Collect. Czech. Chem. Commun. 2009, 74, 835-856
Published online 2009-04-28 09:36:48

1,3-Dipolar cycloadditions of 5-(4-methoxyphenyl)- and 5-(1H-indol-3-yl)-substituted (1Z,4R*,5R*)-1-(arylmethylidene)-4-benzamido-3-oxopyrazolidin-1-ium-2-ides to olefinic dipolarophiles

Lidija Pezdirc, Branko Stanovnik and Jurij Svete*

Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, P.O. Box 537, 1000 Ljubljana, Slovenia


1,3-Dipolar cycloadditions of (1Z,4R*,5R*)-1-(arylmethylidene)-4-benzamido-5-(4-methoxyphenyl)-3-oxopyrazolidin-1-ium-2-ides 6a6f and their 5-(1H-indol-3-yl) analogues 6g6j to olefinic dipolarophiles 79 were studied. Stereochemistry was controlled by the structure of dipoles 6 and dipolarophiles 79. Reactions of ortho-unsubstituted dipoles 6a6c, 6g gave the major isomers 10 and 14 with syn-oriented protons H-3 and H-5, whilst ortho-disubstituted dipoles 6d, 6e, 6j gave cycloadducts 11 and 12 with anti-oriented protons H-3 and H-5. In comparison with their 5-phenyl-substituted analogues, dipoles 6a6e, 6g, 6j were less reactive in cycloadditions to olefinic dipolarophiles 79. This was reflected in longer reaction times, lower yields, and sometimes in lower selectivity as well. The relative configurations of cycloadducts were determined by NMR.

Keywords: Azomethine imides; 1,3-Dipolar cycloadditions; Cyclisations; Pyrazolidinones; Synthetic methods; NMR spectroscopy.

References: 48 live references.