Catalytic enantioselective epoxidation of nitroalkenes

Abstract

Nitroepoxides are potentially exploitable as synthons with vicinal electrophilic centers. Nevertheless, although advances have been made in the field, enantioselective epoxidation of nitroalkenes is still a challenging process. Herein we show a convenient procedure for the preparation of optically active nitroepoxides in high enantiomeric excess and high chemical yield. The kinetic data of the best catalyst have been examined using computational methods based on DFT calculations. Interestingly, the results demonstrate that the enantioselectivity of the epoxidation of nitroalkenes by this kind of catalyst is not only kinetically but also thermodynamically controlled.

Sequential Formal [4+1]‐Cycloaddition, C−H Functionalization and Suzuki–Miyaura Cross‐Coupling for the Synthesis of Trisubstituted Isoxazolines

“…Second fraction (90–100 °C, 0.6 torr) contained target olefin 4 f (19.4 g, 80 % yield). Spectra were in agreement with literature data [29] …”

Regioselective Opening of Nitroepoxides with Unsymmetrical Diamines

“…Product was obtained as a pale yellow crystal (yield 2.9 g, 91%), mp 82–84 °C; 1 H NMR (300 MHz, chloroform- d ) δ 8.05 (s, 1H), 7.51–7.40 (m, 2H), 7.44–7.33 (m, 2H), 2.46 (d, J = 1.2 Hz, 3H); 13 C NMR (75 MHz, chloroform- d ) δ 148.0, 136.0, 132.2, 131.1, 130.8, 129.2, 14.0; LRMS (EI) mass calcd for C 9 H 8 ClNO 2 [M + ] 197.0; found 197.0; FT-IR δ 3091, 2988, 1508, 1304 cm –1 …”

“…The obtained product was a pale yellow oil (yield 1.8 g, 84%): 1 H NMR (500 MHz, CDCl 3 ) δ 7.41 (m, 3H), 7.30 (m, 2H), 4.56 (s, 1H), 1.78 (s, 3H); 13 C NMR (126 MHz, CDCl 3 ) δ 131.0, 129.3, 128.7, 126.3, 88.8, 62.6, 12.2 ppm; HRMS (EI) calcd for C 9 H 9 NO 3 (M) 179.0582, found 179.0587; IR (KBr) δ 3062, 3028, 2948, 1555, 1495, 1354, 1158, 899 cm –1 …”

Catalyst-Free Synthesis of Benzofuran Derivatives from Cascade Reactions between Nitroepoxides and Salicylaldehydes

“…The synthesis and chemistry of α-nitroepoxides were first developed by Newman and Angier in 1970 . They could be easily prepared by the oxidation of β-nitrostyrenes using different reagents . However, until the 21st century, the development of their chemistry and reactions was limited to a few reports including their photochemical reactions .…”

“…1 They could be easily prepared by the oxidation of β-nitrostyrenes using different reagents. 2 However, until the 21st century, the development of their chemistry and reactions was limited to a few reports including their photochemical reactions. 3 During the first three decades, the most essential aspects of these structures were their reactions in some carbohydrate derivatives.…”