Table 1. Optimization of reaction conditions for aza-saccharin formation^a.

Entry	Deviation from standard conditions	LCMS yield 3a, [4a] (%)b
1	None	>99 {89}c, [n.d.]
2	MTBEd	81, [7]
3	Sulfonimidoyl chloride	Degradation
4	Moc	68 {52}c, [n.d.]
5	KHMDS (2.00 equiv.) added last	6, [92]
6	LiHMDS (2.00 equiv.)	2, [95]
7	NaHMDS (2.00 equiv.)	91, [n.d.]
8	KHMDS (1.50 equiv.)	82, [n.d.]
9	KHMDS (2.50 equiv.)	84, [n.d.]

^aReaction conditions: sulfonimidoyl fluoride 1a (75.0 µmol, 1 equiv.), KHMDS (150 µmol, 2.00 equiv.), THF, −78 °C, 15 min; 2-aminopyrimidine (2a, 90.0 µmol, 1.20 equiv.), THF, −78 °C, 22 °C, 15 min.

^bLCMS yield of Entry 1 verified via NMR experiment with 1,3,5-trimethoxybenzene as internal standard.

^cIsolated yield on a 400 µmol scale.

^dKHMDS (1 M in THF) used. n.d. = not detected.