P-Toluenesulfonyl bromide

To 4.24 g (25.8 mmol) of monosilylated diyne 30 in 110 mL of dry THF was added dropwise, under a nitrogen atmosphere, 11 mL (28 mmol) of 2.5 M H-butyUithium in hexane at — 78°C. The mixture was stirred for 30 min, then 7.12 g (30.3 mmol) of p-toluenesulfonyl bromide in 30 mL of THF was added over a 10 min period. The solution was stirred for 30 min at — 78 °C and at room temperature for 1 h. Next, 150 mL of water was added. The layers were separated, and the aqueous layer was extracted with 3 x 50 mL of pentane. The combined extracts were washed with 150 mL each of 10% aqueous sulfuric acid, saturated aqueous sodium bicarbonate, and water, dried over magnesium sulfate, and concentrated under reduced pressure. Column chromatography on silica gel with 10 1 hexane/ethyl acetate gave 4.90 g (76%) of bromoalkyne 50 as a colorless liquid that was 90% pure by GC (contaminants were not characterized). It is not advisable to purify the product by distillation due to the possibility of explosive decomposition - CAUTION [44] ... 

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