Effect of the α-Alkyl Substituent of Conjugated Nitroolefins on the Formation of Cyclic Nitronic Esters vs. Nitrocyclopropanes in Their Reaction With Sulfur Ylides

Understanding the uniqueness of the stepwise [4 + 1] cycloaddition reaction between conjugated nitroalkenes and electrophilic carbene systems with a molecular electron density theory perspective

“…Several methods have been used for the synthesis of these heterocycles, such as asymmetric synthesis [ 6–8 ] (path a‐c), condensation of α‐nitroesters with aldehydes [ 9 ] (path d), o‐alkylation of nitroante anions with (α‐tosylvinyl)phosphonates [ 10 ] (path e), or stepwise condensation of a β‐bromo‐sulfonium salt and nitroethane [ 11 ] (path f) (Scheme 1). Although many synthetic methods have been developed, [ 12–15 ] practical protocols for the enantioselective construction of isoxazoline N‐oxides are very limited. The development of asymmetric synthesis of isoxazoline N‐oxides with high diastereoselectivity and enantioselectivity remains a challengeable task.…”

“…The development of asymmetric synthesis of isoxazoline N‐oxides with high diastereoselectivity and enantioselectivity remains a challengeable task. Although many synthetic methods have been developed, [ 12–15 ] practical protocols for the enantioselective construction of isoxazoline N‐oxides are very limited. The development of asymmetric synthesis of isoxazoline N‐oxides with high diastereoselectivity and enantioselectivity remains a challengeable task.…”

Synthesis of the reported structure of piperazirum using a nitro-Mannich reaction as the key stereochemical determining step

“…For the synthesis of β-nitroamine 8 we decided to make use of the reductive nitro-Mannich reaction as the starting nitroalkene 13 is readily available from a Henry reaction [50], imine 14 from the condensation of p -anisidine and isobutyraldehyde, and the process can easily be made asymmetric [45]. Conjugate addition of hydride to 13 and subsequent trapping of the nitronate anion with freshly prepared imine 14 in THF gave β-nitroamine 15 in 64% conversion and a dr of 70:30 (Scheme 4).…”

Asymmetric Michael Addition of Ketones to Nitroolefins Catalyzed by a New Chiral Catalyst

“…7b Initially, chiral thiourea organocatalysts 2 were examined in the Michael reaction of cyclohexanone 5a with trans-nitrostyrene 6a. As Table 1 shows, using 10 mol % 2 in the common solvents such as MeOH, THF, CH2Cl2, Toluene, EtOH, CH3CN and H2O led to the adduct 7a in low yields (entries [1][2][3][4][5][6][7][8] All reactions were carried out in toluene (1 mL) using 4 (0.14 mL, 5 eqiv.) and 5 (0.25 mmol, 1 equiv.)…”