REFERENCES
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- Modified experimental procedure for 2: to a stirred solution of 1 (4.5 g, 15 mmol) in dry acetonitrile (5 mL) freshly distilled bromotrimethylsilane (8.9 mL, 67.5 mmol) was added dropwise at ambient temperature. A slightly exothermic reaction was observed, and the reaction mixture was stirred overnight. The next day the yellowish solution was concentrated in a vacuum to approximately three-quarters of starting volume and transferred to a distillation flask. The remaining volatiles (which kept the solution fluid to facilitate transportation) were completely removed and the silyl ester 2 was distilled as clear viscous uncolored liquid (6.4 g, 13.5 mmol, 90%), b.p. 116–117°C/0.05 mm. 1H-NMR (400 MHz, C6D6) δ = 0.29 (s, 36H, CH 3), 6.68 (dd, J HP = 35 Hz, J HP = 39 Hz, 2H, CH 2); 13C-NMR (100 MHz, C6D6) δ = 1.2 (s, CH3), 140.0 (t, JCP = 173 Hz, PCP), 142.8 (s, CH2); 31P-NMR (162 MHz, C6D6) δ = −3.1 (dd, J PH = 35Hz, J PH = 39 Hz), 29Si-NMR (C6D6) δ = 21.7 (m). Spectral data were in good agreement with those found in the literature5
- Experimental procedure for 2-(cyclopropylamino)ethane-1,1-diylbisphosphonic acid 3a: to a stirred solution of 2 (436 mg, 0.92 mmol) in dry dichloromethane (2 mL) cyclopropylamine (60 mg, 1.05 mmol) was added. The mixture was stirred for 2 h and the solvent was evaporated. Methanol (3–5 mL) was added and the mixture was stirred for another 0.5 h. Precipitate was collected on the filter and washed twice with methanol (3 mL) and then several times with ether (20 mL). Compound 3a (209 mg, 0.86 mmol) was obtained as a colorless crystalline solid in 93% yield. 1H-NMR (400 MHz, D2O) δ = 0.81–0.89 (m, 4H, CH 2cyclopropane), 2.52 (tt, JHP = 22 Hz, JHH = 7 Hz, 1H, PCHP); 2.74 (m, 1H, CH cyclopropane); 3.50 (td, JHP = 14 Hz, JHH = 7 Hz); 13C-NMR (100 MHz, D2O) δ = 3.3 (s, CH 2cyclopropane), 30.2, 36.4 (d, JCP = 122 Hz), 45.6; 31P-NMR (162 MHz, D2O) δ = 16.3