Dimethylformamide → 2-Isopropyl-5,6-dihydro-1H-benzo[d]imidazol-7(4H)-one

Participants

Reaction Conditions

Reaction Steps

To 2-bromo-3-(ethyloxy)-2-cyclohexen-1-one (160 g) was added N,N-Dimethylformamide (1000 mL) followed by 2-methylpropanimidamide hydrochloride (107 g) and potassium carbonate (151 g). The suspension was then stirred at 50° C. under nitrogen. After 2.75 hr the mixture was filtered and as much DMF as possible was evaporated off under high vacuum. The residue was partitioned between ethyl acetate (400 ml) and a minimum of aq lithium chloride (120 ml). The aqueous layer was extracted well with ethyl acetate (3×200 ml). The combined organics were washed with brine, filtered to give a small amount of a white solid and the filtrate dried (MgSO4), filtered and evaporated, including high vacuum. This was stirred with TBME (350 ml) then filtered to give a white solid, 16.27 gm. The filtrate from this was evaporated and weighed; this partly solidified overnight. Ether and cyclohexane were added to try and precipitate out more product but the solid was oily. The solution was decanted off and gave a golden oil on evaporation, 77 gm. The oily solid was evaporated: 38 gm, dissolved in DCM and purified by column chromatography (silica cartridge), eluting with 0-100% ethyl acetate in dichloromethane over 10 column volumes. Fractions were evaporated and the resulting solid slurried in ether and collected by filtration: This gave a white solid, 4.0 gm. No solid came out from the aqueous phase overnight. So it was extracted with more ethyl acetate and DCM. The organics were dried and evaporated and gave 69 gm of a beige slurry that was stirred with diethyl ether and filtered to give a white solid, 11.3 gm. The filtrate was combined with aqueous extraction solvents from a previous experiment and purified by column chromatography (silica), eluting with 0-100% ethyl acetate in dichloromethane. All product came through in fractions 1 & 2 so they were combined and washed with aq LiCl, dried and re-evaporated to a beige slurry, 46.4 gm, that was stirred in ether and filtered to give a white solid, 5.85 gm. Because all the batches were of the same purity, they were combined: This gave the title compound, a white solid, 37.42 gm.

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