The Reacton of Isatin Azomethine Ylides with (Z)- and (E)-2-Oxoindolin-3-ylidene Acetophenones: Concerted vs Apparent Non-conceeted 1,3-Dipolar Cycloaddition

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 dipolarophiles in a 1,3-dipolar cycloaddition. The configurarion of the adducts was determined by 1 H-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