Hydrochloric Acid → HCID 67121322, compound

Participants

Reaction Conditions

Reaction Steps

5-bromo-2-benzofuran-1,3-dione (1 wt) was suspended in toluene (5 vol) with stirring under nitrogen. Isopropylamine (1.1 eq, 0.416 vol) was then added dropwise over 10-30 mins at such a rate as to maintain the temperature between 15-25° C. (exothermic addition). The batch was stirred for a further 30 mins at 15-25° C. once the addition was complete, before heating to reflux under Dean-Stark conditions. The batch was held at reflux for 5-8 hrs until residual 5-bromo-2-benzofuran-1,3-dione by HPLC is <1% a/a uncorrected, then the batch was concentrated atmospherically to ca 2.5 vols2. Added toluene (3 vols) and reconcentrated atmospherically to ca 2.5 vols. Batch then cooled to 55-60° C., diluted with THF (1.5 vols), and then further cooled to 15-25° C. This was added to a solution of borane-THF complex (1.0M, 4 eq, 14.1 vol) and the resultant solution was stirred at 20-30° C. for ca 30 mins. The batch was then heated to 48-52° C., and held thus for 16-24 hrs until complete by HPLC, before cooling back to 15-25° C. The reaction was quenched inversely into aqueous hydrochloric acid (2N, 9 vol) over at least 30 mins maintaining an internal temp of 15-30° C. (initially effervescent, evolves hydrogen). Once the addition was complete, the batch was heated to 60-63° C., and held thus for 1-1.5 hrs before cooling to 15-25° C. Ethyl acetate (6 vols) was added and the resultant biphase was shaken, settled and separated1. Organics back-extracted with 2N HCl (3 vols) before being discarded. The combined aqueous liquors were then neutralized to pH>12 with 40% w/v aq NaOH (approx 3.9 vols). Overlain with ethyl acetate (6 vols) then the resultant biphase was shaken, settled and separated. Aqueous back extracted with ethyl acetate (3 vols) before being discarded. The organics were combined and washed with saturated brine (2×2 vols) before being concentrated in vacuo to ca 4 vols. Ethyl acetate (8 vols) was added and the batch was reconcentrated in vacuo to ca 4 vols. Ethyl acetate (9 vols) was added and the batch was adjusted to 0±3° C. 4M HCl in dioxane (0.89 eq, 0.98 vol) was then added slowly maintaining the batch temp within the range 0±3° C. The batch was then aged within this range for 30 min before product was collected by vacuum filtration. Washed with chilled ethyl acetate (<5° C., 2×2 vols) and dried o/n in vacuo at 30° C. to constant weight.

Provenance & Evidence