Carbon flatland: Planar tetracoordinate carbon and fenestranes

An overview is given of the more recent results in the wider area of planarizing distortions of tetracoordinate carbon. Topics discussed include computational results, structural landscape between tetrahedral and planar carbon, planar tetracoordinate carbon in stable metal complexes and recent syntheses of fenestranes. Under computational results, focus is on computational methods, stereomutation of planar tetracoordinate carbon, 'brave new world' of C25, planar tetracoordinate carbon tamed by metal complexes, planar hypercoordinate carbon-boron cages and resonance structures and MO Approach. As for structural landscape, emphasis is on spiroalkanes and fenestranes, pyramidanes and strain and stability. Finally, the fenestranes covered include (1) trans,cis,cis,cis-[5.5.5.5]fenestrane, (2) all-cis-[3.5.5.5.]-1-azafenestrane, (3) all-cis[5.5.5.5]-1-azafenestrane, (4) all-cis-[4.5.5.5]-1-azafenestrane, (5) bennzannulated fenestranes, (6) transition-metal-induced formation of fenestranes, (7) enhanced planarizing distortions and (8) laurenene - a natural [5.5.5.7]fenestrene.