Abstract

The proximity of the 4,5-diamino groups in a 9,9'-dimethylxanthene skeleton provides unique reactivity due to aggregation effects. While treatment with 1 equiv of an isocyanate yields the diurea and starting material, under similar conditions, Boc(2)O provides essentially only the monocarbamoyl derivative. (C) 2007 Elsevier Ltd. All rights reserved.