Catalytic one-pot synthesis of [5.5.5.6]fenestrane systems via a dicobalt octacarbonyl-catalyzed tandem cycloaddition of dienediynes.
Catalytic one-pot synthesis of fenestrane derivatives from dienediynes was developed: fenestranes were synthesized in high yields by a dicobalt octacarbonyl-catalyzed tandem cycloaddition of dienediynes.
A quick access to the spirotricyclic core analogue of mangicol A by a Rh(I)-catalyzed tandem Pauson-Khand/[4+2] cycloaddition.
Highly chemoselective and stereoselective tandem Pauson-Khand/[4+2] cycloaddition leads to efficient construction of the spirotricyclic core analogue of mangicol A.
On the planarity of tetracoordinate carbon enclosed by annulene perimeters
Abstract Proposals that planar tetracoordinate carbon might be achieved by enclosure in an annulene perimeter have been examined by means of MNDO calculations. Unfortunately, the lowest energy forms of 1–3, and 5 are indicated to distort as far away from planarity as possible, consistent with the strain demands of the carbon skeletons. Even in hypothetical stereomutation transition states, planar tetracoordination around the central carbon should be energetically difficult to achieve in these hydrocarbons, which, at best, are expected to be unstable strained polyolefins. Planar tetracoordinate carbon is more likely to be achieved when both π and σ systems provide effective stabilization through multicenter bonding. Several illustrative proposals for experimental examination are presented.