Compound 11
Ethyl (5S,5aS,5bS,5cR,9aS,10R,10aR,11R)-7-((E)-4-bromobenzylidene)-10-cyano-1,3,8-trioxo-2-phenyl-2,3,5,5a,5b,5c,6,7,8,9,9a,10-dodecahydro-1H,11H-5,11-ethenoindeno[2',1':1,3]cyclopropa[1,2-d][1,2,4]triazolo[1,2-a]pyridazine-10-carboxylate
From: Organocatalytic stereoselective [8+2] and [6+4] cycloadditions
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Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.
Compound 9d (92.9 mg, 0.20 mmol) was dissolved in CDCl3 (2 mL) and transferred to a vial containing a magnetic stirring bar. 4-Phenyl-3H-1,2,4-triazole-3,5(4H)-dione (42 mg, 0.24 mmol) was added and reaction mixture stirred for 3 h at rt. The product 11 was obtained as a colorless oil after FC on silica gel (gradient pentane:EtOAc 8:2 to 6:4) in 48% yield. 1H NMR (400 MHz, CDCl3) δ7.58 – 7.54 (m, 1H), 7.54 (d, J = 8.5 Hz, 2H), 7.48 – 7.41 (m, 5H), 7.21 (d, J = 8.4 Hz, 2H), 6.39 (ddd, J = 7.9, 6.1, 1.7 Hz, 1H), 6.12 (t, J = 6.8 Hz, 1H), 5.36 (ddd, J = 6.1, 4.7, 1.7 Hz, 1H), 5.12 (dd, J = 6.1, 1.3 Hz, 1H), 4.51 – 4.31 (m, 2H), 3.26 (dd, J = 14.9, 6.0 Hz, 1H), 3.04 – 2.90 (m, 2H), 2.86 (dd, J = 14.7, 4.8 Hz, 1H), 2.73 (t, J = 14.5 Hz, 1H), 2.47 (ddd, J = 14.9, 11.0, 2.4 Hz, 1H), 1.98 (t, J = 3.8, 1H), 1.76 (dd, J = 5.3, 3.2 Hz, 1H), 1.44 (t, J = 7.1 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ 197.4, 168.2, 156.9, 156.8, 135.7, 133.8, 133.4, 132.1 (2C), 131.3 (2C), 131.2, 129.3 (2C), 129.1, 128.6, 125.7 (2C), 125.3, 123.6, 115.5, 64.3, 54.9, 53.5, 53.0, 45.3, 42.4, 38.0, 37.1, 35.2, 27.7, 17.7, 14.2. HRMS calc. for C33H27BrN4O5 661.1057 [M+Na]+, found 661.1060. UPC2 IB, CO2/iPrOH, gradient 99:1 to 60:40, 3 mL·min-1, 40 °C, 120 bar; tmajor = 5.69 min; tminor = 6.00 min (99% ee). Crystal data for 11: C33H26BrN4O5, M = 638.49, orthorhombic, space group P 212121 (no. 115), a = 7.2175(3) Å, b = 14.7298(8) Å, c = 28.2016(10) Å, Flack parameter = -0.019, V = 2998.2(2) Å3, T = 273 K, Z = 4, dc = 1.415 g cm-3, μ(Mo Kα, λ = 0.71073 Å) = 1.419 mm-1, 24473 reflections collected, 6130 unique [Rint = 0.0966], which were used in all calculations. Refinement on F2, final R(F) = 0.1661, Rw(F2) = 0.1715. CCDC number 1469731. The crystals were obtained after recrystallization from MeOH.
