Reaction Steps
A 2-necked round bottom flask with 5-iodouridine (100 mg, 270 μmol), 5-formyl-2-thiopheneboronic acid (1.5 eq) and Cs2CO3 (2 eq.) was purged with N2. Upon addition of TPPTS (0.0625 eq.), Na2Cl4Pd (0.025 eq.) and degassed H2O (5 mL) the mixture turned orange in colour. The reaction was stirred under N2 for 1 h at 60° C., turning brown/black. Once the starting material was fully consumed, the reaction mixture was cooled to room temperature. The pH was adjusted to 7 with HCl 1% and the reaction mixture was filtered through Celite. The solvents were removed to give a colourless powder. After purification, the title compound was obtained in 23% yield (16 mg). δH (400 MHz, DMSO-d6) 3.65-3.85 (2H, m, H-5′), 3.90-3.95 (1H, m, H-4′), 4.02-4.17 (2H, m, H-2′ and H-3′), 5.11 (1H, d, J=5.9 Hz, OH-3′), 5.54 (1H, d, J=5.0 Hz, OH-2′), 5.60 (1H, t, J=4.3 Hz, OH-5′), 5.80 (1H, d, J=3.0 Hz, H-1′), 7.56 (1H, d, J=4.1 Hz, Th), 7.93 (1H, d, J=4.0 Hz, Th), 9.02 (1H, s, H-6), 9.87 (1H, s, CHO), 11.9 (1H, s, NH); δC (75.5 MHz, DMSO-d6) 59.6 (C-5′), 68.7 (C-3′), 74.5 (C-2′), 84.4 (C-4′), 89.5 (C-1′), 106.9 (C-5), 122.9, 137.3, 138.7, 141.6, 144.4, 149.4 (C-2+C-6+C—Th), 161.4 (C-4), 184.3 (CHO). m/z (ESI) 353.0448 [M−H]−, C14H13O7N2S requires 353.0449.
