A mixture of 3-(dimethylamino)-1-[6-(3-methoxyphenyl)imidazo[2,1-b][1,3]thiazol-5-yl]prop-2-en-1-one (5.0 g, 15.3 mmol) and tert-butyl (3R)-3-{[(Z)-amino(imino)methyl]amino}piperidine-1-carboxylate hydrochloride (5.28 g, 18.95 mmol) is diluted with 60 ml of absolute ethanol and treated with 1.15 eq. of a 21% w/w solution of sodium ethoxide in ethanol (6.56 ml) to form a reaction mixture. The reaction mixture is heated to reflux for 24 hours. Volatiles are removed in vacuo and the residue is taken up in 250 ml of ethyl acetate and 250 ml of water. The phases are separated and the aqueous phase is extracted with 250 ml of ethyl acetate. The combined organic extracts are washed with 250 ml each of water, and then with a saturated sodium chloride solution (250 ml). The organic phase is dried with magnesium sulfate, filtered and concentrated in vacuo, to give a yellow oil. The product is purified by flash chromatography on silica gel (ethyl acetate/hexanes, 50%) to yield 7.2 g of a pale yellow solid (93%). 300 MHz 1H NMR (DMSO-d6 at 80° C.) δ: 8.69 (d, J=3.5 Hz, 1H), 8.10 (d, J=5.3 Hz, 1H), 7.32-7.41 (m, 2H), 7.12-7.18 (m, 2H), 6.91-7.02 (m, 2H) 6.41 (d, J=5.3 Hz, 1H), 3.94 (br. d, J=7.0, 1H), 3.74-3.88 (m, 1H), 3.78 (s, 3H), 3.67 (br. d, J=13.2, 1H), 2.86-3.02 (m, 2H), 1.90-2.06 (m, 1H), 1.70-1.84 (m, 1H), 1.38-1.64 (m, 2H), 1.34 (s, 9H). LCMS: 507 [M+H].
