Preparation of MIDA Anhydride and Reaction with Boronic Acids.

A. MIDA Anhydride (1). A 500 mL single-necked, 24/40 round-bottomed flask equipped with a 5 x 2 cm Teflon-coated magnetic stirring bar is charged with methyliminodiacetic acid (40.0 g, 270 mmol, 1.00 equiv)(Notes 2 and 3), capped with a rubber septum and evacuated and backfilled with nitrogen via 20 G needle. Acetic anhydride (140 mL, 1.49 mol, 5.52 equiv) (Note 4) is added via syringe as a single portion to form a colorless suspension. This is immediately followed by the addition of pyridine (3.30 mL, 40.5 mmol, 0.15 eq.)(Note 5) in a single portion (Figure 1B). The flask is stirred under HO O N Me OH O