Diversity-oriented approach to spirooxindoles: application of a green reagent 'rongalite'

A range of functionalized spirooxindole derivatives have been assembled via the Diels-Alder (DA) reaction. Here, rongalite has been used to generate the key sultine building blocks which are useful latent diene equivalents in the DA chemistry. The di-bromo intermediates used here are produced by reacting the 1,2,4,5-tetrakis(bromomethyl)benzene with protected oxindole derivatives under operationally simple reaction conditions. In our study, we avoided the isolation of various intermediates, and thus reduced the cost and efforts related to the overall process. (C) 2015 Elsevier Ltd. All rights reserved.