Catalytic Enantioselective 1,3-Dipolar Cycloadditions of Nitrones with Propioloylpyrazoles and Acryloylpyrazoles Induced by Chiral π-Cation Catalysts
2010; American Chemical Society; Volume: 132; Issue: 44 Linguagem: Inglês
10.1021/ja1081603
ISSN1943-2984
AutoresAkira Sakakura, Masahiro Hori, Makoto Fushimi, Kazuaki Ishihara,
Tópico(s)Organic Chemistry Cycloaddition Reactions
ResumoA chiral copper(II) complex of 3-(2-naphthyl)-l-alanine amide successfully catalyzes the enantioselective 1,3-dipolar cycloaddition reaction of nitrones with propioloylpyrazole and acryloylpyrazole derivatives. The asymmetric environment created by intramolecular π-cation interaction gives the corresponding adducts in high yields with excellent enantioselectivity. This is the first successful method for the catalytic enantioselective 1,3-dipolar cycloaddition of nitrones with acetylene derivatives. The 1,3-dipolar cycloadducts can be stereoselectively converted to β-lactams via reductive cleavage of the N-O bond using SmI(2).
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