p-Bromochlorobenzene → 4-(azetidin-1-yl)-5-[5-(4-chlorophenyl)-1-methyl-1H-pyrazol-4-yl]-7-methylimidazo[5,1-f][1,2,4]triazine

Participants

Reaction Steps

4-(Azetidin-1-yl)-7-methyl-5-(1-methyl-1H-pyrazol-4-yl)imidazo[5,1-f][1,2,4]triazine (10.0 g, 37.1 mmol), 1-bromo-4-chlorobenzene (14.2 g, 74.2 mmol), freshly ground potassium carbonate (15.4 g, 111 mmol) and allylpalladium(II) chloride dimer (970 mg, 2.60 mmol) were combined in a reaction flask; the flask was then evacuated under vacuum and flushed with nitrogen. 1,4-Dioxane (180 mL) was added, and the reaction was stirred at room temperature. The mixture was degassed under vacuum, and nitrogen was bubbled through it for 5 minutes. The evacuation-nitrogen purge procedure was repeated an additional two times. The reaction was heated to 100° C. for 72 hours, then cooled to room temperature and combined with an identical reaction carried out on 5.0 g of 4-(azetidin-1-yl)-7-methyl-5-(1-methyl-1H-pyrazol-4-yl)imidazo[5,1-f][1,2,4]triazine. The combined reaction mixtures were concentrated in vacuo, and after suspension in ethyl acetate, the residue was applied to a pad of silica gel topped with Celite. The pad was eluted with ethyl acetate (1.5 L) followed by a 9:1 mixture of ethyl acetate/methanol (1 L). The combined eluants were concentrated in vacuo to provide an oil (25 g), which was dissolved in ethyl acetate (500 mL) and extracted with aqueous hydrochloric acid (1 M, 300 mL). The aqueous layer was basified with aqueous 1 M sodium hydroxide solution, and extracted with ethyl acetate (2×250 mL). The two organic layers were combined and washed with aqueous citric acid (1 M, 200 mL), and the aqueous citric acid layer was extracted with ethyl acetate (8×100 mL). The combined organic layers were then washed with a 1:1 mixture of saturated aqueous sodium bicarbonate solution/saturated aqueous sodium chloride solution, dried over magnesium sulfate, filtered and concentrated under reduced pressure. The resulting solid was stirred in a hot mixture of heptane (˜100 mL) and ethyl acetate (˜15 mL), cooled to room temperature and stirred for 16 hours. The solid was isolated via filtration to provide a white powder (10.6 g). To remove residual palladium (0.3% by QTI Analytical Services analysis), this material was dissolved in a mixture of ethyl acetate (100 mL) and 2-methyltetrahydrofuran (150 mL) at room temperature and treated with SiliaBond® thiol (SiliCycle, 1.35 mmol/g, 5 g, 6.75 mmol of activity). The mixture was stirred for 20 hours, then filtered through Celite. The filtrate was treated with Darco® activated carbon (500 mg) and stirred for 15 minutes before being filtered and concentrated under reduced pressure. The resulting oil was azeotroped with a 1:1 mixture of heptane and ethyl acetate to provide a white solid (9.9 g), which was triturated with a mixture of heptane (80 mL) and ethyl acetate (10 mL) at reflux, then cooled to room temperature and stirred for an additional 36 hours. Filtration provided the product as a white solid. Yield: 9.48 g, 25.0 mmol, 67%. LCMS m/z 380.0 (M+1). 1H NMR (500 MHz, CDCl3) δ 2.21-2.28 (m, 2H), 2.63 (s, 3H), 3.4-4.4 (v br m, 4H), 3.90 (s, 3H), 7.31-7.36 (m, 4H), 7.64 (s, 1H), 7.80 (s, 1H).

Provenance & Evidence