Dimethylbarbituric acid → Ethyl tert-butoxy[4-(2-hydroxy-4-methylphenyl)-2-methyl-5,6,7,8-tetrahydro[1]benzothieno[2,3-b]pyridin-3-yl]acetate

Participants

Reaction Steps

To a stirred solution of ethyl {4-[2-(allyloxy)-4-methylphenyl]-2-methyl-5,6,7,8-tetrahydro[1]benzothieno[2,3-b]pyridin-3-yl}(tert-butoxy)acetate (Step 8, 370 mg, 729 μmol) in dichloromethane (10 mL) was added 1,3-dimethylbarbituric acid (569 mg, 3.64 mmol), and the reaction was evacuated and filled with nitrogen. Palladium tetrakis(triphenylphosphine) (17 mg, 15 μmol) was added and the reaction was heated to reflux for 16 hours. Further palladium tetrakis(triphenylphosphine) (17 mg, 15 μmol) was added and the reaction was heated to reflux for a further 4 hours. The reaction was concentrated in vacuo and preabsorbed onto silica. The residue was purified using ISCO Companion with a Redisep silica gel 12 g cartridge and a gradient of heptane and ethyl acetate (0% to 20%). Product containing fractions were concentrated in vacuo to give the title compound as a pair of diastereoisomers as a colourless oil, 214 mg, in a 63% yield. The other pair of minor diastereoisomers co-eluted with unreacted starting material and were not isolated. LC-MS (12 min acidic) 6.89 mins 100% pure by UV, ES+/APCI+ 468, ES−/APCI− 466 1H NMR (400 MHz, CDCl3) δ ppm 1.01 (s, 9H) 1.20 (t, 3H) 1.62-1.85 (m, 4H) 2.02-2.14 (m, 2H) 2.41 (s, 3H) 2.74 (s, 3H) 2.78-2.85 (m, 2H) 4.08-4.18 (m, 2H) 5.14 (s, 1H) 6.78 (s, 1H) 6.82 (d, 1H) 7.17 (d, 1H).

Provenance & Evidence