Synthesis of fused tetracyclic spiroindoles via palladium-catalysed cascade cyclisation†
Abstract
Efficient palladium-catalysed cascade cyclisation to form spiroindoles is developed. Treatment of indoles bearing a propargyl chloride side chain at the 3-position with various external nucleophiles in the presence of a catalytic amount of Pd2(dba)3·CHCl3/dppb and Cs2CO3 in THF gives fused tetracyclic spiroindoles in moderate to good yields.