Reaction Steps
To a flamed-dried round-bottomed flask was added (E)-methyl 11-((tetrahydro-2H -pyran-2-yl)oxy)-3-(tributylstannyl)undec-2-enoate (1 equiv, 25.5 mmol, 15.0 g), DMF (30 mL), and CuCl (3 equiv, 76.5 mmol, 7.57 g). The reaction was stirred for 3 h at rt, quenched with aq. NH4Cl/NH4OH (pH ˜8) (35 mL), and stirred for 2 h open to the air. The solution was diluted with H2O (50 mL) and Et2O (50 mL). The layers are separated and the aqueous layer was extracted with Et2O (2×50 mL). The combined organic layers were washed with brine (75 mL), dried with MgSO4, concentrated in vacuo, and purified by flash chromatography (step gradient, 10% EtOAc/Hex to 15% EtOAc/Hex) to afford (2E,4E)-dimethyl 3,4-bis(8-((tetrahydro-2H-pyran-2-yl)oxy)octyl)hexa-2,4-dienedioate (6.27 g, 10.5 mmol, 83%). TLC Rf=0.19 (10% EtOAc/Hex); 1HNMR (500 MHz): δ 5.84 (bs, 2H), 4.55-4.61 (2H), 3.83-3.92 (2H), 3.69-3.77 (s plus ovlp. m, 8H), 3.47-3.55 (m, 2H), 3.38 (dt, 2H, J1=9.6 Hz, J2=6.7 Hz), 2.72-2.84 (4H), 1.78-1.89 (2H), 1.69-1.76 (2H), 1.50-1.63 (12H), 1.28-1.41 (20H); 13CNMR (125 MHz): δ 166.5, 161.8, 117.6, 98.8, 67.7, 62.3, 51.2, 30.8, 29.7, 29.6, 29.4, 29.3, 29.1, 28.7, 26.2, 25.5, 19.7; FTIR: 2927, 2855, 1718, 1628, 1433, 1351, 1193, 1163, 1136, 1078, 1023, 986, 905, 868, 814 cm−1; HRMS-ESI: calc. for C34H58NaO8 (M+Na)+: 617.4029. found: 617.4039.
