Example 2 Preparation of tert-butyl (3-iodothiophene-2-yl)carbamate: 3-iodothiophene-2-carboxylic acid (23.5 g, 0.10 mol) was mixed with triethylamine (15 mL, 1.1 eq.) to which was added a tert-butanol solution of diphenoxyphosphoryl azide (30 g, 1.1 eq.). The reaction mixture was heated at reflux temperature for 16 h and subsequently cooled to room temperature. The reaction mixture was washed with saturated Na2CO3 solution and extracted with EtOAc. The organic extracts were combined, dried with MgSO4 and concentrated under reduced pressure. The resulting residue was purified by column chromatography (eluent: 10% EtOAc in hexane solution) to give the title product as a brown solid (10.5 g, 35% yield). The product was characterized by HPLC and mass spectrometry.
