Synthesis of Imidazo[1,2-f]phenanthridines by Recyclable Magnetic MOF-Catalyzed Coupling and Cyclization of 2-(2-Bromoaryl)imidazoles with Cyclohexane-1,3-diones Followed by Aromatization

Abstract

2-(2-Bromoaryl)imidazoles react with cyclohexane-1,3-diones in the presence of a catalytic amount of recyclable Fe 3 O 4 @SiO 2 @MOF-199 and a base to give the corresponding C–C coupled and cyclized products 6,7-dihydroimidazo[1,2- f ]phenanthridin-8(5 H )-ones in high yields. The magnetic MOF catalyst could be easily recovered and reused four times without any significant loss of catalytic activity. The coupled and cyclized scaffolds were aromatized to imidazo[1,2- f ]phenanthridines in high yields by a one-pot sequential procedure including reduction, dehydration, and oxidation. The present protocol could be applied to the synthesis of Zephycandidine A, which is known to exhibit anti-tumor activity.

Synthesis of benzo[4,5]imidazo[1,2‐a]indolo[1,2‐c]quinazolines from 2‐(2‐bromoaryl)indoles and 2‐methoxybenzimidazoles under recyclable magnetic MOF‐199 catalysis

“…[ 16 ] It is known that MOF‐199 was used as an efficient heterogeneous catalyst for C (sp 2 )‐N coupling reactions, and such a heterogeneous catalysis may take place on an exposed copper site of the MOF‐199 catalyst. [ 17,18 ] As shown in entry 1 of Table 1, because the reaction proceeds without MOF‐199 catalyst and produces 3a even if the yield is low, the intermediate 9 can also be formed by an addition‐elimination nucleophilic aromatic substitution via Meisenheimer complexes 5 – 8 of 1a and 2a . [ 19 ] It appears that the base plays a role in neutralizing an acid produced during the reaction course.…”

Magnetic MOF‐199‐Catalyzed Synthesis of Benzo[4,5]imidazo[1,2‐f]phenanthridines and Their Analogues by Tandem C(sp2)−C Coupling and Cyclization Followed by Aromatization

“…Among them, in connection with this report, we recently reported that imidazo[1,2‐ f ]phenanthridines can be formed by recyclable magnetic MOF‐199‐catalyzed C( sp 2 )−C coupling and cyclization of 2‐(2‐bromoaryl)imidazoles and cyclohexane‐1,3‐diones, followed by aromatization (Scheme 1). [16c] This work started during the course of the extension of such a protocol to synthesize other N‐fused heterocycles. Herein, we describe another route for the synthesis of benzo[4,5]imidazo[1,2‐ f ]phenanthridines by C( sp 2 )−C coupling and cyclization between 2‐(2‐bromoaryl)benzimidazoles and cyclohexane‐1,3‐diones under reusable magnetic MOF‐199 catalysis and subsequent aromatization (Scheme 1).…”

Platinum-Catalyzed Hydrative Dimerization of Alkynylsilanes to α,β-Unsaturated Ketones

“…The deoxygenative aromatization of 6 to 1-arylnaphthalenes 8 was achieved by a four-step method, including a DDQ oxidation. 10 When the PtCl 2 -catalyzed reaction of 1p with water was conducted in the absence of CuCl and LiCl, a white precipitate ( 9) was formed along with a small amount of 2p (21% yield). 1 H and 13 C NMR spectra of 9 showed the presence of a cyclohexylacetyl group, and a broad proton signal appeared at 18.4 ppm.…”

“…The I 2 -promoted etherification/aromatization of 6 effected the efficient synthesis of 1-aryl-3-methoxynaphthalenes 7 . The deoxygenative aromatization of 6 to 1-arylnaphthalenes 8 was achieved by a four-step method, including a DDQ oxidation …”