131758-40-2Relevant academic research and scientific papers
Stereodivergent SN2@P reactions of borane oxazaphospholidines: Experimental and theoretical studies
Zijlstra, Hester,Leon, Thierry,De Cozar, Abel,Guerra, Celia Fonseca,Byrom, Daniel,Riera, Antoni,Verdaguer, Xavier,Bickelhaupt, F. Matthias
, p. 4483 - 4491 (2013)
The stereodivergent ring-opening of 2-phenyl oxazaphospholidines with alkyl lithium reagents is reported. N-H oxazaphospholidines derived from both (+)-cis-1-amino-2-indanol and (-)-norephedrine provide inversion products in a highly stereoselective process. In contrast, N-Me oxazaphospholidines yield ring-opening products with retention of configuration at the P center, as previously reported by Juge and co-workers. As a result, from a single amino alcohol auxiliary, both enantiomers of key P-stereogenic intermediates could be synthesized. Theoretical studies of ring-opening with model oxazaphospholidines at the DFT level have elucidated the streochemical course of this process. N-H substrates react in a single step via preferential backside SN2@P substitution with inversion at phosphorus. N-methylated substrates react preferentially via a two-step frontside SN2@P, yielding a ring-opened product in which the nucleophilic methyl binds to P with retention of configuration. DFT calculations have shown that the BH3 unit is a potent directing group to which the methyl lithium reagent coordinates via Li in all the reactions studied.
P-chiral, monodentate ferrocenyl phosphines, novel ligands for asymmetric catalysis
Colby, Elizabeth A.,Jamison, Timothy F.
, p. 156 - 166 (2003)
Eight P-chiral monodentate ferrocenyl phosphines (1a-h) were prepared in high enantiomeric excess (>95% ee in most cases) by way of an ephedrine-based oxazaphospholidine borane complex. Primary alkyl, secondary alkyl, and substituted aromatic substituents were successfully introduced at the phosphorus center, along with ferrocenyl and phenyl groups, generating phosphines of the general structure FcP(Ph)(R) (Fc = ferrocenyl, R = aryl, alkyl). The synthetic route employed provides facile access to a previously undeveloped class of chiral monophosphines. These compounds were evaluated as ligands in asymmetric catalytic reductive coupling of alkynes and aldehydes and were found to provide the desired chiral allylic alcohols with good regioselectivity and ee in many cases and with complete (E)-selectivity (>98:2) in all cases.
Study of the bonding properties of the new ligands C5H3N(2-R′)(6-CH2PPhR) toward rhodium(I). Evidence for a dynamic competition for bonding between O- and N-donor centers when R = o-Anisyl, R′ = Me
Yang, Hong,Lugan, No?l,Mathieu, René
, p. 2089 - 2095 (2008/10/08)
The bonding properties of the optically active chiral-at-P polydentate ligands C5H3N(2-R′)(6-CH2PPhR) (R = Me, R′ = H, Me; R = o-anisyl, R′ = H, Me) and the achiral ligand C5H3N(2-Me)(6-CH2PPh2) toward (COD)Rh+ are reported. The results show that steric hindrance of the 2-position of the pyridyl ring induces a labile character of the Rh-N bond. Moreover, for R = o-anisyl and R' = Me, a dynamic competition for bonding between the N-and O-donating centers is observed. Comparison of the solid state structures of complexes [Rh(COD)(C5H4N(2-CH2PPhMe)][BF4] and [Rh(COD)(C5H3N(2-Me)(6-CH2PPh 2)][BF4] shows a significant bond lengthening of the Rh-N bond in the latter complex, consistent with its fluxional behavior observed in solution.
Synthesis and reactions of phosphine-boranes. Synthesis of new bidentate ligands with homochiral phosphine centers via optically pure phosphine-boranes
Imamoto, Tsuneo,Oshiki, Toshiyuki,Onozawa, Takashi,Kusumoto, Tetsuo,Sato, Kazuhiko
, p. 5244 - 5252 (2007/10/02)
Secondary and tertiary phosphine-boranes were synthesized in one-pot from phosphine oxides or substituted chlorophosphines without isolation of the intermediate phosphines. Phosphine-boranes having a methyl group were metalated with sec-butyllithium. The generated carbanions reacted with alkyl halides or carbonyl compounds to yield various phosphine-borane derivatives. The carbanions underwent copper(II)-promoted oxidative coupling without impairment of the borane functionality. Secondary phosphine-boranes reacted with alkyl halides, aldehydes, or α,β-unsaturated carbonyl compounds to give phosphine-borane derivatives having a functional group. The boranato group of phosphine-boranes was removed in a stereospecific manner with retention of configuration by treatment with a large excess of amine such as morpholine. A new route to bidentate ligands with homochiral phosphine centers has been explored by utilizing these characteristic reactivities of phosphine-boranes. Thus, optically pure (S,S)-1,2-bis(o-anisylphenylphosphino)ethane, (R,R)-1,2-bis(tert-butylphenyl-phosphino)ethane, and (S,S)-1,4-bis(o-anisylphenylphosphino)butane have been synthesized via phosphine-boranes.
