General ExperimentalMelting points were determined in open capillary tubes on Gallenkamp (England) melting point apparatus and are uncorrected. IR spectra were recorded on a Shimadzu FTIR spectrophotometer. 1 H NMR and 13 C NMR spectra were recorded on a Bruker DPX-400 spectrophotometer (400MHz) and Bruker DPX-500 spectrophotometer (500MHz) using tetramethylsilane as internal reference. Analytical thin-layer chromatography (TLC) was performed on precoated silica gel 60F-254 (E. Merck), and the spots were visualized with UV light. Column chromatography was performed on silica gel (60-120 mesh). Bis(triphenylphosphine)palladium(II)chloride and other reagents were purchased from E. merck (Germany) and Fluka (Switzerland).
Synthesis of 2-iodonitrobenzene20: 2-Nitroaniline 19 5.0 g (36.0 mmol) was stirred with 7.5 g (4.10 mL) of conc. H 2 SO 4 and 40 ml of water for 1 hour. The mixture was cooled in a freezing point (0-5°C) and was stirred mechanically. A solution of 2.5 g (36.0 mmol) of sodium nitrite in 7.5 mL of water was added to the mixture. The filtrate was poured into an ice cooled solution of 10 g (60.0 mmol) potassium iodide in 30 mL water with stirring. The precipitate formed was collected by filtration under reduced pressure and washed with water and finally dried & recrystallized from ethanol. Yellow solid, mp 48-49°C, IR (KBr): max 1581.7, 1517 (C=C), 1470(Ar-NO 2 ), 1330.2, 1296.0, 779, 723 cm -1 ; 1 H NMR (500 MHz, CDCl 3 ): 8.04 (d, 1H, J = 8.3 Hz, H-3), 8.01 (d, 1H, J =7.5 Hz, H-6), 7.85 ( t, 1H, J =7.5 Hz, H-4) and 7.60 (t, 1H, J =7.5 Hz, H-5).
Synthesis of 2-iodoaniline 21:In a 250 mL round bottom flask, equipped with a reflux condenser, a mixture of 5 g (20.0 mmol) of 2 -iodonitrobenzene 20, 3.92 g (70.0 mmol) of granulated iron were stirred and then the mixture of 4.7 g (8 mL) of glacial acetic acid and 80 mL ethanol were poured one by one into this mixture and was shaken the contents of the flask steadily. The reaction mixture was refluxed for 3 hours with constant stirring at 118°C. The reaction mixture was diluted with 100 mL water and neutralized with dil. NaOH (aq) solution. The product was separated by steam distillation and finally extracted with CHCl 3. The organic layer was washed with distilled water, dried with anhydrous
