A. p-Tolyl 2-(trimethylsilyl)ethynyl sulfone. In a flame-dried, <500-mL>, three-necked, round-bottomed <flask> fitted with a nitrogen inlet and glass stoppers are placed 200 mL of dry dichloromethane (Note 1) and 29.4 g (0.22 mol) of freshly powdered anhydrous aluminum chloride. After the addition of p-toluenesulfonyl chloride (41.9 g, 0.22 mol), the resulting dark-brown mixture is <shaken> occasionally for <20 min> at <room temperature>.
A 1-L, three-necked, round-bottomed flask equipped with a 500-mL addition funnel and a Teflon-coated stirring bar is <flame-dried> under a stream of <dry nitrogen>. The <flask> is <charged> with bis(trimethylsilyl)acetylene (34.0 g, 0.20 mol) (Note 2) and <dry dichloromethane> (200 mL) (Note 1) and the <solution> is <cooled> to <0°C> in an <ice–water bath>.
The p-toluenesulfonyl chloride–aluminum chloride complex is quickly <filtered> through a <glass wool plug> (Note 3) into the <addition funnel>. The residue is <washed> rapidly with an additional <50 mL> of dry dichloromethane and the funnel is quickly stoppered. The complex is added dropwise during <1 hr> to the cold (0°C), magnetically <stirred> <silylacetylene solution>. On completion of the addition, the reaction mixture is allowed to <warm> to <room temperature> and is <stirred> for an additional <12 hr>. The mixture is <hydrolyzed> by pouring it into a slurry of 20% hydrochloric acid (200 mL) and ice (200 g) (Note 4). The <organic layer> is <separated>, <washed> twice with <water> (150 mL), and <dried> over <anhydrous sodium sulfate>. Removal of solvent in a <rotary evaporator> gives a brown solid (Note 5) that is <recrystallized> from light petroleum ether (bp 40–60°C) to yield 39.7–40.4 g (79–80%) of p-tolyl 2-(trimethylsilyl)ethynyl sulfone as white crystals, mp 81–82°C (Note 6).