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Paper | Special issue | Vol 37, No. 3, 1994, pp.1673-1686
Published online, 1st January, 1970
DOI: 10.3987/COM-93-S136
The Reaction of Isatin Azomethine Ylides with (Z)- and (E)-2-Oxoindolin-3-ylidene Acetophenones: Concerted vs Apparent Non-conceeted 1,3-Dipolar Cycloaddition

Adele Casaschi, Giovanni Desimoni*, Giuseppe Faita, Anna Gamba Invernizzi, and Paolo Grünanger*

*Dipartamento di Chimica Organica, Università de Pavia, V. le Taramelli 10, 27100 Pavia, Italy

Abstract

The reaction of 1-benzyl-5-bromoisatin with proline, sarcosine, or glycine gives azomethine ylides that can be trapped by (Z)- or (E)-2-oxoindolin-3-ylidene acetophenones acting as dipolmphiles in a 1,3-dipolar cycloaddition. The configuration of the adducts was determined by 1H-nmr with nOe experiments. The kinetically controlled adducts always retain the configuration of the reacting dipolarophile but they can rearrange, sometimes under extremely mild conditions. The rearrangements were demonstrated to involve a 1,3-dipolar cycloreversion/ cycloaddition sequence since the intermediates were trapped by more reactive dipolarophiles.