C−H activation (Scheme 1c). Furthermore, these methods used limitative conditions (such as electrochemistry) and the products were generally 2‐aryl or alkyl indolines.…”

“…To begin our studies, we chose N ‐phenylpyrimidin‐2‐amine 1 a , which was readily available from aniline, [11] and benzyl acrylate 2 a as model substrates. At the outset, we explored the reaction optimization using three Co catalysts Cp*Co(CO)I 2 , [Cp*Co(CH 3 CN) 3 ](SbF 6 ) 2 and [Cp*CoI 2 ] 2 , AgSbF 6 as an additive, Ag 2 CO 3 as an oxidant in DCE at 120 °C for 24 h. The 2‐acylindoline product 3 aa was generated in 71%, 51% and 70% yields (Table 1, entries 1–3), respectively.…”

Rhodium(III)-Catalyzed Oxidative C–H Alkylation of Aniline Derivatives with Allylic Alcohols To Produce β-Aryl Ketones

“…While the use of a pyrimidine-directing group in the C–H bond alkylation of aniline derivatives has been widely explored, sensitive alkylating reagents such α-oxocarboxylic acids or aldehydes, diazo compounds, cyclopropanols, diazoesters, and others were used. Our group recently reported the versatile C–H functionalization of aniline derivatives such as amidation, branch-alkenylation, and regioselective indoline synthesis using a pyrimidine-directing group . In a continuation of this aniline C–H functionalization, we report herein the Rh­(III)-catalyzed oxidative C–H alkylation of aniline derivatives with allyl alcohols through pyrimidine chelation assistance (Scheme b).…”