Iron-Mediated One-Pot Synthesis of 3,5-Diarylpyridines from β-Nitrostyrenes

Abstract

An operationally simple and mild one-pot protocol for the synthesis of a variety of 3,5-diarylpyridines from β-nitrostyrenes was achieved by using elemental iron. This reaction proceeds via reduction of the nitro group, resulting in in situ imine formation followed by trimolecular condensation with concomitant debenzylative aromatization. By employing this method, a series of symmetrical and unsymmetrical 3,5-diarylpyridines were synthesized with good to excellent yields. In addition, this method was also utilized for the synthesis of Sch-21418, an anti-inflammatory agent on gram scale.

The Synthesis of 3‐Arylquinolines from o‐Nitrobenzaldehydes and β‐Nitrostyrenes via an Iron‐Promoted Reductive Cyclization

“…On the basis of the above results and previous reports, a possible mechanism was proposed as outlined in Scheme ( 3 a as an example). Initially, Fe acted as a reducing agent promoting 1 a to form intermediate o ‐aminobenzaldehyde 5 .…”

Two C═C Bond Participation in Annulation to Pyridines Based on DMF as the Nonadjacent N and C Atom Donors

“…. 16 Compound 3e was synthesized on the basis of general procedure 1 and purified by column chromatography with PE/EA = 20:1 as the eluent: 48.81 mg, 68% yield, white solid; 1 H NMR (400 MHz, chloroform-d) δ 8.80 (s, 2H), 8.04 (s, 1H), 7.57 (d, J = 8.1 Hz, 4H), 7.34 (d, J = 8.5 Hz, 4H), 2.73 (q, J = 7.6 Hz, 4H), 1.30 (t, J = 7.6 Hz, 6H); 13 C{H} NMR (101 MHz,144.5,136.7,135.1,132.7,128.6,127.2,28.6,15.5; m/z (GC−MS) = 287.…”

“…3,5-Bis(2-fluorophenyl)pyridine (Scheme 2, 3i, Known Compound).. 14,16 Compound 3i was synthesized on the basis of general procedure 1 and purified by column chromatography with PE/EA = 20:1 as the eluent: 40.71 mg, 61% yield, yellow solid; 1 H NMR (400 MHz, 3,5-Bis(3-fluorophenyl)pyridine (Scheme 2, 3j, Known Compound).. 14,15 Compound 3j was synthesized on the basis of general procedure 1 and purified by column chromatography with PE/EA = 20:1 as the eluent: 39.38 mg, 59% yield, white solid; 1 H NMR (400 MHz, chloroform-d) δ 8.82 (d, J = 2.2 Hz, 2H), 8.00 (t, J = 2.2 Hz, 1H), 7.51−7.38 (m, 4H), 7.36−7.30 (m, 2H), 7.17 3,5-Bis(4-fluorophenyl)pyridine (Scheme 2, 3k, Known Compound).. 13−16 Compound 3k was synthesized on the basis of general procedure 1 and purified by column chromatography with PE/EA = 20:1 as the eluent: 44.73 mg, 67% yield, white solid; 1 H NMR (400 MHz, δ 8.80 (s, 2H), 7.97 (s, 1H), 7.59 (dd, J = 8.5, 5.4 Hz, 4H), 7.19 (t, J = 8.5 Hz, 4H); 13 C{H} NMR (101 MHz,J = 248.3 Hz),146.4,135.8,133.6,132.8,128.9 (d,J = 8.2 Hz),116.2 (d,J = 21.7 Hz); m/z (GC−MS) = 267.…”

Visible light-mediated intermolecular [2 + 2] photocycloaddition of 1-aryl-2-nitroethenes and olefins

“…A colour change of the refluxing solution indicated a successful elimination of the intermediate alcohol to the nitroethene which was isolated exclusively as the trans-isomer. Only the 2-thiophenyl product 1e was not accessible by this method and required the use of a stronger base (NaOH in MeOH) 15 to induce the Henry reaction.…”