2-Bromo-1-(5-bromofuran-2-YL)ethanone

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 6-Amino-nicotinonitrile (1.19 g, 10 mmol) and 2-Bromo-1-(5-bromofuran-2-yl)-ethanone (2.66 g, 10 mmol) in ethanol (50 mL) was refluxed for 24 h. The precipitate was filtered and neutralized with aqueous NaHCO3 solution. The precipitate was filtered and dried to furnish 3a in 74% yield, mp 212-214° C. (EtOH). 1H NMR (DMSO-d6); δ 6.75 (d, J=3.6 Hz, 1H), 6.98 (d, J=3.6 Hz, 1H), 7.54 (d, J=8.4 Hz, 1H), 7.71 (d, J=8.4 Hz, 1H), 8.29 (s, 1H), 9.30 (s, 1H). 13C NMR; δ 150.5, 144.2, 137.3, 134.3, 125.4, 121.9, 117.2, 116.9, 113.9, 110.4, 109.8, 97.2. MS (m/z, rel.int.); 288 (M+, 100), 161 (8). Anal. Calcd. for 3a (C12H6BrN3O): C % 50.03, H % 2.10. Found: C % 49.97, H % 2.17. was refluxed for 24 h The precipitate was filtered The precipitate was filtered dried

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Referring now to Scheme 2, the acetate salt of 2-[5-(4-Amidinophenyl)-furan-2-yl]-5,6,7,8-tetrahydro-imidazo[1,2-a]pyridine-6-carboxamidine (7) was synthesized from 2-[5-(4-Cyanophenyl)-furan-2-yl]-imidazo[1,2-a]pyridine-6-carbonitrile (4a), through the bis-O-acetoxyamidoxime followed by hydrogenation in glacial acetic acid. Compound 4a was obtained in four steps starting with two successive brominations of 2-acetylfuran first with N-bromosuccinimide, and second with bromine to form 2-Bromo-1-(5-bromofuran-2-yl)-ethanone (2) in a moderate yield. A condensation reaction between 6-Amino-nicotinonitrile and compound 2 gave 2-(5-Bromofuran-2-yl)-imidazo[1,2-a]pyridine-6-carbonitrile (3a). A subsequent Suzuki coupling of 3a with 4-Cyanophenyl boronic acid furnished 4a in good yield. Interestingly, 2-[5-(4-Amidinophenyl)-furan-2-y]-imidazo[1,2-a]pyridine-6-carbox-amidine acetate salt (8a) was obtained from 4a, through the bis-O-acetoxyamidoxime followed by hydrogenation in a mixture of ethanol/ethylacetate. Thus, by choice of hydrogenation solvent the saturated or unsaturated imidazo[1,2-a]pyridine can be obtained.