Benzocarbazole Synthesis via Visible-Light-Accelerated Rh(III)-Catalyzed C–H Annulation of Aromatic Amines with Bicyclic Alkenes

Abstract

A visible-light-accelerated Rh­(III)-catalyzed C–H annulation of aromatic amines with bicyclic alkenes for the synthesis of benzocarbazole derivatives was developed. In this approach, with the cooperation of rhodium catalysis and visible-light irradiation, various aromatic amines reacted with oxabicyclic alkenes and azabicyclic alkenes smoothly at room temperature, delivering the corresponding bridged oxa or aza tetrahydro benzocarbazoles in good to excellent yields. Moreover, a series of benzo­[b]­carbazoles were synthesized conveniently through further aromatization in one pot. The potential of this method was demonstrated via directing-group removal, derivatization, a scale-up reaction, and fluorescence investigations.

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

“…Silica gel (200-300 mesh, Qingdao) was used for flash chromatography. 1 H NMR, 13 C NMR, and 19 F NMR spectra were obtained using a Bruker DRX 400/600 spectrometer at 400/600 MHz, 100/150 MHz, and 376/471 MHz respectively. Chemical shifts are reported in units of parts per million (ppm) downfield from tetramethylsilane (TMS), and all coupling constants are reported in hertz.…”

“…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.…”

LNL-Carbazole Pincer Ligand: More than the Sum of Its Parts

“…232 The most prominent structural feature in the crystal structures of the rhodium complex 194 and iridium complexes 208 and 210 is the strong distortion of the CO ligand out of the square planar geometry around the metal center. 140,232 The possibility of increased lability of the ligand due to carbonyl distortion was ruled out in 13 CO exchange experiments performed on rhodium complex 194 (Scheme 30). No exchange was observed despite overpressure of 13 CO gas, irradiation, or prolonged heating, in accordance with the strong π-back-donation inferred from IR spectroscopy.…”

“…140 The X-ray crystal structure of octahedral 205 exhibits the iodine and methyl group at the axial positions trans to each other, typical of oxidative addition by the S N 2 mechanism. The carbonyl group was shown to be more labile in 205 than in 194 based on 13 CO exchange experiments, where carbonyl exchange was observed at room temperature within a short time (Scheme 30).…”

Lewis Acid-Catalyzed 2,3-Dihydrofuran Acetal Ring-Opening Benzannulations toward Functionalized 1-Hydroxycarbazoles

“…The synthesis of carbazoles generally follows two distinct approaches ( Figure 2 ): (a) an annulation reaction to generate the central pyrrole ring or (b) a benzannulation reaction in which a benzene ring is appended on the five-member ring of an indole [ 15 , 16 , 17 , 18 , 19 ]. While several syntheses have been reported [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ], the abundant presence of the carbazole core in bioactive molecules and photoelectronic materials makes them attractive targets for the development of new synthetic methodologies, often targeting new substitution patterns, modularity and mild reaction conditions.…”