Diisopropylamine → 1,1,4,4-Tetramethyl-6-ethynyl-1,2,3,4-tetrahydronaphthalene

Participants

Reaction Conditions

Reaction Steps

To a stirred solution of 1.1572 g (11.4359 mmol) of diisopropylamine in 20 ml of dry tetrahydrofuran under argon at -78° C. was added dropwise via syringe, 7.2 ml of 1.6M (11.52 mmol) n-butyllithium in hexane. This mixture was stirred at -78° C. for 1 hour and then treated dropwise with a solution of 2.635 g (11.4391 mmol) of 1,1,4,4-tetramethyl-1,2,3,4-tetrahydro-6-acetylnaphthalene in 6 ml of dry tetrahydrofuran. After stirring at -78° C. for 1 hour, the mixture was treated with 1.97 g (11.4175 mmol) of diethyl chlorophosphate. The cooling bath was then removed and the mixture stirred at room temperature for 3.5 hours. This mixture was then transferred using a double ended needle to a solution of lithium diisopropylamide [prepared using 2.31 g (22.83 22 mmol) of diisopropylamine and 14.5 ml of 1.6M (23.2 mmol) n-butyllithium in hexane] in 60 ml of dry tetrahydrofuran at -78° C. Stirring was commenced at room temperature and continued for 20 hours. The reaction was then quenched with 50 ml water and acidified with 25 ml of 3N hydrogen chloride. Reaction product was recovered by extracting with 5×50 ml pentane. Organic extracts were combined and washed with 3N hydrogen chloride, water, saturated NaHCO3 and saturated NaCl solutions and then dried (MgSO4). Solvent was then removed and residue purified by flash chromatography (silica, 5% ethylacetate in hexane) followed by kugelrohr distillation (60° C., 0.2 mm) to give the title compound as a colorless oil. PMR (CDCl3): δ1.25 (6H, s), 1.27(6H, S), 1.66 (4H, s), 2.98 (1H, S, 7.24 (2H, s), 7.46 (1H, s).

Provenance & Evidence