Versatile Pyrolytic Synthesis of Fused Polycyclic Heteroaromatic Compounds

Abstract

Thirty-six new stabilised phosphonium ylides designed to undergo thermal loss of Ph3PO and radical domino cyclisation have been prepared and are generally found to undergo the desired reaction under flash vacuum pyrolysis conditions at 850 °C. A wide range of ­tetra- and pentacyclic fused-ring heterocycles, many previously unknown, are thus formed in moderate to high yield in a single step. By using suitably substituted starting materials, substituents such as CH3 and Cl can be installed at various positions in the products. The method has also been demonstrated in a combinatorial mode to generate a small library of twelve fused-ring heterocycles in a single pyrolysis.