Synthesis
In a flame-dried Schlenk tube (fitted with a PTFE plug valve), 1.2 mmol (0.127 g) of pivaloyl chloride (2a) was added to a stirred mixture of 1.0 mmol (0.402 g) of tributyl(3-methylphenyl)tin (1f) and 1.0 mmol (0.148 g) of indium powder. After purging the system with nitrogen through three evacuation-nitrogen filling cycles, the Schlenk tube was sealed and immersed in a water-detergent bath at 60°C. An ultrasonic titanium probe was inserted into the bath 10 mm from the bath wall and 5 mm from the bottom of the Schlenk tube, and ultrasound was applied in pulsed mode (duty cycle = 70%; output power = 70%) for 10 min. Subsequently, 10% (m/v) NaOH solution (2 mL) and 10 μL of tetradecane (internal standard) solution were added, and the mixture was stirred at room temperature for 15 min and then diluted with dichloromethane (5 mL). After stopping stirring for about 5 min, the supernatant was poured into a dispensing funnel.The silver-white solid precipitate at the bottom of the Schlenk tube was washed with acetone (2 × 5 mL) and deionized water (2 × 5 mL) and then dried under vacuum at room temperature. The dried sample (0.133 g) was shown to be pure indium by DSC analysis with a recovery of 90%. The organic phase was washed sequentially with water and brine, dried with anhydrous sodium sulfate, filtered, analyzed by GC, and then concentrated under vacuum. Finally, it was analyzed by silica gel column chromatography (60 , 70-230 mesh, with 10% KF-doped hexane/dichloromethane 8:2 as eluent) purified to give 0.096 g (53%) of 3',2,2-trimethylpropiophenone (3fa) as a colorless oil.
References
[1] Journal of Organometallic Chemistry, 2009, vol. 694, # 22, p. 3674 - 3678
[2] Ultrasonics Sonochemistry, 2013, vol. 20, # 3, p. 826 - 832
