1253597-20-4Relevant academic research and scientific papers
Discovery and synthetic value of a novel, highly crowded cyclopentadienylphosphane Ph2P-CpH and its ferrocenyl-bisphosphane dppf
Petrov, Alex R.,Elfferding, Michael,Moebus, Juri,Harms, Klaus,Rufanov, Konstantin A.,Sundermeyer, Joerg
, p. 4157 - 4165 (2011/01/09)
Base-catalysed condensation of Ph2P-C5H5 (1) with an excess of acetone leads to a fulvene-like diphenyl(4,4,6-trimethyl- 4,5-dihydropentalen-2-yl)phosphane Ph2P-C11H13 (3) as a product of double condensation. Carbometallation of 3 with MeLi, followed by aqueous work-up, results in formation of a new cyclopentadienylphosphane bearing a highly sterically demanding, anellated 1,1,3,3-tetramethylcyclopentane moiety (4, Ph2P-CpH). It reacts with chalcogene oxidants (H2O2, S8, Se) to form the corresponding phosphane chalcogenides Ph2P(=X)CpH, X = O (5), S (6), Se (7) in high yields. Quatemization of 4 with MeI gives the phosphonium salt 8 as a single isomer in high yield. Dehydrohalogenation of 8 by reaction with nBuLi gives Cp-phosphonium ylide Ph2P(Cp )Me (9). An alternative protocol towards 9 that includes deprotonation of 8 with benzylpotassium followed by P-alkylation is superior and gives 9 in more than 95% yield. Staudinger reaction of 4 with tBuN3 gives only P-arnino-cyclopentadienylidenephosphorane Ph2P(Cp)-NHtBu (10), whereas with Me3SiN3 only the tautomeric P-imino-cyclopentadienylphosphane Ph2P(NSiMe3)CpH (11) was isolated. Hydrolysis of 11 with wet MeCN leads to the new parent P-arnino-cyclopentadienyhdenephosphorane Ph2P-(Cp)NH 2 (12). Treatment of 4 with benzylpotassium followed by transmetallation with FeCl2 leads to the sterically most crowded ferrocenyl-bisphosphane [{Ph2P-Cp}2Fe] (13, dppf) in high yield. Its X-ray diffraction analysis reveals an anti-orientation of phosphane functionalities at both cyclopentadienyl rings. However, upon reaction of dppf with [PdCl2(MeCN)2], a constrained syn-orientation is achieved in the product [[dppf] PdCl2] (14). Halogen exchange by reaction of 14 with NaI leads to the corresponding [{dppf}PdI2] (15). Molecular structures of 4, 9, 13 and 15 have been confirmed by XRD studies.
