Prismanes, synthesis

Formal [27t + 2ff + 2homo-homo-Diels-Alder) reactions include the cycloaddition of 4-phenyl-l,2-4-triazoline-3,5-dione to benzvalene (7), which served as the key step in the Katz prismane synthesis, and TCNE to 2-exo-methyl-endb-tricyclo[3.2.1.0 ]oct-6-ene (55). ... 

Stereoselectivity. See Asymmetric induction Axial/equatorial-, Cis/trans-, Enantio-, Endo/exo- or Erythro/threo-Selectivity Inversion Retention definition (e.e.), 107 footnote Steric hindrance, overcoming of in acylations, 145 in aldol type reactions, 55-56 in corrin synthesis, 261-262 in Diels-Alder cyclizations, 86 in Michael type additions, 90 in oiefinations Barton olefination, 34-35 McMurry olefination, 41 Peterson olefination, 33 in syntheses of ce-hydrdoxy ketones, 52 Steric strain, due to bridges (Bredt s rule) effect on enolization, 276, 277, 296, 299 effect on f3-lactam stability, 311-315 —, due to crowding, release of in chlorophyll synthesis, 258-259 in metc-cyclophane rearrangement, 38, 338 in dodecahedrane synthesis, 336-337 in prismane synthesis, 330 in tetrahedrane synthesis, 330 —, due to small angles, release of, 79-80, 330-333, 337... 

Photoelimination of nitrogen from 1-pyrazolines has also been employed in the synthesis of tricyclo[3.2.1.02,4]oct-6-ene,338 prismane,339 quadri-cyclane,340 snoutene ,341 and marasmic acid.342 The trimethylenemethanes 414 have been prepared by photolysis of azoalkanes 415 and characterized spectroscopically.343 Dimerization and cycloaddition to alkenes of these biradicals have been reported.344... 

Photolysis of an azo compound provided the first synthesis of prismane, albeit in very low yield (2.36)259). 

One example of this strategy is the synthesis of the Mo(C0)3-capped [FegSgLg] clusters described in detail by Coucouvanls elsewhere in this volume (74). In this approach, the triply-bridging sulfides of an [FegSgLg] prismane act as a tridentate... 

Proof for the existence of benzene isomers in irradiated benzene has been obtained in several ways. These will not be discussed in detail, but they may be classified broadly as physical and chemical. Nuclear magnetic resonance has been used by Wilzbach and Kaplan to identify benzvalene.39 Prismane has also been identified by NMR and by vapor-phase chromatography. The Dewar form has been synthesized in several steps which start with ris-1,2-dihydrophthalic anhydride. Photochemically this compound yields bicyclo(2,2,0)hexa-5-ene-2,3-dicarboxylic aqid anhydride. This was followed by catalytic reduction and oxidative decarboxylation to give the Dewar form of benzene.39 The method of synthesis alone provides some basis for structure assignment but several other bits of supporting evidence were also adduced. Dewar benzene has a half-life of about 48 hr at room temperature in pyridine solution and its stability decreases rapidly as the temperature is raised. 

Katz, T.J. and Acton, N. (1973) Synthesis of prismane.Journal of the American Chemical Society, 95, 2738-2739. 

In 1982, the synthesis and properties of a new polycyclic C2oH2o hydrocarbon, dodecahedrane, was reported [21], The twenty carbon atoms of this molecule are arranged like the vertices of a regular dodecahedron. When, in the early 1960s, H. P. Schultz discussed the topology of the polyhedrane and prismane molecules (vide infra) [22], at that time it was in terms of a geometrical diversion rather than true-life chemistry. Since then it has become real chemistry. 

T. J. Katz, N. Acton, Synthesis of Prismane. J. Am. Chem. Soc. 1973, 95, 2738-2739 V. Ramamurthy, T. J. Katz, Energy-Storage and Release -Direct and Sensitized Photoreactions of Dewar Benzene and Prismane. Nouv. J. Chim. 1977, 1, 363-365. 

From a purely synthetic viewpoint, triazolinedione adducts have served as substrates for gaining access to numerous target molecules such as prismane, semibullvalene, bridged semibullvalenes, elassovalene, caged compounds, and azoalkanes. Indeed, the title reagent can be used not only as a chiral source, but also as an azo donor. In the synthesis of 4,5-diazatwis-4-ene, for example, (-)- nfirst step involved cycloaddition to cyclooctatetraene dibromide with formation of a separable mixture of diastereoisomers. Eventual removal of the... 

The reaction of 1,-phenyl-1,2,4-triazolinedione occurs at the 1,4-position of the vinylcyclopropane system of benzvalene. This reaction has been used for the synthesis of prismane as mentioned before 39) (see Eq. 37). 

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