Quinone → HCID 21292348, compound

Participants

Reaction Conditions

Reaction Steps

A solution of the product of Example 7a (9.75 g, 0.05 mole, 1.3 eq), dibromoethane (6.4 g, 0.03 mole, 0.8 eq), and 30 mL of dry THF was added over a 2.5 hr period to a slurry of 99.9% magnesium turnings (3.6 g, 0.15 mole, 3 eq) and 75 mL THF with vigorous stirring. The temperature was maintained at 24°-27° C. by external cooling. The resulting Grignard solution was then cooled to -78° C. until further use. In a separate flask, phenylacetylene (3.9 g, 0.038 mole, 1 eq) in 20 mL THF was cooled to -78° C., n-butyllithium (1.38 molar, 28 mL, 0.038 mole, 1 eq) was added via syringe, the solution stirred 30 min at -78° C., warmed to 0° C. for 30 min and cooled again to -78° C. In a separate flask, benzoquinone (4.2 g, 0.038 mole, 1 eq) in 20 mL of THF was cooled to -78° C., the phenylacetylide solution was added dropwise, resulting in a blue solution which was stirred 25 min at -78° C. DMPU (30 g, 0.23 mole, 6 eq) was added, the reaction warmed to -5° C., and the Grignard reagent solution added over about a 15 min period. The cooling bath was allowed to warm to RT and the reaction stirred overnight. The reaction mixture was quenched with 100 mL of saturated ammonium chloride solution, 100 mL of water added, the layers separated and the aqueous layer extracted with three 150 mL portions of ether. The combined organic layers were washed with water, brine and dried over anhydrous sodium sulfate. The dried solution was evaporated in vacuo to give a brown oil, 9.21 g portion of which was purified by trituration with ether followed by flash chromatography on silica gel eluting with 3:1 hexane/EtOAc to 1:1 hexane/EtOAc to yield 2.4 g of the title compound.

Provenance & Evidence