Planar carbon octaplane

The most likely abode that has been devised for a planar carbon atom, dimethano-spiro[2.2]octaplane (4), poses a formidable synthetic challenge by virtue ( ) of its... 

A series of computer experiments by Radom and Rasmussen iderrtified prorrrising candidates for perfectly-planar-carbon molectrles, the most prorrrising of which were dimethanospiro[2.2]octaplane arrd dimethanospiro[2.2]binorraplane. Becanse of their size, complexity, and the strain inctrrred by planar carborr, these compotrrtds represent formidable synthetic challenges nevertheless, it is conceivable that they could yield to a thorough retrosynthetic analysis followed by skillful implementation of one of the thus-revealed putative routes. 

To return now to the examination of octaplane and its more-constrained siblings. The optimized HF/6-3 lG(d) stmcture of octaplane (the PES minimum) has a CCC angle of 169°, approaching the 180° an e of planar caibon (the tetralre-dral angle is of course 109.5°). However, the central carbon of this S4 stmctiue showed considerable reluctance to flatten to planarity (C4h), as revealed by an... 

This study of dimethanospiro[2.2]octaplane must leave tittle doubt that its central carbon is either perfectly planar, or that the barrier to planarization is very small, in which latter case the relative-minimum species probably has a nearly-planar central carbon (one longs for the day when computer power will permit a CCSD(T) [37,38] optimization/frequency calculation with a 6-31G(d) or bigger basis on a molecule like this). Radom and Rasmussen followed this discovery of the very promising... 

Fig. 1.12 An elaboration on the concept shown in Fig. 1.11. Retrosynthetic analysis of dimeth-anospiro[2.2]octaplane (4) leads here to 10, and then to 11, which is depicted more realistically as 12, with a tetrahedral, rather than a planar, central carbon. The carbonyl groups shown are only suggestive of the synthetic handles that might be used to manipulate carbon-carbon bondmaking...

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