One-pot reactions of thioformates with lithium silylacetytides, arylmagnesium halides, and electrophiles that produce propargyl (2-propynyl) sulfides are described. The pathway for this process begins with addition of lithium (trimethylsilyl)acetylide to the thioformate C=S carbon. This step is followed by addition of the arylmagnesium halide to the sulfur atom of the C=S group in the in situ generated propynethial. The intermediacy of the propynethial in this process was confirmed by trapping through a Diets-Alder reaction with cyclopentadiene.