Triphenylphosphine → 2-Methoxy-6-(6-methoxy-4-((2-phenylthiazol-4-yl)methoxy)benzofuran-2-yl)imidazo[2,1-b][1,3,4]thiadiazole

Participants

Reaction Conditions

Reaction Steps

A mixture of 6-methoxy-2-(2-methoxyimidazo[2,1-b][1,3,4]thiadiazol-6-yl)benzofuran-4-ol (Example 1H, 0.800 g, 2.52 mmol), triphenylphosphine (0.992 g, 3.78 mmol) and (2-phenylthiazol-4-yl)methanol (Example 3B, 0.555 g, 2.90 mmol) in a 200 mL flask fitted with an addition funnel was maintained under vacuum for ten minutes. The mixture was then flushed with nitrogen and charged with dry tetrahydrofuran (60 mL, distilled over lithium aluminum hydride). The solution was warmed to ˜50° C. and then sonicated for 5 min. The cooled heterogeneous mixture was then treated at 22° C. with a solution of diisopropyl azodicarboxylate (0.663 g, 3.28 mmol) in tetrahydrofuran (15 mL), added dropwise over 2.5 h. The reaction was homogeneous (pale yellow) at the end of the addition. The mixture was then stirred for another 2.5 h (total 5 h). The reaction mixture was then diluted with dichloromethane (400 mL), washed with saturated sodium bicarbonate (20 mL), brine and dried (anhydrous magnesium sulfate). Evaporation gave a white solid which was chromatographed on silica gel (3×12 cm, elution dichloromethane-ethyl acetate 98.5:1.5 to 97:3). The fractions were collected and evaporated to give the desired compound (1.40 g) as a white solid, contaminated with hydrazide by tlc. Crystallization in ethyl acetate (40 mL) gave the pure title material (0.838 g, 68%) as a white solid. The mother liquors (0.475 g) were chromatographed on silica gel (3×12 cm, elution dichloromethane-ethyl acetate 98.5:1.5 to 97:3) to give after crystallization from ethyl acetate (30 mL) to provide additional desired compound (0.160 g, 13%, total 81%) as a white solid. LC (Method C): 2.480 min. HRMS (ESI) calcd for C24H19N4O4S2 [M+H]+ m/z 491.0842. found 491.0865. 1H NMR (CDCl3, 400 MHz) 3.85 (s, 3H) 4.21 (s, 3H) 5.33-5.55 (m, 2H) 6.48 (d, J=1.96 Hz, 1H) 6.72 (dd, J=1.96, 0.78 Hz, 1H) 7.12 (s, 1H) 7.36-7.39 (m, 1H) 7.41-7.50 (m, 3H) 7.86 (s, 1H) 7.95-8.02 (m, 2H).

Provenance & Evidence