A Combined Experimental and Computational Study on the Cycloisomerization of 2‐Ethynylbiaryls Catalyzed by Dicationic Arene Ruthenium Complexes

Abstract

Ruthenium-catalyzed cycloisomerization of 2-ethynylbiaryls was investigated to identify an optimal ruthenium catalyst system. A combination of [η(6) -(p-cymene)RuCl2 (PR3 )] and two equivalents of AgPF6 effectively converted 2-ethynylbiphenyls into phenanthrenes in chlorobenzene at 120 °C over 20 h. Moreover, 2-ethynylheterobiaryls were found to be favorable substrates for this ruthenium catalysis, thus achieving the cycloisomerization of previously unused heterocyclic substrates. Moreover, several control experiments and DFT calculations of model complexes were performed to propose a plausible reaction mechanism.

One-Step Regioselective Synthesis of Benzofurans from Phenols and α-Haloketones

“…2-Methylnaphtho[1–b]furan ( 6b ) [31]. The title compound was obtained as colorless oil (80%), and the analytical data are consistent with those in the literature.…”

Reactions of [2‐(2‐Naphthyl)phenyl]acetylenes and 2‐(2‐Naphthyl)benzaldehyde O‐Phenyloximes: Synthesis of the Angucycline Tetrangulol and 1,10,12‐Trimethoxy‐8‐methylbenzo[c]phenanthridine

“…Examination of the literature[31a], led us to speculate that the desired product 25 would be formed by initial formation of η 2 complex I (Figure ). This complex could then undergo a “Friedel–Crafts”‐type reaction to give II by means of a 6‐ endo ‐ dig cyclization, which would ultimately lead to 25 .…”

“…Reagents and conditions: (a) 29 , h ν , 400 W mercury lamp, Pyrex, tert ‐butyl alcohol, room temp., 58 % for 30 , 28 % for 31 ; (b) 32 , microwave irradiation, EmimPF 4 , tert ‐butyl alcohol, 30 min, 160 °C, 76 % of 30 , 0 % of 31 , …”

Relay Catalysis of Bismuth Trichloride and Byproduct Hydrogen Bromide Enables the Synthesis of Carbazole and Benzo[α]carbazoles from Indoles and α‐Bromoacetaldehyde Acetals

“…8‐Methoxy‐11 H ‐benzo[α]carbazole (3 c) : 66.7 mg, 90%; white solid, mp: 205–206 °C; 1 H (400 Hz, DMSO‐ d 6 , 25 °C): δ =3.88 (s, 3H), 7.05 (dd, J =2.4, 8.8 Hz, 1H), 7.51–7.64 (m, 4H), 7.73 (d, J =2.0 Hz, 1H), 8.01 (d, J =8.0 Hz, 1H), 8.19 (d, J =8.4 Hz, 1H), 8.48 (d, J =8.0 Hz, 1H), 12.03 ppm (s, 1H); 13 C NMR (100 Hz, DMSO‐ d 6 , 25 °C): δ =55.6, 102.1, 112.0, 114.1, 117.3, 118.6, 119.7, 121.4, 121.7, 123.6, 125.1, 125.3, 128.5, 131.9, 133.6, 135.8, 153.5 ppm.…”