Simmons-Paquette molecule

Using this theorem we can prove that various molecular graphs are intrinsically chiral. We shall illustrate by proving that the graphs of a ferrocenophane derivative molecule [26] and the Simmons-Paquette molecule [29, 30] are both intrinsically chiral. (Note that Liang and Mislow observed the intrinsic chirality of this ferrocenophane derivative as well as many other molecules [21].)... 

Figure 16. Some topologically chiral molecular graphs, (a) The Simmons-Paquette molecule.74 (b) Walba s 3-rung Mobius ladder molecule.75 (c) [4](l,l )[4](3,3 )[3](4 4 )-Ferrocenophan-16-one.76 (d) Triple-layered naphthalenophane.78 Unlabeled vertices represent carbon atoms, and hydrogen atoms are suppressed for clarity. Only one enantiomer of each molecule is shown.

The synthesis of 79, 80 and related spiranes has been of interest because of their potential conversion to centrohexacyclic derivatives bearing three additional bridges across the neopentane carbon atoms C-9, C-10 and C-l l,in analogy to some unusual non-benzoannelated analogues such as the Simmons-Paquette molecule [37,81,82]. In fact, triptindanetrione 72 has been used in several cases to construct three additional five-membered rings (Schemes 15 and 56). A surprisingly efficient three-fold bridging with aliphatic diatomic units has been achieved by treatment of 72 with an excess of lithium acetylides. In this way, centrohexacyclic triptindanes 81-83 and related compounds have become accessible, as shown in Scheme 15 [83]. 

At the time they were synthesized, these molecules were not recognized as having a non-planar graph, and actually the first topologically chiral K5 molecule recognized as such, is the centered polyquinane derivative 53, independently synthesized by H. E. Simmons and J. E. Maggio [80] on the one hand, and by L. A. Paquette and M. Vazeux [81] on the other hand (Fig. 9). That it is topologi-... 

The secondary marine metabolite (+)-acetoxycrenulide has unprecedented structural features which prompted L.A. Paquette et al. to embark on its total synthesis. The eight-membered carbocycle of the target was constructed via a Claisen rearrangement. The bicyclic p,y-unsaturated lactone was subjected to Simmons-Smith conditions, that delivered the cyclopropyl ring exclusively from the p-face of the molecule as a result of the predominant ground-state conformation. 

In the absence of a directing group, the cyclopropanation of cyclic olefins is generally under steric control. The stereochemical preference can be predicted from the ground state conformation of the molecule and often high levels of stereocontrol are observed. For example, Paquette and coworkers used a Simmons-Smith reaction in their total synthesis of the secondary marine metabolite (+)-acetoxycrenulide (30), whereby high P-face selectivity was observed. ... 

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