4-Iodoaniline → 1-Azido-4-iodobenzene

4-Iodoaniline (32, 6.00 g, 27.4 mmol) was dissolved in 25 mL TFA and stirred in ice bath. Solid NaNO2 (2.07 g, 30.1 mmol) was added in small portions. The resulting mixture was stirred for 30 min in the ice bath. Sodium azide (1.87 g, 28.8 mmol) was dissolved in 10 mL water and chilled in ice bath. This cold solution was then added to the TFA solution in three portions. The mixture was stirred in ice bath for 1 hr and concentrated in vacuo to remove TFA. The residue was taken into 600 mL DCM and washed with water three times. The organic phase was dried using MgSO4 and concentrated in vacuo to afford 1-azido-4-iodobenzene 33 as a brownish waxy solid in >99% yield. In the mean time, 5-chlorothiophene-2-carboxylic acid (4, 9.13 g, 56 mmol) was dissolved in 200 mL dry DCM along with 0.5 mL dry DMF. To the vigorously stirred solution was carefully added oxalyl chloride (14.7 mL, 169 mmol) dropwise. The resulting solution was stirred for 3 hrs at RT and concentrated in vacuo. The residue was pumped to dryness and then dissolved in 300 mL dry DCM. To this solution was added propargylamine (5.8 mL, 84 mmol) dropwise. The mixture was stirred at RT for overnight and a lot of solid precipitated out. To this mixture was added 600 mL hexane. The mixture was vigorously stirred for a few hours and filtered for the solid (product 34). The solid (9.47 g, 85%) was washed with hexane and was pure enough for direct use without further purification. MS found for C8H6ClNOS as (M+H)+ 200.0, 202.0.