Synthesis of 2‐Substituted Furo[2,3‐b]‐ and Furo[3,2‐c]quinolines via Heterogeneous Palladium‐catalyzed Heteroannulation

Abstract

Furoquinoline scaffolds are one of the important heterocycles and their analogues are found not only in nature 1 but also in pharmacological and biological materials, whose properties include anti-inflammatory, 2 TLR8 (Toll-like receptor-8) agonistic, 3 anti-cancerous, 4 a protein inhibitory, 5 and antimicrobial activity. 6 Owing to their diverse biological activities, there have been great efforts to extract 7 or synthesize furoquinolines, i.e., [3 + 2] cyclization reaction for furo [2,3-b]quinolines, 8 [4 + 2] cycloaddition of imines with enol ethers, 9 and a three component reaction of 4-hydroxyquinolin-2(1H)-one, aromatic aldehyde and isonitrile, and so on. 10 Recently we have paid much attentions to develop green and practical synthetic methods for synthesizing various furoheterocycles 1-6 as shown in Scheme 1. 11 The isomeric 2-substituted furopyridines such as furo[3,2b]-, furo[2,3-b]-, and furo[3,2-c]pyridine were synthesized starting from o-halohydroxypyridines and terminal alkynes catalyzed by commercial Pd/C under copper-and ligandfree conditions. Also we were able to show diversification of our protocol to make 2,3-disubstituted furoquinolines, 5 and 6, by Suzuki and Heck reactions, respectively. 11a As a part of our continuing organometallic studies on diversification of nitrogen-containing biologically active heterocycles, we attempted to synthesize furo[2,3-b]-and furo[3,2-c]quinolines starting from o-halohydroxyquinolines and terminal alkynes with heterogeneous Pd(OAc) 2 catalyst, which was supported by nanosized pore carbon ball. The best reaction condition was obtained under CNB-Pd(OAc) 2

Solvent-free hydrogenation of cyclohexene over Rh-TUD-1 at ambient conditions

“…These peaks can be attributed to the formation of b-Rh 2 O 3 phase (JCPDS 76-0148). 22 Aer reduction, Rh-0.5 pattern exhibited only peaks at 41.16 , 47.86 , and 70.17 2q. These peaks are corresponding to the crystal planes of (111), (220), and (220), respectively, which indicating the presence of metallic rhodium (Rh 0 ) particles (JCPDS 05-0685).…”

A Novel Frameshifting Inhibitor Having Antiviral Activity against Zoonotic Coronaviruses

“…Of that group, compound KCB261770 showed the most promising inhibitory effects (IC 50 = 0.07 μM, CC 50 = 18.5 μM) and was chosen for further study ( Figure 2 B,C). Compound KCB261770, 2-(5-acetylthiophen-2yl)furo [2,3- b ]quinoline, is a newly synthesized furo[2,3- b ]quinoline with a molecular weight of 294.3 [ 30 ]. Although furo-quinoline occurs naturally [ 31 , 32 ], diverse furo-quinoline derivatives have also been synthesized [ 30 , 33 ] owing to their pharmacological and biological properties including anti-inflammatory [ 34 , 35 ], anti-malarial [ 36 ], and antimicrobial activities [ 37 ].…”

“…Compound KCB261770, 2-(5-acetylthiophen-2yl)furo [2,3- b ]quinoline, is a newly synthesized furo[2,3- b ]quinoline with a molecular weight of 294.3 [ 30 ]. Although furo-quinoline occurs naturally [ 31 , 32 ], diverse furo-quinoline derivatives have also been synthesized [ 30 , 33 ] owing to their pharmacological and biological properties including anti-inflammatory [ 34 , 35 ], anti-malarial [ 36 ], and antimicrobial activities [ 37 ]. The inhibitory effects, cell viabilities, IC 50 values, and chemical structures of the rest are shown in Figure S1 .…”

Biomolecular phase separation through theoretical and computational microscope

“…134 The Monte Carlo (MC) scheme tracks a system through probabilistic calculations using random sampling, 135 while MD simulations involve integrating Newton's equations of motion, enabling representation of the positions, velocities, and accelerations of particles as functions of time. 136 Both methods are widely used in simulations of soft matter systems, [137][138][139][140][141][142] and can be applied to biomolecular phase separation.…”