Congressane

Abstract

The observed product ratio favoring I1 can be rationalized, at least qualitatively, in terms of less steric hindrance about the carbonyl groups with respect to solvation, fewer nonbonded hydrogen repulsions, and less ring strain. The steric hindrance about the carbonyl group in I is dramatically demonstrated by its lack of reactivity6 toward hydroxylamine. In contrast, under normal conditions the ketone I1 is easily converted to the corresponding oxime, 3. 90 % yield, m.p. 135-136"; Y N~,~~ 3226, 3125, and 1667 cm.-l. The n.m.r. spectrum shows a typical C-8 endo-proton doublet centered at T 8.72, J1 = -13 C.P.S. and J2 = -4 c.P.s., and a broad peak at T 6.74 (-0-H).We visualize the isomerization reaction as a transannularly assisted abstraction of a hydrogen atom from C-5 to form the carbanion Ia. Because of the proximity, the anion adds to the carbonyl group to form the bird-cage alkoxide anion IIIa, a transannular enolate anion, which is thermally unstable at the reaction temperature with respect to the less strained species Ia and IIa. Protonation of the anions then provides the thermodynamically controlled mixture of the ketones I and 11. No alcohol I11 could be found in the reaction products.The Crystal and Molecular Structure of Congressane, C14H20) by X-Ray Diffraction Sir :A structure analysis by X-ray diffraction of the material described in the accompanying communication by Cupas, Schleyer, and Treckerl has verified that the material is congressane (I).A fragment of a large octahedron grown from petroleum ether was mounted on the a axis and was used to take eight layers of equi-inclination Weissenberg photographs with Cu K a radiation. Visual estimates were ( I ) C. Cupas, P. von R. Schleyer, and D. J. Trecker, J . Am. Chem. SOC., 87, 917 (1965):

Functionalized Nanodiamonds Part I. An Experimental Assessment of Diamantane and Computational Predictions for Higher Diamondoids

“…Lower diamondoids involve diamantane (1, synthesized [2] and isolated from petroleum [27] in the 1960s); triamantane (2) [4] and C 2h -tetramantane (anti-tetramantane, 4), [5] which were prepared synthetically and were also isolated from petroleum recently. C 2 -Tetramantane (skew tetramantane, 3), C 3v -tetramantane (isotetramantane, 5), T d -pentamantane (6), [12] and D 3d -hexamantane (cyclohexamantane, 7) [13] are currently only available from petroleum.…”

“…[1] Analogous thermodynamically controlled isomerizations of norbornene [2] or norbornadiene [3] dimers were used for the preparation of diamantane, the next representative diamondoid. Unfortunately, the "stabilomeric" approach is not efficient for the preparation of higher diamondoids (i.e., larger than tetramantane) because these possess multiple, energetically close, low-lying minima so that mixtures of isomers ensue.…”

Cyclic Diamondoid Structures with Shared Vertices, Edges, or 6-membered Rings

“…Their isolation and purification are based on their high stability towards heat and oxidation. Schleyer and coworkers discovered that adamantane (C 10 H 16 ), 4 diamantane (C 14 H 20 ), 5 and triamantane (C 18 H 24 ) 6 can be obtained synthetically by Lewis-acid or transition-metal catalyzed rearrangements of polycyclic isomers; the driving force in such reactions is based on the fact that diamondoids have appreciably lower steric strain in comparison with all other polycyclic isomers. However, only one of the three isomeric tetramantanes could be obtained by this approach, 7 so that for higher diamondoids the only source at present is the isolation from petroleum.…”

NMR spectral properties of the tetramantanes – nanometer‐sized diamondoids

“…[20] Diamantane, 2, the two-cage, second member of the diamondoid series, also has only secondary and tertiary carbons. [21,22] Quaternary carbons appear beginning with the three-cage triamantane, 3, Fig. 1, Table 1.…”