Homoleptic Lanthanide Alkyl and Amide Precatalysts Efficiently Mediate Intramolecular Hydrophosphination/Cyclization. Observations on Scope and Mechanism

Abstract

Supporting InformationMaterials and Methods. All manipulations of air-sensitive materials were carried out with rigorous exclusion of oxygen and moisture in flame-or oven-dried Schlenk-type glassware on a dual-manifold Schlenk line, or interfaced to a high-vacuum line (10 -6 Torr), or in a nitrogenfilled Vacuum Atmospheres glovebox with a high capacity recirculator (< 1 ppm of O 2 ). Argon (Matheson, prepurified) was purified by passage through a MnO oxygen-removal column and a Davison 4A molecular sieve column. Pentane and toluene were dried using activated alumina columns according to the method described by Grubbs, 1 and were additionally vacuumtransferred from Na/K alloy immediately before use if employed for catalyst synthesis or catalytic reactions. Ether and THF were distilled before use from appropriate drying agents (sodium benzophenone ketyl, Na/K alloy) under nitrogen. Chloroform-d was purchased from Cambridge Isototope Laboratories. Benzene-d 6 , toluene-d 8 , and cyclohexane-d 12 (Cambridge Laboratories; all 99+ atom % D) used for NMR reactions and kinetic measurements were stored in vacuo over Na/K alloy in resealable bulbs, and were vacuum transferred immediately prior to use. All organic starting materials were purchased from Aldrich Chemical Co. or Lancaster Synthesis Inc., and were used without further purification unless otherwise stated. Substrates 3, 5, 7, 9, 11 were prepared as reported previously 2 , dried a minimum of two times as solutions in benzene-d 6 (substrates 3, 5, 11) or toluene-d 8 (substrates 7, 9) over freshly activated Davison 4A molecular sieves, and degassed by freeze -pump -thaw methods. They were then stored in vacuum-tight storage flasks. Solutions of 9 were protected from light to minimize non-catalytic endocyclization reactions. The organolanthanide precatalysts Ln[CH(SiMe 3 ) 2 ] 3 (Ln = La, Nd, Sm, Y, Lu), 3 and Ln[N(SiMe 3 ) 2 ] 3 4 (Ln = La, Nd, Sm, Y) were prepared by published procedures.

Neutral Group‐IV Metal Catalysts for the Intramolecular Hydroamination of Alkenes

“…Corresponding second-order dependences on the substrate concentration have only been reported for selected examples of rare-earth-metal-catalyzed intramolecular hydroamination [9] and hydrophosphination reactions. [10] On the other hand, comparable kinetic studies performed with two ansaZr catalysts suggested a zero-order dependence on the substrate concentration.…”

“…However, second-order dependences on the substrate concentration have been described for selected examples of rare-earthmetal-catalyzed intramolecular hydroamination [9] and hydrophosphination reactions. [10] Although the results obtained for the formation of piperidines catalyzed by Ti(NMe 2 ) 4 , Ind 2 TiMe 2 , Ind 2 ZrMe 2 and Ind 2 HfMe 2 suggest that for these reactions Ti catalysts show increased catalytic activity compared with the corresponding Zr catalysts, the formation of aminocyclopentane side-products by C-H activation processes was found to be a severe drawback of the Ti catalysts. Fortunately, these side-products are not formed in Ind 2 ZrMe 2 -and Ind 2 HfMe 2 -catalyzed reactions.…”

Homolysis of the Ln–N bond: Synthesis, characterization and catalytic activity of organolanthanide(II) complexes with furfuryl- and tetrahydrofurfuryl-functionalized indenyl ligands

“…GC-MS analyses were carried out on an Agilent 6890/Micromass GCT-MS instrument. 1 H NMR and 13 C NMR spectra for analyses of compounds were recorded on a Bruker DPX-300 NMR spectrometer in pyridine-d 5 for lanthanide complexes and in CDCl 3 for organic compounds and polymers, and chemical shifts for 1 H and 13 C NMR spectra were referenced to internal solvent resonances. Gel permeation chromatography (GPC) analyses of polymer samples were carried at 30°C using THF as an eluent on a Waters-150C instrument and calibrated using monodispersed polystyrene standards at a flow rate of 1.0 mL min À1 .…”

Phosphines and Related Tervalent Phosphorus Systems

“…238 Further studies have been reported of the intramolecular hydrophosphination/cyclisation of primary phosphino-alkynes and -alkenes to form cyclic phosphines in the presence of organolanthanide complexes. 239 Diphenylphosphine has been shown to add diastereoselectively to benzaldimines coordinated to a chromium tricarbonyl acceptor, to form complexed chiral aminoalkylphosphines. 240 The synthesis of P-chiral functionalised secondary phosphines by addition of iron-complexed primary phosphines to alkenes and alkynes has been reviewed.…”