The Effect of High Pressure on the Diastereoselectivity of Intermolecular All-Carbon Diels-Alder Reactions

Abstract

The influence of high pressure on the diastereoselectivity of the intermolecular all-carbon Diels ± Alder reaction of the phenylbutadienes 1 a ± c with the dicyanoethylenes 2 a ± d to give the cyclohexenes 3 ± 8 is described. The differences in activation volume, DDV = , for the two pathways leading to cis and trans diastereomers range from À (0.7 AE 0.8) to À (6.4 AE 0.6) cm 3 mol À1, indicating a pressure-induced increase of diastereoselectivity in favour of the cis adducts 3 a ± d, 5 a ± d and 7 b ± d.

Solvation effects drive the selectivity in Diels–Alder reaction under hyperbaric conditions

“…Generally, the more compact endo approach is favored by a HPs. 2,19,20 In some cases endo kinetic adducts are obtained under hyperbaric cycloaddition, while exo thermodynamic ones are generated by heating. 21 The activation observed in organic reactions in liquid phase is explained by the Evans-Polanyi equation, which connects a negative activation volume with the acceleration of the reaction with pressure increase.…”

Nazarov cyclization of divinyl ketones bearing an ester group at the β-position: a remarkable effect of α-substitution and alkene geometry on regioselectivity

“…Step-1: 14 Yield: 86%; colorless oil; R f = 0.3 (10% EtOAc/hexanes); 1 H NMR (300 MHz, 1H), 6.50 (d,J = 15.8 Hz,1H), 6.15 (dd,J = 6.7,15.8 Hz,1H),4.12 (q,J = 6.7 Hz,1H), 2.88 (br s, 1H), 1.68-1.53 (m, 2H), 0.92 (t, J = 7.4 Hz, 3H); 13 C NMR (75 MHz, CDCl 3 ): δ 136. 6,132.1,130.0,128.3,127.3,126.2,74.0,29.9,9.5;IR (neat):  max 3393,3025,2967,1609,1495,963,747,690 Step-2: 15 Yield: 85%; colorless oil; R f = 0.5 (10% EtOAc/hexanes); 1 H NMR (500 MHz, 199.9,141.4,129.7,128.3,127.6,125.4,33.3,7.5;IR (neat):  max 2977, 1663,1611,1494,1352,1187,1119,978,745,690…”

“…Step-2: Yield: 76%; colorless oil; R f = 0.5 (10% EtOAc/hexanes); 1 H NMR (300 MHz, 7, 158.0, 149.9, 134.3, 130.0, 129.1, 127.3, 113.6, 54.9, 54.8, 16 42.9,28.1,21.7,11.2;IR (neat):  max 2959,1663,1510,1459,1242,1177,1036,824,670 cm -1 ; HRMS (ESI): calcd for C 15 Step-2: Yield: 82%; colorless oil; R f = 0.5 (10% EtOAc/hexanes); 1 H NMR (300 MHz, 7,149.6,134.3,131.9,117.5,42.1,28.1,21.7,11.0;IR (neat) 6,159.6,137.9,135.0,131.3,128.3,113.7,55.1,30.4,13.0,8.8;IR (neat): 2934,1661,1602,1509,1252,1176,1031,829 7,148.4,134.4,30.1,28.0,21.8,11.1,8.7;IR (neat)…”

Highly Enantioselective Conjugate Additions to α,β‐Unsaturated Ketones Catalyzed by a (Salen)Al Complex.

“…FTIR (cm -1 ): 2961 (s), 2874 (m), 1676 (s), 1632 (m), 1464 (w), 1188 *w), 1045 (w), 980 (m). 1 H NMR (500 MHz, CDCl 3 ): δ 6.81 (1H, dt, J = 16.0, 7.0 Hz, HC=CHCO), 6.08 (1H, d, J = 16.0 Hz, HC=CHCO), 2.52 (2H, t, J = 7.5 Hz, COCH 2 ), 2.18 (2H, dd, J = 14.5, 7.0 Hz, CH 2 CH=C), 1.58 (tt, J = 7.5, 7.5 Hz, COCH 2 CH 2 ), 1.49 (tq, J = 7.0, 7.0 Hz, HC=CHCH 2 CH 2 CH 3 ), 1.32 (tq, J = 7.5, 7.5 Hz, CH 2 CH 2 CH 2 CH 3 ), 0.93 (3H, t, J = 7.0 Hz, COCH 2 CH 2 CH 3 ), 0.90 (3H, t, J = 7.0 Hz, CH 2 CH 2 CH 3 ). 13 Diethyl (2-oxopropyl)phosphonate (4.04 mL, 20.1 mmol, 1.05 equiv.…”

“…Product: FTIR (cm -1 ): 2967 (m), 2874 (w), 2247 (w), 1676 (s), 1626 (m), 1362 (m), 1258 (m), 988 (m). 1 H NMR (500 MHz, CDCl 3 ): δ 6.65 (1H, dt, J = 16.5 Hz, HC=CHCO), 6.02 (1H, d, J = 16.5 Hz, HC=CHCO), 2.27 (3H, s, COCH 3 ), 2.23 (2H, d, J = 8.0 Hz, CH 2 CN), 1.18 (2H, d, J = 8.0 Hz, CH 2 C(CH 3 ) 2 ), 1.12 (6H, s, C(CH 3 ) 2 ). 13 C NMR (100 MHz, CDCl 3 ): δ 198.6, 153.9, 129.0, 119.9, 37.6, 36.8, 27.7, 26.2, 13.2.…”