Kazushige Hori

Palladium-catalyzed asymmetric 1,3-dipolar cycloaddition of nitrones to olefins

Asymmetric 1,3-dipolar cycloaddition of nitrone 2 to olefin 1 was catalyzed by chiral phosphine - palladium complexes to give isoxazolidine 3 in high yield with high enantioselectivity up to 91% ee.

Lanthanide-catalyzed asymmetric 1,3-dipolar cycloaddition of nitrones to alkenes using 3,3′-bis(2-oxazolyl)-1,1′-bi-2-naphthol (BINOL-Box) ligands

Abstract New BINOL-derived ligands, 3,3′-bis(2-oxazolyl)-1,1′-bi-2-naphthols (BINOL-Box), bearing chiral bis-oxazoline at the 3,3′-carbons, were synthesized from commercially available 1,1′-bi-2-naphthol (BINOL). With the new ligands obtained, we found that asymmetric 1,3-dipolar cycloaddition reaction of N -benzylidenebenzylamine N -oxide ( 2 ) to 3-(( E )-2-butenoyl)-1,3-oxazolidin-2-one ( 1 ) was catalyzed by BINOL-Box–scandium complexes to give isoxazolidine 3 in high yield with high diastereo- and enantioselectivity. For example, the reaction of 1 with 2 catalyzed by a 6 mol% ( S , R )- 7d and 5 mol% Sc(OTf) 3 complex proceeded to give the endo -3 as the major diastereomer with an endo : exo ratio of 97:3 and 87% ee of the endo -product in the presence of 4 A molecular sieves. Interestingly, the absolute configuration of the major product was changed according to the kind of additive used.

Palladium(II)-catalyzed 1,3-dipolar cycloaddition of nitrones with enol ethers

Abstract The 1,3-dipolar cycloadditions of enol ethers as electron-rich olefins with C -phenyl- N -alkyl nitrones proceeded smoothly in the presence of easy handling palladium(II) catalysts under mild conditions to give isoxazolidines in good yield.