The bond between inverted carbon atoms. Synthesis and chemistry of 2,4-methano-2,4-didehydroadamantane: a highly reactive [3.1.1]propellane

Nature of Bonding in [3.1.1]Propellane. Vibrational Spectra and Normal Coordinate Analysis of 2,4-Methano-2,4-didehydroadamantane, 2,4-(Dimethylmethano)-2,4-didehydroadamantane, and Their Dihydro Congeners

“…[3.1.1]Propellanes 1 and 2 as well as their dihydro congeners 3 and 4 were synthesized following the literature procedures. , The samples of 1 and 2 were prepared in a drybox under nitrogen. For Raman spectroscopy capillary tubes were filled with the neat sample and spectra were recorded immediately after.…”

“…Contrary to the usual carbon−carbon single bond, the central bond in small-ring propellanes, such as in 2,4-methano-2,4-didehydroadamantane ( 1 ) and 2,4-(dimethylmethano)-2,4-didehydroadamantane ( 2 ) (Figure ), is highly reactive toward electrophiles and free radicals. − The bond in 1 and 2 can easily be reduced by electron-transfer hydrogenation to give 2,4-methanoadamantane ( 3 ) and 2,4-(dimethylmethano)adamantane ( 4 ), respectively. , Also, [3.1.1]propellanes 1 and 2 readily add disulfides and carbon tetrachloride across the central bond to give the corresponding 2,4-disubstituted 2,4-methanoadamantanes . The unusual chemical reactivities of 1 and 2 have been attributed to the electron-density distribution in the central propellane bond. , Whereas chemical evidence indicates that the electron density on the central bond of small propellanes is considerably higher at the back side of the inverted carbon atoms than between them, more substantial support of this hypothesis was needed. Therefore, we have undertaken a detailed vibrational study of the two [3.1.1]propellane derivatives, 1 and 2 , and their dihydro congeners, 3 and 4 , and determined the changes in energies, geometrical parameters, and normal modes due to the formation of the propellane bond.…”

Synthesis of propellane-containing natural products

“…In addition to Wiberg's results, other theories have also been suggested. 18,[24][25][26][27] Ginsburg [28][29][30] and Wiberg 19,31,32 have reviewed the syntheses and the theoretical studies of propellanes extensively, Wiberg concentrating on the small-ring propellanes and Ginsburg on the medium-sized rings. In his book entitled 'Propellanes', Ginsburg even describes the syntheses and structures of natural products possessing the propellane structure.…”

Photoelimination of nitrogen from adamantane and pentacycloundecane (PCU) diazirines: a spectroscopic study and supramolecular control †

“…9 We became interested in carbenes as intermediates during the preparation of strained polycyclic molecules, 10 particularly propellanes. 11,12 Convenient precursors for photochemical or thermal formation of carbenes are diazirine derivatives. 13 Elimination of nitrogen occurs upon photochemical excitation or at elevated temperatures, thus delivering carbenes.…”