Iodine → Triphenylphosphine Oxide

Participants

Reaction Conditions

Reaction Steps

A suspension of 2′,3′,5′-tri-O-acetylinosine (1.58 g, 4.0 mmol), 2-propylimidazole (1.60 g, 14.4 mmol), Ph3P (2.58 g, 9.6 mmol), I2 (2.14 g, 8.32 mmol), and EtN(i-Pr)2 (3.6 mL, 2.67 g, 20.2 mmol) in dried toluene (40 mL) was stirred at 95° C. for 4 h. Volatiles were evaporated in vacuo, and the residue was extracted with boiling EtOAc. The combined extracts were evaporated to dryness, and the residue was chromatographed (CH2Cl2/MeOH, 1:40) to give a solid contaminated with Ph3PO. This material was dissolved in AcOH (160 mL), and AcCl (2.2 mL, 2.43 g, 31 mmol) was added. The solution was stirred at 65° C. overnight, and volatiles were evaporated in vacuo. The residue was dissolved in CH2Cl2 and extracted with 0.1 N NaOH/H2O. The aqueous layer was washed (CH2Cl2), and precipitation with CO2 followed by filtration and thorough washing (H2O) gave a solid (0.66 g, 72%). This material was dissolved in MeOH and decolorized with charcoal. Recrystallization (MeOH) gave 6-(2-propylimidazol-1-yl)purine as a colorless solid: mp 242.5-243.5° C.; UV (MeOH) max 278 nm (∈ 13 700), min 235 nm (∈ 5000); 1H NMR (300 MHz, DMSO-d6) δ 13.90 (br s, 1H), 8.86 (s, 1H), 8.69 (s, 1H), 8.36 (s, 1H), 7.07 (d, J=1.5 Hz, 1H), 3.18 (t, J=7.3 Hz, 2H), 1.72 (sext, J=7.3 Hz, 2H), 0.93 (t, J=7.3 Hz, 3H); 13C NMR (75 MHz, CDCl3) δ 155.5, 152.0, 149.8, 146.9, 145.8, 128.5, 123.6, 121.4, 32.2, 21.5, 14.5; HRMS m/z 228.1109 (M+[C11H12N6]=228.1123). Anal. Calcd for C11H12N6: C, 57.88; H, 5.30; N, 36.82. Found: C, 58.09; H, 5.19; N, 37.00.

Provenance & Evidence