Stereospecific and stereoselective rhodium(I)-catalyzed intramolecular [2+2+2] cycloaddition of allene-ene-ynes: construction of bicyclo[4.1.0]heptenes.

Treatment of the allene-ene-yne substrates with [{RhCl(CO)2}2] effected the intramolecular [2+2+2]-type ring-closing reaction to produce various of tri- and tetracyclic derivatives containing a cyclopropane ring. The reaction is highly stereoselective as well as stereospecific with good to excellent yields.

C(sp3)-C(sp3) and C(sp3)-H bond activation of 1,1-disubstituted cyclopentane.

The unprecedented C(sp(3))-C(sp(3)) bond cleavage of unactivated cyclopentane has been achieved. Rh(I)-catalyzed cycloaddition of allenylcyclopentane-alkynes produced in situ the 9-cyclopentyl-8-rhodabicyclo[4.3.0]nona-1,6-diene intermediates, which subsequently underwent [7+2] cycloaddition via ß-C elimination, affording bicyclo[7.4.0]tridecatriene derivatives in good yields. Changing the Rh(I) catalyst effected the Cγ-H bond activation of the common 9-cyclopentyl-8-rhodabicyclo[4.3.0]nona-1,6-diene intermediate to produce the novel spiro[2.4]heptane skeleton in a site-selective manner.