Synthesis of Ethyl 5‐Hydroxyisoxazolidine‐4‐carboxylates via Michael Addition/Intramolecular Hemiketalisation

Abstract

The 1,4-addition of N, O-bis(trimethylsilyl)hydroxylamine to alkylideneacetoacetates gave, in high yield, new 5-hydroxyisoxazolidine-4-carboxylates. The results of the accurate computational investigation on the mechanism at the DFT

Dynamics in Catalytic Asymmetric Diastereoconvergent (3 + 2) Cycloadditions with Isomerizable Nitrones and α-Keto Ester Enolates

“…Although it is difficult to discriminate between the conformers and diastereomers of the isoxazoline associated with nitrogen inversion in 1 H NMR analysis, , our findings clearly demonstrated that 6da and 7da are interconvertible. Such interconversion has also been reported in the similar 5-hydroxyisoxazolidines − prepared by the addition of the hydroxylamine to α,β-unsaturated carbonyl compounds . On the other hand, when we examined the reaction with isolable π-conjugated ( Z )-nitrones ( 1e – h ), which structurally resemble C -CN nitrones (Figures S6–S9), the corresponding (3 + 2) adducts were not detected (Table , entries 5–8).…”

Domino Michael–Michael and Aldol–Aldol Reactions: Diastereoselective Synthesis of Functionalized Cyclohexanone Derivatives Containing Quaternary Carbon Center

“…In order to study our proposed domino Michael–Michael reaction sequence, the precursor compounds α-arylmethylidene-β-keto esters ( 1a – h ) were synthesized following a reported procedure . Initially, for operational simplicity, another equivalent of the substrate itself was utilized as the electrophile.…”

Fast MacMillan’s Imidazolidinone-Catalyzed Enantioselective Synthesis of Polyfunctionalized 4-Isoxazoline Scaffolds

“…Solvents were commercially available and used after degasification. 1 H and 13 C NMR spectra were recorded using an Agilent-Technologies-Varian INOVA 400 MHz instrument with an 1 H/ 19 F/X 5-mm PFG ATB broadband probe, VT, single, double, and triple resonance, z-axis pulsed-field gradients, and a customized variable-temperature probe. Chemical shifts (δ) are reported in ppm relative to residual solvent signals General Procedure for the Synthesis of Nitrones 1l,m.…”

“…1 H NMR (400 MHz, CDCl 3 ) δ (ppm): 8.21−8.18 (m, 2H), 7.62 (s, 1H), 7.39−7.30 (m, 3H), 4.24 (t, J = 6.2 Hz, 2H), 3.60 (s, 3H), 2.99 (t, J = 6.2 Hz, 2H). 13 General Procedure for the Synthesis of 2,3-Dihydroisoxazoles 3a−q. The catalyst C or E was prepared by dissolving the commercial catalyst in minimal amount of dry Et 2 O, and an acidic solution of HCl in dry Et 2 O (1 M, 1.0 equiv) or TFA was added, respectively.…”

“…Our synthetic ligands contained 4isoxazolines as the core of the peptidomimetics, which are further decorated with suitable branches for binding therapeutics and diagnostics. 8 Successful synthesis of racemic 4-isoxazolines via 1,3-dipolar cycloaddition of nitrones with alkynes 9 and allenes, 10 cycloaddition of oxaziridines with alkynes, 11 cyclization of propargylic N-hydroxylamines, 12 conjugate addition of N-hydroxylamines to alkylidene acetoacetates, 13 and addition of organometallic reagents to isoxazolium salts 14 has been reported in the literature.…”