Synthesis of cyclic polycationic allenes from a low coordinate carbocation

Abstract

The preparation and reactivity of a 1,3-<em>bis</em>(dimethylamino)iodopropargyl salt (<strong>3‧2I</strong>) will be discussed. Prepared <em>via</em> a multistep pathway, the cations possess three potentially reactive functional groups, namely: (<strong>1</strong>) an alkyne, (<strong>2</strong>) a carbocation, and (<strong>3</strong>) an alkyl halide. This density of potential reactive sites provides a unique starting point for preparing heterocyclic compounds. The reactions of <strong>3‧2I</strong> with organophosphorus compounds have been found to generate a variety of cyclic allenes, including the smallest in an eight-membered dicationic <strong>C₃-P₂C₃‧2BPh₄</strong> to the largest in a twenty-two-membered tetracation <strong>[C₆-P₂C₃]‧2I‧2BPh₄</strong>.The incorporation of the allenic dication into a metallocene and into a chiral complex was also achieved. The newly isolated compounds have all been characterized using NMR and IR spectroscopy, LRMS, HRMS, and Xray crystallography.