Treatment of 2-(2-oxo-2-arylethylthio)-N-(4H-1, 2, 4-triazol-3-yl) acetamides with paraformaldehyde in the presence of a base has led to a tandem chemoselective hydroxymethylation followed by cyclization yielding a set of novel 6-aroyl-4-(4H-triazol-3-yl) thiomorpholin-3-ones. The thiomorpholine ring has been found to have a boat like conformation in these compounds as evidenced by NOESY NMR spectrum.