Charge‐activated TADDOLs: Recyclable organocatalysts for asymmetric (hetero‐)Diels–Alder reactions

Abstract

Several charge-containing TADDOL salts were synthesized and used as organocatalysts in asymmetric Diels-Alder and hetero-Diels-Alder reactions.Their catalytic activity was found to exceed that of a noncharged analog while maintaining or improving upon the enantioselectivity. The enhanced activities of the TADDOL salts enabled them to act as presumed hydrogen bond donor catalysts in the Diels-Alder and hetero-Diels-Alder reactions of 1,3-cyclohexadiene with methyl vinyl ketone at 40 C and 2-phenoxy-1,3-butadiene with ethyl glyoxylate at room temperature, respectively. Given the ionic nature of these charge-activated catalysts, it also proved possible to recycle and reuse the TADDOL without chromatography or the need for a recrystallization.

Electrostatically Enhanced 3- and 4-Pyridyl Borate Salt Nucleophiles and Bases

“…29 1 H NMR (500 MHz, CD 3 OD) δ 8.58 (s, 1H), 8.28 (dd, J = 5.0, 1.9 Hz, 1H), 7.92 (dt, J = 7.5, 1.8 Hz, 1H), 7.24 (dd, J = 7.5, 5.0 Hz, 1H). 11 B NMR (128 MHz, CD 3 OD) δ 3.32 (d, J = 51.8 Hz). 13 C{H} NMR (126 MHz, CD 3 OD) [missing one resonance] δ 152.4, 146.9, 141.8, 124.3.…”

“…58 1 H NMR (500 MHz, acetone-d 6 ) δ 8.26 (d, J = 5.5 Hz, 2H), 7.35 (d, J = 4.6 Hz, 2H). 11 B NMR (161 MHz, CD 3 OD) δ 2.75 (d, J B-F = 42.9 Hz). 13 C{H} NMR (126 MHz, CD 3 OD) [missing 1 resonance] δ 147.5, 128.7.…”

“…s, 1H), 7.58 (ddd, J = 13.1, 8.4, 1.3 Hz, 8H), 7.26 (dt, J = 5.6, 2.9 Hz, 6H), 7.06 (d, J = 8.0 Hz, 7H), 6.87 (dd, J = 7.5, 4.7 Hz, 1 Hz), 1.25 (s, 27H). 11 B NMR (161 MHz, CD 2 Cl 2 ) δ −7.86. 13 C{H} NMR (126 MHz, CD 2 Cl 2 ) δ 159.7 (q, J B-C = 48.9 Hz), 155.…”

“…1 H NMR (500 MHz, CD 2 Cl 2 ) δ 8.51 (s, 1H), 8.04 (dd, J = 4.9, 1.9 Hz, 1H), 7.84 (d, J = 7.3 Hz, 1H), 7.36−7.19 (m, 14H), 7.09 (d, J = 8.2 Hz, 6H), 7.01 (dd, J = 7.5, 4.9 Hz, 1H), 6.77 (dd, J = 9.1, 2.6 Hz, 8H), 3.05 (s, 24H), 1.27 (s, 27). 11 B NMR (161 MHz, CD 2 Cl 2 ) δ −7.86. 13 C{H} NMR (126 MHz, CD 2 Cl 2 ) [missing 1 resonance] δ 159.9 (q, J B-C = 53.1 Hz), 155.9, 154.1, 144.…”

“…1 H NMR (500 MHz, CDCl 3 ) δ 8.71 (s, 1H), 8.34 (d, J = 4.9 Hz, 1H), 7.84 (d, J = 7.6 Hz, 1H), 7.09 (t, J = 6.2 Hz, 1H), 3.02 (t, J = 7.4 Hz, 8H), 1.47 (quintet, J = 7.6 Hz, 8H), 1.31 (sextet, J = 7.4 Hz, 8H), 0.93 (t, J = 7.4 Hz, 12H). 11 B NMR (161 MHz, CDCl 3 ) δ 3.24. 13 ).…”