Synthesis of fused-ring indenes by ruthenium-catalyzed ring-closing metathesis

The preparation of new 1, 2-unsymmetrically substituted fused-ring indenes from dialkenyl precursors by utilization of the ruthenium-catalyzed ring-closing metathesis is described. By analogous strategy, 1,3-substituted fused-ring indenes with medium-ring sizes have also been synthesized. For bis(allylsilyl)indene, the formation of a 1,3-fused ring appears to be prevented by ring strain and a 1,1-spiro compound is obtained instead due to rearrangement of the substituents. The rearrangement is enabled by the [1,5]-silatropic shifts operating in silyl-substituted cyclopentadienyl compounds. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheirn, Germany, 2006).