Compound 9b
(3aR,3bS,6aR,6bS,E)-2-benzyl-4-(4-methoxybenzylidene)tetrahydrocyclopenta[3,4]cyclobuta[1,2-c]pyrrole-1,3,5(2H,3aH,6bH)-trione
From: Switchable regioselectivity in amine-catalysed asymmetric cycloadditions
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Compound data: CIF
Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.
The title compound was prepared according to the general procedure for asymmetric β,γ-regioselective [2 + 2] cycloaddition reaction as outlined in the synthesis of 9a. 9b, white solid, 25.1 mg, 65% yield; [α]D20 = -54.3 (c = 0.78 in CHCl3); 99% e.e., determined by HPLC analysis [Daicel chiralpak AD, n-hexane/i-PrOH = 60/40, 1.0 mL/min, λ = 254 nm, t (major) = 16.93 min, t (minor) = 19.25 min]; 1H NMR (400 MHz, CDCl3): δ (ppm) 7.70 (d, J = 8.8 Hz, 2H), 7.54 (d, J = 1.6 Hz, 1H), 7.45-7.43 (m, 2H), 7.36-7.30 (m, 3H), 7.05 (d, J = 8.8 Hz, 2H), 4.79 (s, 2H), 3.92 (m, 1H), 3.87 (s, 3H), 3.20 (m, 1H), 3.12 (dd, J = 6.4 Hz, 2.4 Hz, 1H), 3.05 (dd, J = 6.4 Hz, 4.4 Hz, 1H), 2.78 (dd, J = 20.0 Hz, 8.8 Hz, 1H), 2.66 (dd, J = 20.0 Hz, 2.0 Hz, 1H); 13C NMR (100 MHz, CDCl3): δ (ppm) 205.5, 177.5, 177.4, 161.8, 137.3, 135.6, 133.7, 132.3, 128.8, 128.6, 128.1, 126.3, 114.7, 55.5, 44.4, 44.1, 42.8, 42.0, 35.6; ESI-HRMS: calcd. for C24H21NO4+Na+ 410.1363, found 410.1372.