Compound 18
5-[(1E,3E)-5-Hydroxy-1,3-pentadienyl]-2,2-dimethylbenzo[1,3] dioxin-4-one
From: Total synthesis of marinomycin A using salicylate as a molecular switch to mediate dimerization
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InChIKey JZLFREDLVOXEGP-HJIKTHEYSA-N
Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.
2,2-Dimethyl-4-oxobenzo[1,3]dioxin-5-yl triflate (17, 2.62 g, 8.04 mmol) and (2E,4E)-5-(tributylstannyl)penta-2,4-dien-1-ol (16, 3.0 g, 8.04 mmol) in DMF (40 mL) were added to a suspension of lithium chloride (1.02 g, 24.1 mmol), Pd2(dba)3 (147 mg, 0.161 mmol) and triphenylarsine (0.394, 1.29 mmol) in DMF (10 mL) at room temperature. The resulting grey reaction mixture was heated at 80 °C for ca. 20 minutes and concentrated in vacuo at 45 °C. Purification by flash chromatography (silica gel, 20–40% ethyl acetate in hexane) afforded the dienol 18 (1.96 g, 94%) as a yellowish solid: mp = 74–75 °C; Rf = 0.15 (TLC, 1:3 ethyl acetate/hexane/EtOAc); 1H-NMR (500 MHz, CDCl3) δ 7.67 (d, J = 15.6 Hz, 1H), 7.43 (t, J = 8.0 Hz, 1H), 7.29 (d, J = 7.9 Hz, 1H), 6.83 (d, J = 8.1 Hz, 1H), 6.77 (dd, J = 15.6, 10.6 Hz, 1H), 6.53 (dd, J = 15.0, 11.0 Hz, 1H), 6.01 (dt, J = 15.2, 5.9 Hz, 1H), 4.26 (d, J = 5.7 Hz, 2H), 1.70 (s, 6H); 13C-NMR (125 MHz, CDCl3) δ 160.56 (e), 157.03 (e), 141.66 (e), 135.23 (o), 134.48 (o), 132.43 (o), 131.69 (o), 130.55 (o), 121.00 (o), 116.27 (o), 110.81 (e), 105.35 (e), 63.43 (e), 25.73 (o); IR (neat) 3407 (br, w), 2999 (w), 2863 (w), 1720 (s), 1611 (w), 1595 (m), 1573 (m), 1474 (m), 1389 (m), 1379 (m), 1317 (s), 1267 (s), 1204 (s), 1078 (m), 1044 (s), 1019 (m), 988 (s), 911 (s), 810 (m), 777 (m), 727 (s), 689 (s) cm−1; HRMS (ESI, [M+Na]+) calcd for C15H16O4Na 283.0946, found 283.0943.
