Hydrochloric Acid → 2,2,4,4,7-Pentamethyl-6-ethynyl-chroman

Participants

Reaction Conditions

Reaction Steps

To a solution of 455 mg (4.5 mmol) of disopropylamine in 5 ml of dry THF at -78 degrees C. was added under argon 3 ml of 1.5 M n-BuLi in hexane. The mixture was stirred at -78 degrees C. for a further 45 min and then treated with a solution of 1.07 g (4.3 mmol) of 2,2,4,4,7-pentamethyl-6-acetyl-chroman (Compound 90) in 4 ml of dry THF. The reaction mixture was stirred at -78 degrees C. for 1 h and then treated with 776 mg (4.5 mmol) of diethyl chlorophosphate. The mixture was allowed to warm to room temperature and then transferred by a double-ended needle into a solution of lithium diisopropyl amide in 10 ml dry THF at -78 degrees C. which was prepared as described above using 910 mg (9.0 mmol) of diisopropylamine and 6 ml of 1.5 M (9.0 mmol) n-BuLi in hexane. The mixture was stirred at room temperature for 15 h and then poured into 10 ml of iced water The mixture was acidified to pH=2 with 10% HCl solution. The organic layer was separated and the aqueous layer extracted with pentane. The organic extracts were combined and washed successively with water, saturated NaHCO3 and saturated NaCl solutions and then dried (MgSO4). The solvent was removed in vacuo and the residue purified by Kugelrohr distillation (82 degrees C. 0.3 mm) to give the title compound as a pale yellow oil. PMR (CDCl3): δ 1.32 (6H, s), 1.34 (6H, s), 1.81 (2H, s), 2.36 (3H, s), 3.18 (1H, s), 6.64 (1H, s), 7.40 1H (s). MS exact mass, m/e 228.1520 (calcd. for C16H20O, 228.1514).

Provenance & Evidence