Trifluoroacetic acid → 2-[4-(2-Diisopropylamino-ethoxy)-3-methoxy-phenyl]-2,3-dihydro-isoindol-1-one

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Reaction Steps

A solution of 5-bromo-2-[4-(2-diisopropylamino-ethoxy)-3-methoxy-phenyl]-isoindole-1,3-dione [Example A1] (66 mg, 0.14 mmol) was dissolved in THF (ml) and treated with sodium borohydride (5.2 mg, 0.14 mmol). After stirring for 2 hours, the mixture was treated with isopropanol, stirred for a further 1 h then treated with acetic acid (2 drops) and stirred for 16 h at RT. The solvent was removed and the residue purified by flash chromatography to give an approximately 1:1 mixture of the 5- and 6-bromo substituted isomers of 2-[4-(2-diisopropylamino-ethoxy)-3-methoxy-phenyl]-3-hydroxy-2,3-dihydro-isoindol-1-one (37 mg). This material was dissolved in dichloromethane (2 ml) and treated with triethylsilane (1 ml) and trifluoroacetic acid (0.5 ml). The mixture was stirred at RT for 16 hours, the solvents were removed in vacuo and the residue purified by flash chromatography on silica gel (eluting with methanol-dichloromethane-aq. ammonia) to obtain 2-[4-(2-diisopropylamino-ethoxy)-3-methoxy-phenyl]-2,3-dihydro-isoindol-1-one as an approximately 1:1 mixture of 5- and 6-bromo isomers (33 mg). A solution of this material in benzene (5 ml) was treated with aqueous sodium carbonate (2M, 1 ml), ethanol (1 ml), phenylboronic acid (9 mg, 0.07 mmol) and tetrakis(triphenylphosphine)palladium[0] (10 mg) and the mixture heated to reflux for 16 h. The less dense phase was decanted, filtered through filter-aid (washing with dichloromethane), the filtrate evaporated and purified by flash chromatography on silica gel (eluting with dichloromethane-methanol-aq. ammonia) and reverse phase preparative chromatography (aq. MeCN, TFA) to give the title compounds as an approximately 1:1 mixture of isomers as their TFA salts;

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