Diisopropylamine → 1,2,3,4-Tetrahydro-1,1,4,4,6-pentamethylnaphthalene

Participants

Reaction Conditions

Reaction Steps

To a stirred solution of 794.2 mg (7.8486 mmol) diisopropylamine in 7 ml dry tetrahydrofuran under argon at -78° C. was added dropwise 4.9 ml of 1.6M (7.84 mmol) n-butyllithium in hexane. This solution was stirred at -78° C. for 1.25 hours and then treated via a double ended needle with a solution of 1.9 g (7.7749 mmol) of 1,1,4,4,7-pentamethyl-6-acetyl-1,2,3,4-tetrahydronapthalene in 4 ml dry tetrahydrofuran. After stirring at -78° C. for 1 hour, the mixture was treated with 1.3134 g (7.6117 mmol) of diethyl chlorophosphate. The cooling bath was removed and mixture stirred at room temperature for 3 hours. This material was then transferred using a double ended needle into a solution of lithium diisopropylamide [prepared as above using 1.5884 g (15.6972 mmol) of diisopropylamine and 10 ml of 1.6M (16 mmol) n-butyllithium in hexane] in 15 ml dry tetrahydrofuran at -78° C. The cooling bath was removed and mixture stirred at room temperature for 15 hours, then quenched with 50 ml water, and acidified to pH 1 with 3N hydrogen chloride. The mixture was extracted with 3×75 ml petroleum ether and the organic extracts were combined, washed with saturated NaHCO3 and saturated NaCl solutions and dried (MgSO4). Solvent was then removed in vacuo and the residue purified by flash chromatography (silica; 3% ethyl acetate in hexane) followed by kugelrohr distillation (50° C., 0.05 mm) to give the title compound as a colorless oil. PMR (CDCl3): δ1.28 (12H, s), 1.67 (4H, s), 1.42 (3H, s), 3.20 (1H, s), 7.15 (1H, s), 7.44 (1H, s).

Provenance & Evidence