Tricyclopropylamin und sein Radikalkation

Titanium-mediated syntheses of cyclopropylamines

“…As reported by the same group, this efficient transformation can also be carried out with substoichiometric amounts of Ti(OiPr) 4 (5-10 mol%) [57,58]. Four years later, development of a very useful and highly versatile preparation of cyclopropylamines was initiated by de Meijere et al [59][60][61][62][63][64][65][66][67][68]. N ,N -Dialkylaminocyclopropanes (11) with up to three additional substituents are readily obtained from carboxylic acid N ,N -dialkylamides (8) and ethyl-as well as substituted ethylmagnesium halides in the presence of titanium tetraisopropoxide or, even better, methyltitanium triisopropoxide.…”

“…Thus, the theoretically interesting tricyclopropylamine [63,64] could be prepared from benzylcyclopropylformamide in a sequence of reductive cyclopropanation of the formyl group, hydrogenolytic debenzylation, N -formylation and repeated reductive cyclopropanation [63,64].…”

Tetracyclopropylmethane: A Unique Hydrocarbon with S4 Symmetry

“…[4] Because of the extreme steric bulk and electron-donating properties of the tris(trimethylsilyl)-methyl ligand, this compound is monomeric with a bent coordination geometry at the two-coordinate calcium center. [4] By employing the moderately bulky, multidentate, oxygensubstituted anionic phosphanes I and II, we were able to synthesize and structurally characterize a sodium trialkyl calcate(ii) (with the monoanionic ligand I) and a calcium organyl with a heterocubane structure (with the dianionic ligand II). Soft ligands (such as phosphanes) have been shown to be best suited for complex formation with the hard alkali and alkaline earth metals when they are anionic.…”

“…[1±4] Nevertheless, the corresponding carbon compound, tetracyclopropylmethane (7 a), has remained elusive. Neither the two commonly used approaches to percyclopropylated element derivatives, [5] nor the methods for the preparation of tricyclopropylamine [4] can be used to form 7 a. An attempted direct geminal biscyclopropylation of dicyclopropyl ketone with in situ generated [Cpr 2 TiCl 2 ] [6] analogous to the reported geminal bismethylation of ketones with [Me 2 TiCl 2 ] [7] only led to tricyclopropylmethane in a moderate yield (34 %).…”

Tetracyclopropylmethan: ein einzigartiger Kohlenwasserstoff mitS4-Symmetrie

“…[1] Theoretische Betrachtungen haben gezeigt, dass diese Stereoselektivität nicht von sterischen, sondern viel-mehr von elektronischen Faktoren kontrolliert wird. [2] Diese Voraussage konnte bisher nur für CHO-, COCl- [3] und CF 3 -Substituenten [4] belegt werden, CO 2 Et- [5] und CN-Gruppen [6] dagegen begünstigen die Drehung nach auûen. B. eine Hydroxygruppe, als Substituent in der 3-Position begünstigt eine Drehung nach auûen.…”