A novel sequential palladium/ruthenium-catalysed four component process is described involving carbonylation of an aryl/heteroaryl iodide followed by allenylation to generate (pi-allyl) palladium species which are intercepted by nitrogen nucleophiles to afford 1,6-dienes. Subsequent Ring-Closing Metathesis (RCM) affords C-acyl-N-heterocycles in good yield. These heterocycles proved to be active dipolarophiles in sequential and cascade 1,3-dipolar cycloaddition reactions (1,3-DC) as exemplified by reactions with nitrones and azomethine ylides. (C) 2003 Elsevier Science Ltd. All rights reserved.
Synthesis of Δ3-pyrrolines and Δ3-tetrahydropyridines via microwave-accelerated ring-closing metathesis
Microwave irradiation effects ring-closing metathesis of electron-deficient and sterically conjested double bonds with a drastic reduction in reaction time and reduced catalyst loading. (C) 2003 Elsevier Science Ltd. All rights reserved.