Propellanes structure

Jamrozik decided between the two on the basis of what he himself regards as a tenuous argument involving UV spectroscopy. The arguments based on NMR spectroscopy support the propellane structure shown, 60, rather than the one with a cis-arrangement 62 of the abovementioned hydrogens ... 

For a review of these compounds until 1975, cf. Ginsburg, D. Propellanes. Structure and Reactions , Verlag Chemie, Weinheim, 1975, pp. 30-53... 

Previous reviews of [1.1. l]propellane chemistry were written by Ginsburg5, Wiberg 6 and Tobe7. The present review is intended to provide a comprehensive and updated survey of the structure, properties, synthesis and reactions of [l.l.l]propellanes. Structures of all known compounds of this class are shown in Chart 1. 

Several other vibrational modes are characteristic of the propellane structures, such as the C—H stretching vibrations of the CH2 groups at the nearly constant frequencies of 3000 cm 1 (symmetric) and 3060 cm"1 (antisymmetric), almost the same as in cyclopropane itself (see Table 4). 

Sulfuration of acenaphtho[l,2- ]acenaphthylene 80 with elemental sulfur (1 molar amount as Sg) in DMF at 130°C gave the pentathiepane 7, with a [5.3.3]propellane structure, as the sole product, in 88% yield (Scheme 15) <1998TL2605, 1999EJ0597>. In the case of 3-phenylacenaphtho[l,2- ]acenaphthylenes 83, pentathiepanes were separated as a mixture of two conformers 8 and 9 in the equilibrium ratio of 55 45. Both isomers 8 and 9 slowly isomerized into each other in solution at room temperature. 

Both Sn5(2,6-Et2C6H3)6 and Sn7(2,6-Et2C6H3)s have a pentastanna[ 1.1.1] propellane structure, which consists of three fused three-membered rings, as shown in Figs. 14.7.3(g) and (h). In these two compounds, the bridgehead Sn atoms each have all four bonds directed to one side of the relevant atom, thus forming inverted configuration Sn- Sn bonds, the distances of which... 

Ginsburg, D. Propellanes, structure and reaction Weinheim Verlag Chemie 1975... 

On the other hand, cyclization of bis-l, 3-dienes with the propellane structure depends on the ratio of the reagents. Starting from I equivalent of nitroso compound, the monoaddition product 4 is formed exclusively as a syn/anti mixture (66 34), whereas with an excess of the nitroso compound, the product resulting from the double addition is formed as a complex diastereomeric mixture16. 

A paper well worthwhile reading on this subject discusses the energies of optimized structures of various monocyclic, bicyclic and tricyclic propellane structures by the 4-3IG and 6-31G basis sets , including [2.2.1], [2.1.1] and [l.l.l]propellanes which concern us here. Energies of hydrogenolysis of their conjoining bonds have been calculated and compared with experimental results. These become more negative in the order [1.1.1],... 

D. Ginsburg, Propellanes—Structure and Reactions, Verlag Chemie, Weinheim, 1975. 

Cyclopropanes without electron-withdrawing substituents usually resist the attack of nucleophiles. Exceptions are strained systems and a-halo-substituted derivatives which undergo homoallylic substitution reactions.[l.l.l]Propellane structures, though usually formed only as intermediates, underwent addition of benzenethiol with cleavage of the central cyclopropyl bond. This addition possibly follows a radical chain mechanism. 

Fig. 4. The propellane structures and the planes of sections containing the bridge and bridgehead (C ) atoms for the contour diagrams of Fig. 5 [29].

C,sH24, Mr 204.36, oil, bp. 65-70°C (33.3 Pa), [aJo -15.8° (CHCI3). A natural triquinane hydrocarbon with a [3.3.3]propellane structure from Isocoma wrightii (Asteraceae), an indigenous species of south west USA toxic to cattle and sheep, from South African Berkheya species, and the roots of Senecio isatideusK Derivatives of M. show antiproliferative activity. ... 

Fig. 12.9 The five notable CH4 structures (two are shown for propellane CH4), MP2/6-31G geometries (ef. Fig. 12.8). Tetrahedral CH4 is the only real molecule here and the standard with which the others are compared. Planar and pyramidal CH4 are stationary points. The half-planar structure shown is a minimum along its distortion curve but is not a stationary point. No propellane structure is a distortion minimum or a stationary point the 60° structure shown has an HCH angle similar to the corresponding CCC angle calculated for 30, [1.1.1 (propellane. The MP2/6-31G energies in hartrees (atomic units) and relative energies (kJ mol , in parentheses) are given...

Figure 12.13). Propellane CH4 has no minimum energy arrangement along the distortion curve in which three C-H bonds are swivelled toward a central bond (Fig. 12.8). The transition from tetrahedral to propellane CH4 occurs when three C-H bonds are in a plane, with the fourth bond normal to the plane, and this is the lowest-energy propellane structure. The species with HCH angles 60° (Fig. 12.9), similar to those in the known propellane (30, [21, 22], 58.2° from an MP2/6-3IG optimization) was analyzed in a matmer similar to the above four CH4 stmctures. 

D. Ginsburg, Propellanes, Verlag Chemie, Weinheim, 1975 Propellanes Structure and Reactions, Sequels I and II, Technion, Haifa, 1981, 1985 D. Ginsburg, in The Chemistry of the Cyclopropyl Group (Ed. Z. Rappoport), Wiley, Chichester, 1987, pp. 1193-1221. 

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