Bowl-shaped structures

Our goal in those days was to find a new Jt-system more aromatic than king benzene. Then came the news of the corannulene (6) synthesis by Barth Lawton (1966) and its bowl-shaped structure quickly aroused strong interest among us. As is mentioned below, analysis of its structure logically led us to conceive the extrapolation of its structure to a sphere so that we could envisage three-dimensional delocalization of the 7t-electrons. Fortuitously about that time my small son started... 

Naiki, M. Shirakawa, S. Kon-i, K. Kondo, Y. Maruoka, K. Tris(2,6-diphenylbenzyl)amine (TDA) and tris(2,6-diphenylbenzyl)phosphine with unique bowl-shaped structures synthetic application of functionalized TDA to chemo-selective silylation of benzylic alcohols. Tetrahedron Lett. 2001, 42, 5467-5471. 

A single crystal X-ray diffraction analysis has been carried out on both the chloro- and the phenyl-substituted subphthalocyanines 2.284 and 2.287 (Figures 2.3.2 and 2.3.3). These analyses served to show that subphthalocyanines lie in a bowl-shaped conformation. This is, of course, very different from the near-planar conformation of the parent phthalocyanines. Presumably, this bowl-shaped structure accounts, in part, for the decreased molar absorptivities of the subphthalocyanines relative to their phthalocyanine parents . Nevertheless, despite the non-planar nature of these macrocycles, the subphthalocyanines are capable of supporting an induced diamagnetic ring current (as judged by NMR spectroscopy). Thus, they may appropriately be considered as being aromatic. 

Figure 2.21 Synthesis of circumtrindene (II) from trichlorodecacyclene (I). The bowl-shaped structure represents 60% of the fullerene cage.

When the same reaction was carried out in methanol the macrocyclic species [Cu4(pprd)4(C2H4)4] (PP6)4 (11) was formed instead. The crystal structure of this metallo-assembly revealed a bowl-shaped structure with the PFe" anion positioned at its centre (see Fig. 3). 

We synthesized the bowl-shaped bicyclic cyclophane, Ar X (Figure 11.4) and applied it to the stabilization of a sulfenic acid. " X-ray analysis of bromide 6 indicated that this cyclophane has a shallow bowl-shaped structure with a diameter of -1.4 nm (Figure 11.5). The arenesulfenic acid 8 was synthesized by solid-state pyrolysis of butyl sulfoxide 7 and isolated as stable crystals (Scheme 11.5). The effect of peripheral steric protection due to the bowl-shaped framework was illustrated by the... 

ESR) spectra indicated smaller hyperfine coupling constants for 41 compared to conventional triarylborane radical anions, consistent with more broadly delocalized spin in the constrained species. Crystallographic data revealed the radical anion to possess a shallow bowl-shaped structure in the solid state, which was shown computationally to be very close in energy to the planarized geometry (0.70kcalmol ). 

X-ray crystal structure of sumanene clearly shows the bowl-shaped structure (Fig. 3.31). The bowl depth defined as a distance between a plane of a hub benzene ring and a rim aromatic carbon is 1.11 A [125]. Sumanene favors a stacking structure in a concave-convex fashion. Each layer of the column is stapled in a staggered fashion. Every column is oriented in the same direction giving polar crystals (Fig. 3.31) [125]. Solid state NMR is also studied [126]. 

The synthesis of mono- and trioxosumanenes 54-55 is performed by oxidation of benzylic positions of sumanene (Scheme 3.43) [138]. Oxosumanenes 54-55 have the extended % conjugation relative to sumanene. Imination of monooxo-sumanene 54 leads to further % extension [134, 135]. Crystal structure of mono-oxosumanene 54 shows the bowl-shaped structure and columnar packing (Fig. 3.33) [138]. In the reaction of trioxosumanene 55 with methylmagnesium bromide, it selectively attacks from outside of the bowl (Scheme 3.43). 

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