Tetracyclo dodecan

Phosphane-free palladium(O) catalysts convert 3,3-dialkylcyclopropenes to tram-. x -cyclo[3.1.0.0 ]hexane derivatives 16 as the major product together with pentacy-clo[9.1.0.0 . 0 . 0 ]dodecane derivatives (12-16%). In the presence of phosphanes, the tetracyclo[6.1.0.0 . 0 ]nonane systems 17 was formed in > 80% yield. ... 

The H-H bonding interaction is ubiquitous and has been found in a number of systems. The earliest experimental account I am aware of reporting unusually short intramolecular H- H distances is that of Ernier and Mason [42]. These authors find H- -H distances as short as 1.754(4) A and 1.713(3) A between neighbouring bridgehead hydrogen atoms in fused norbomenes based on low temperature neutron diffraction experiments [42]. Even shorter H- -H distances were suggested in another norbornene derivative on the basis of an X-ray diffraction determination (Jr h = 1-62 A) [49]. While the latter result awaits confirmation by neutron diffraction, it still indicates that norbornene or norbornane derivatives are candidates for very short, perhaps the shortest, intramolecular H- H distances. The molecular graph of the parent compound in this series (exo, exo-tetracyclo[6.2.1.1 .0 ]dodecane) obtained at the... 

Figure 9-9. The calculated molecular graph of exo, exo-tetracyclo[6.2.1.P . 0 ] dodecane which consists of two fused norbornanes rings. The H-H bond path links the nuclei of the two bridgehead hydrogen atoms. This results in the closure of two rings concomitant with the appearance of two ring critical points (yellow) and a cage critical point between them (green).

Maiti, B.C. and Lahiri, S., Tetracyclo[6.4.0.0. 0 ]dodecan-6-ones A novel construction of tricy-clo[7.2.1.0 ]dodecan-10-one skeleton by acid catalysed cyclopropyl bond cleavage. Tetrahedron, 53, 13053, 1997. 

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