Electronic effects in 1,3-dipolar cycloaddition reactions of N-alkyl and N-benzyl nitrones with dipolarophiles
作者:Andrei Bădoiu、E. Peter Kündig
DOI:10.1039/c1ob06144e
日期:——
1,3-Dipolar cycloadditions afforded fast access to isoxazolidines bearing N-alkyl or N-benzyl substituents. The electronic properties of the substituents in the nitrones define the activity of the dipoles and modulate diastereoselectivity in the non-catalyzed reactions. Using a chiral one-point binding ruthenium Lewis acid catalyst, products were obtained in good yields and with excellent regio-, diastereo-
Lipase-catalyzed asymmetric synthesis of oxathiazinanones through dynamic covalent kinetic resolution
作者:Lei Hu、Yan Zhang、Olof Ramström
DOI:10.1039/c4ob00365a
日期:——
A domino addition–lactonization pathway has been applied to a dynamic covalent resolution protocol, leading to efficient oxathiazinanone formation as well as chiral discrimination. A new, double biocatalytic pathway has furthermore been proposed and evaluated where the initial product inhibition could be efficiently circumvented.
Asymmetric “Acetylenic” [3+2] Cycloaddition of Nitrones Catalyzed by Cationic Chiral Pd<sup>II</sup>
Lewis Acid
作者:Kazuya Honda、Koichi Mikami
DOI:10.1002/asia.201801016
日期:2018.10.4
Highly enantioselective [3+2] cycloaddition of ynones and nitrones has been developed. Very bulky ligand, DTBM‐SEGPHOS, was used for an effective asymmetric induction over distal reaction centers on the linear ynone dipolarophile and for prevention of PdII catalyst deactivation by coordination of the nitrones. The reaction has wide scope of substrates in both ynones and nitrones.
Lewis Acid Catalyzed Annulation of Nitrones with Oxiranes, Aziridines, and Thiiranes
作者:Stalin R. Pathipati、Vipender Singh、Lars Eriksson、Nicklas Selander
DOI:10.1021/acs.orglett.5b02195
日期:2015.9.18
Lewis acid catalyzed annulation of three-membered heterocycles with nitrones has been developed. Oxiranes, aziridines, and thiiranes were used as substrates for the synthesis of various six-membered heterocycles using Al or In catalysts. This catalytic protocol demonstrates a broad substrate scope and provides access to new structural motifs in high yields and in excellent selectivity under mild reaction