propargylic ureas as powerful and versatile building blocks in the synthesis of various key medicinal heterocyclic compounds

this review article is an attempt to highlight the most important contributions toward the synthesis of various nitrogen-containing heterocyclic compounds from corresponding propargylic ureas through regio- and chemoselective 5-exo-dig and 6-endo-dig modes of n- and o-cyclization reactions. the review is divided into three major sections.

in the first section we only focus on 5-exo-dig n-cyclization fashion. in the second section 5-exo-dig o-cyclization is described. the third section is devoted to 6-endo-dig n- and o-cyclizations.