Reaction Steps
A mixture of 3 (424 g, 1.60 mol), trimethylorthoformate (0.37 L, 3.40 mol) and p-toluenesulfonic acid monohydrate (15 g, 79 mmol) in MeOH (1 L) was stirred for 5 h at room temperature. Triethylamine (11 mL, 79 mmol) was added, the resulting solution was concentrated in vacuo, diluted with EtOAc (2 L) and subsequently washed with H2O (2×1 L) and saturated aqueous NaCl (1×1 L). The organic layer was dried (MgSO4), filtered and concentrated in vacuo to yield an amber liquid (4, 481 g, 1.55 mol, 97%) with no need for further purification: 1H-NMR (400 MHz, CDCl3) δ=7.33 (d, J=8.7, 2H), 6.97 (d, J=8.7, 2H), 5.33 (s, 1H), 4.11 (q, J=7.1, 2H), 3.95 (t, J=6.4, 2H), 3.29 (s, 6H), 2.32 (t, J=7.4, 2H), 1.79 (m, 2H), 1.69 (m, 2H), 1.49 (m, 2H), 1.24 (t, J=7.1, 3H); 13C-NMR (400 MHz, CDCl3) δ=173.7, 159.3, 130.4, 128.0 (2C), 114.2 (2C), 103.2, 67.8, 60.4, 52.7 (2C), 34.4, 29.1, 25.8, 24.8, 14.4; IR(film) ν=2937, 1723, 1610, 1513, 1241, 1171, 1104, 1046, 980, 828 cm−1; HRMS (MALDI-FTMS) not detectable due to instability; detected: m/z 287.1254 (287.1252 calculated for parent aldehyde 3 C17H27O5Na, (M+Na)+).
