Palladium and rhodium-catalyzed intramolecular [2+2+2] cycloisomerizations in molten tetrabutylammonium bromide

The cycloisomerization reaction of triacetylenic macrocycles 1 was carried out in molten n-BU4NBr using either the Wilkinson's catalyst RhCl(PPh3)(3), or PdCl2 leading to good yields of the corresponding cycloisomerized compounds. It was possible to recycle the catalytic system. When PdCl2/TBAB was used, palladium natioparticles were identified by means of transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). (c) 2007 Elsevier Ltd. All rights reserved.