Trimethyl(prop-1-ynyl)silane (4 mL, 28 mmol) and N,N,N′,N′-tetramethylethanediamine (5 mL, 36 mmol) were dissolved in dry diethyl ether (50 mL) and cooled to −78° C. Tert-butyllithium, 1.7 M solution in pentane (17 mL, 28 mmol) was added dropwise and the heterogenous solution was allowed to warm to 0° C. for 15 min to give a clear yellow solution, which was recooled to −78 C. Azeotropically (S,E)-N—((S)-2,3-bis(tert-butyldimethylsilyloxy)propylidene)-2-methylpropane-2-sulfinamide (3.0 g, 7 mmol) in dry THF (20 mL) was added dropwise and the solution was stirred for 1 h until the starting material was consumed. The reaction mixture as quenched with NH4Cl and extracted with EtOAc. The combined organics were washed with water, brine, dried over Na2SO4, filtered, and concentrated to afford a yellow oil as (S)—N-((2S,3S)-1,2-bis(tert-butyldimethylsilyloxy)-6-(trimethylsilyl)hex-5-yn-3-yl)-2-methylpropane-2-sulfinamide.
