A ‘sugar-coated’ carbene precursor: a single crystal X-ray diffraction and NMR study

Molecular dynamics simulations of beta-cyclodextrin-aziadamantane complexes in water

Force-field-based atomistic simulations of host-guest supramolecular complexes between beta-cyclodextrin and several aziadamantane derivatives have been analyzed with respect to relative orientation and interaction energies, explicitly considering solvent (water) molecules. For each case, the calculations revealed two stable orientations of the guest within the host that are different in interaction energy. Fluctuation of and correlation between characteristic properties were analyzed. Among other things, it turned out that orientation angle and inclusion depth are clearly correlated. In addition, for the unsubstituted aziadamantane, the enthalpy of complex formation was calculated and compared to experimental results.

Supramolecular Recognition and Structural Elucidation of Inclusion Complexes of an Achiral Carbene Precursor in β- and Permethylated β-Cyclodextrin

[structure: see text] Inclusion of achiral carbene precursor endo-8-azibicyclo[3.2.1]octan-3-ol (1) in chiral beta-cyclodextrin (7-Cy) and tri-O-methyl-beta-cyclodextrin (TRIMEB) leads to 1:1 complexes 1@7-Cy and 1@TRIMEB, respectively. The combined methods of induced circular dichroism, NMR spectroscopy, and X-ray structure determination were employed for the first time for structural elucidation of the complexes in solution and the solid state. Significantly different orientations of 1 were observed. Compared with 1@7-Cy, 1@TRIMEB exhibits a different guest orientation and an association constant one-twentieth lower.

Reversal of diastereoselectivities in intra- and intermolecular reactions of 2-adamantanylidenes primarily caused by electron-donating and electron- withdrawing substituents on C5

[reaction: see text] A reversal of diastereoselectivity was observed for novel 5-(trimethylsilyl)adamantan-2-ylidene (1c) with regard to 5-hydroxyadamantan-2-ylidene (1a). Ostensibly in intermolecular reactions, 5-substituted 2-adamantanylidenes (1) are sterically unbiased. However, inductive effects originating from the pendant group bend the divalent carbon bridge of 1 either toward (ERG's, e.g., -Si(CH(3))(3)) or away from (EWG's, e.g., -OH) the gamma-position. Hence, the more exposed side is more susceptible to intermolecular reaction and the other side concomitantly undergoes intramolecular 1,3-CH insertions more readily.

2,6-Diaziadamantane: a single-crystal X-ray diffraction study and theoretical calculations

The first single-crystal X-ray diffraction study of 2,6-diaziadamantane (2), a compound containing two diazirine functionalities, and B3LYP/6-311+G* and MP2/6-311+G* calculations relating to the interaction between carbon-nitrogen and nitrogen-nitrogen covalent bonds and electron density within the diazirine rings have been performed. In addition, the protonation of 2-aziadamantane (1) has been investigated. The single-crystal X-ray diffraction study of 2, including UV/vis titrations of 1, corroborate the theoretical conclusion that the low basicity can be attributed to a rehybridization of the nitrogen lone pairs. Moreover, the strain in diazirine is unusually small.