1,4,7-Triazacyclononane trihydrochloride

synthetischeSynthesis of 1,4,7-Triazacyclononane trihydrochloride (tacn.3HCl) A round bottom flask (1 L) was charged with 18M H2SO4 (450 mL) and 1,4,7-tris(p-toluenesulfonyl)-1,4,7-triazacyclononane (4) (138.8 g, 0.234 mol) added in small portions (approximately 10 g every 5 min). The mixture was heated with stirring in a heat block for 3 days at 120°C. The resulting black solution was cooled to room temperature and added dropwise using a dropping funnel to a vigorously stirred mixture of cold absolute EtOH/Et2O (1.5 L/900 mL) cooled in an ice bath. An overhead stirrer was used to ensure efficient stirring. A sticky hygroscopic brown/grey precipitate formed, which was isolated quickly by vacuum filtration and immediately dissolved in de–ionised H2O (1 L). The mixture was heated for 2 h at 60°C. The mixture was then cooled to room temperature, filtered through Celite and the resulting solution concentrated to 250 mL under reduced pressure at 65°C. Conc. HCl (200 mL) was added followed by absolute EtOH until the solution became cloudy. The mixture was stored at 4°C overnight to promote precipitation. The white precipitate was collected by filtration and washed with ice cold absolute EtOH (3 x 50 mL), followed by Et2O (2 x 50 mL) to yield tacn.3HCl (5) as a white crystalline powder. Yield 44.9 g (80%).mp. 268.1–270.0°C (Lit.4 mp. 280–281°C). 1H NMR (300 MHz, D2O) δH 3.48 (12H, s, CH2). 13C NMR (75 MHz, D2O) δC 43.1 (CH2). ESI–MS m/z [M + H]+ 130.1. The 1H and 13C NMR spectral data were consistent with literature data.Using iSUSTAIN(TM) to validate the chemical attributes of different approaches to the synthesis of tacn and bridged bis(tacn) ligands