Highly enantioselective 1,3-dipolar cycloaddition reactions of 2-benzopyrylium-4-olate catalyzed by chiral Lewis acids.
We have found that significant levels of enantioselectivity are obtained in the 1,3-dipolar cycloadditions of 2-benzopyrylium-4-olate using chiral 2,6-bis(oxazolinyl)pyridine (Pybox)-rare earth metal triflate complexes as chiral Lewis acid catalysts. The reactions with benzyloxyacetaldehyde derivatives catalyzed by Sc(III)-Pybox-i-Pr (10 mol %) proceeded to give endo-adducts selectively with high enantioselectivity (up to 93% ee). The reaction with benzyl pyruvate under similar conditions gave an exo-adduct selectively with 87% ee. In the reaction with 3-acryloyl-2-oxazolidinone, Yb(III)-Pybox-Ph was found to be effective in providing an exo-adduct with extremely high enantioselectivity (98% ee).
Suga
Hiroyuki
H
Department of Chemistry and Material Engineering, Faculty of Engineering, Shinshu University, Wakasato, Nagano 380-8553, Japan. sugahio@gipwc.shinshu-u.ac.jp
Inoue
Kei
K
Inoue
Shuichi
S
Kakehi
Akikazu
A
D000447:Aldehydes / Q000737:chemistry; D008698:Mesylates / Q000737:chemistry; D008674:Metals, Rare Earth; D010080:Oxazoles / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D011773:Pyruvates / Q000737:chemistry; D012538:Scandium / Q000737:chemistry; D013237:Stereoisomerism; D015019:Yttrium / Q000737:chemistry
D000447:Aldehydes; D008698:Mesylates; D008674:Metals, Rare Earth; D010080:Oxazoles; D011725:Pyridines; D011773:Pyruvates; C436603:scandium triflate; D015019:Yttrium; D012538:Scandium