- Diastereoselective Coordination of P-Stereogenic Secondary Phosphines in Copper(I) Chiral Bis(phosphine) Complexes: Structure, Dynamics, and Generation of Phosphido Complexes
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Diastereoselective coordination of racemic secondary phosphines (PHRR′) to Cu(I) precursors containing chiral bis(phosphines) (diphos*) was explored as a potential route to P-stereogenic phosphido complexes. Reaction of [Cu(NCMe)4][PF6] with chiral bis(phospholanes) gave [Cu(diphos*)2][PF6] (diphos? = (R,R)-Me-DuPhos (1), (R,R)-Et-DuPhos (2), or (R,R)-Me-FerroLANE) (3)) or the mono(chelates) [Cu(diphos*)(NCMe)n][PF6] (diphos? = (R,R)-i-Pr-DuPhos, n = 2 (4); diphos? = (R,R)-Me-FerroLANE, n = 1 (5)). Treatment of [Cu(NCMe)4][PF6] with diphos? and PHMe(Is) (Is = 2,4,6-(i-Pr)3C6H2) gave mixtures of diastereomers of [Cu((R,R)-i-Pr-DuPhos)(PHMe(Is))(NCMe)][PF6] (6) and [Cu((R,R)-Me-FerroLANE)(PHMe(Is))][PF6] (7); two of the three expected isomers of the bis(secondary phosphine) complexes [Cu((R,R)-i-Pr-DuPhos)(PhHP(CH2)nPHPh)][PF6] (n = 2 (8); n = 3 (9)) were formed preferentially in related reactions. Reaction of the halide-bridged dimers [Cu((R,R)-i-Pr-DuPhos)(X)]2 or [Cu((R,R)-Me-FerroLANE)(I)]2 with PHMe(Is) gave the labile adducts Cu((R,R)-i-Pr-DuPhos)(PHMe(Is))(X) (X = Cl (10), Br (11), I (12)) and Cu((R,R)-Me-FerroLANE)(PHMe(Is))(I) (13). Complexes 1, 6, and 8-11 were structurally characterized by X-ray crystallography. Variable temperature NMR studies of 6 and 8 showed that the secondary phosphine ligands underwent reversible dissociation. Deprotonation of 6 or 7 generated the P-stereogenic phosphido complexes Cu(diphos*)(PMeIs) (diphos? = (R,R)-i-Pr-DuPhos (14) or (R,R)-Me-FerroLANE) (17)), observed by 31P NMR spectroscopy, but decomposition also occurred. Density functional theory calculations were used to characterize the diastereomers of thermally unstable 17 and the inversion barrier in a model copper-phosphido complex. These observations provided structure-property relationships which may be useful in developing catalytic asymmetric reactions involving secondary phosphines and P-stereogenic copper phosphido intermediates.
- Gibbons, Sarah K.,Valleau, Christopher R. D.,Peltier, Jesse L.,Cain, Matthew F.,Hughes, Russell P.,Glueck, David S.,Golen, James A.,Rheingold, Arnold L.
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- Preparation and use of C2-symmetric bis(phospholanes): Production of α-amino acid derivatives via highly enantioselective hydrogenation reactions
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A new class of chiral C2-symmetric bis(phospholane) ligands has been prepared and used in rhodium-catalyzed asymmetric hydrogenation reactions. We describe a practical, one-pot procedure which utilizes enantiomerically pure 1,4-diol cyclic sulf
- Burk, Mark J.,Feaster, John E.,Nugent, William A.,Harlow, Richard L.
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p. 10125 - 10138
(2007/10/02)
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