title: Phosphinofenchol or metastable phosphorane? Phosphorus derivatives of fenchol.
abstract: Not the expected phosphinofenchol 1 but phosphorane 2 is obtained after reaction of 2-lithio(diphenylphosphino)benzene with (-)-fenchone. Surprisingly, ONIOM(B3LYP/6-31G*:UFF) computations of 1 and 2 as well as B3LYP analyses of smaller model systems point to a lower thermodynamic stability of phosphoranes relative to their isomeric alkoxyphosphines. An analogue inherent instability is computed for the methylphosphorane 10, which is also synthesized and characterized by X-ray analysis. Decreasing ring size in cyclic phosphoranes, that is, from five- to four-membered ring systems, destabilizes cyclic phosphoranes even more. This computational prediction is verified experimentally by reaction of lithiomethyl(diphenylphosphine) with (-)-fenchone and subsequent isolation of the corresponding phosphinofenchol. Protonation or alkylation of phosphoranide intermediates can account for the formation of metastable phosphoranes.
authors.affiliation: Organisch-Chemisches Institut der Universität Heidelberg, Germany. bernd.goldfuss@urz.uni-hd.de
authors.forename: B
authors.initials: B
authors.lastname: Goldfuss
authors.forename: T
authors.initials: T
authors.lastname: Löschmann
authors.forename: F
authors.initials: F
authors.lastname: Rominger