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Synlett 2012; 23(9): 1353-1357
DOI: 10.1055/s-0031-1290979
DOI: 10.1055/s-0031-1290979
letter
Microwave-Assisted Metal-Free Synthesis of 2,8-Diaryl-6-aminoimidazo-[1,2-a]pyridine via Amine-Triggered Benzannulation
Further Information
Publication History
Received: 16 February 2012
Accepted after revision: 22 March 2012
Publication Date:
14 May 2012 (online)
Abstract
An efficient microwave-assisted metal-free amino benzannulation of aryl(4-aryl-1-(prop-2-ynyl)-1H-imidazol-2-yl)methanone with dialkylamines afforded a variety of 2,8-diaryl-6-aminoimidazo[1,2-a]pyridine in moderate to excellent yield.
Supporting Information
- for this article is available online at http://www.thieme-connect.com/ejournals/toc/synlett.
- Supporting Information
-
References and Notes
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- 21 General Procedure for the Preparation of 2,8-Diaryl-6-aminoimidazo[1,2-a]pyridine (5) A mixture of 4-aryl-2-aryloyl-1-(prop-2-ynyl)-imidazole 3 (0.4 mmol), secondary amine 4 (2.0 mL), and 4 Å MS (200 mg) taken in a 10 mL closed microwave vial was subjected to microwave irradiation power of 120 W 80 °C for 10 min. Completion of the reaction was confirmed by TLC. After removing the excess base, the residue was purified by column chromatography using PE and EtOAc mixture (90:10) to yield 5. Spectroscopic Data for Compound 5a Compound 5a was isolated as pale green color solid; mp 140–142 °C. IR (KBr): 1626, 1477, 1392, 1240, 711 cm–1. 1H NMR (300 MHz, CDCl3): δ = 2.02 (t, J = 6.3 Hz, 4 H), 3.27 (t, J = 6.3 Hz, 4 H), 6.98 (d, J = 1.8 Hz, 1 H), 7.23–7.28 (m, 2 H), 7.36–7.52 (m, 5 H), 7.77 (s, 1 H), 7.95 (dd, J = 7.8, 1.2 Hz, 2 H), 8.15 (dd, J = 7.8, 1.2 Hz, 2 H). 13C NMR (75 MHz, CDCl3): δ = 25.2, 48.3, 104.3, 108.5, 115.9, 125.8, 127.2, 127.9, 128.2, 128.4, 129.1, 129.5, 134.6, 136.9, 137.3, 140.7, 144.7. LC–MS [M + 1]: m/z = 340.42. Anal. Calcd for C23H21N3: C, 81.38; H, 6.24; N, 12.38. Found: C, 81.18; H, 6.16; N, 12.24
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