Trimethylsilylacetylene → Ethyl 8-trimethylsilylacetylenyl-6-phenyl-4H-benzo[f]imidazo[1,5-a][1,4]diazepine-3-carboxylate

Participants

Reaction Steps

A mixture of bromide 5 (0.3 g, 0.73 mmol), trimethylsilylacetylene (0.143 g, 1.46 mmol) and bis(triphenylphosphine)-palladium-(II) acetate (55 mg, 0.073 mmol) in a mixed solvent system of toluene (20 mL) and anhydrous TEA (50 mL) was heated to reflux under argon. See, Liu, et al., 1996; Austin, et al., 1981; Heck, 1985. After stirring for 12 hours at reflux, the mixture was cooled to room temperature and the precipitate which formed was removed by filtration. The filtrate was concentrated under reduced pressure and the residue was treated with a saturated aqueous solution of NaHCO3 (20 mL), and extracted with CHCl3 (3×25 mL). The combined extracts were washed with brine and dried (Na2SO4). After removal of solvent under reduced pressure, the residue was purified by flash chromatography (silica gel, EtOAc) to afford 6 (XLiXHeII-048) as a white solid (0.29 g, 93%). This benzodiazepine can also be obtained from 2 in 45% yield by following the same procedure 6 (XLiXHeII-048): mp: 170-172° C.; IR (KBr) 2958, 2152, 1718 cm−1; 1H NMR (CDCl3) δ 0.23 (s, 9H), 1.42 (t, 3H, J=7.2 Hz), 4.04 (d, 1H, J=12.6 Hz), 4.41 (m, 2H, J=7.2 Hz), 6.23 (d, 1H, J=12.6 Hz), 7.35-7.55 (m, 7H), 7.73 (dd, 1H, J=8.3 Hz and 1.9 Hz), 7.93 (s, 1H); MS (EI) m/e (relative intensity) 427 (M+, 76), 412 (5), 381 (55), 353 (100) 303 (10), 287 (7). Anal. Calcd. for C25H25N3O2Si.⅓EtOAc: C, 69.22; H, 6.01; N, 9.20. Found: C, 68.87; H, 5.81; N, 9.37.

Provenance & Evidence