Other acronyms used for these ligands include FOXAP, FcPHOX and DIPOF. First reported by Richards and Uemura, the synthesis of these ligands was improved by utilisation of the highly diastereoselective lithiation conditions reported by Sammakia. The following lists reactions, organised by metal (Pd Ru Ir Cu Ag Ni), for which the application of these ligands has resulted in >80% ee. ACE = Asymmetric Catalytic Efficiency. Literature covered until end 2017 (60 entries – including [Phosferrox-Ru].
Pd – Allylic amination OBC13-11-7412.
GC02-4-103. This reaction with (S,Sp)-PN-L1a in ionic liquid [bmim][PF6] (up to 86% ee)
Pd – Intramolecular arylation JACS17-139-16486
Pd – Diazabicycle desymmetrisation JACS17-139-17787
Pd – 3 + 2 cycloaddition ACSCat16-6-6408
One example where the t-Bu quinone substituents are replaced by i-Pr substituents but this resulted in a signifcant reduction in ee (to 74% with R = Ph).
Ru – Transfer hydrogenation OL97-62-6104
Similar results from in situ generated catalyst also reported in JOMC99-572-163. This paper also describes the preparation of [(S,Sp)-PN-L1a]RuCl2(PPh3). An octahedral adduct derived from this, [(S,Sp)-PN-L1a]RuCl2P(OMe3)2, has also been applied to transfer hydrogenation (94% ee, 96% conversion from PhCOMe, ACE = 71.8), see: JOMC08-693-2535.
Ir – Hydrogenation ASC04-346-909
TA07-18-629 The catalyst in this example is the isolated adduct derived from (S,Sp)-PN-L1b, [Ir(COD)Cl]2 and NaBArF.
Ir – Hydrosilylation Orgmet99-18-2271
Cu – Conjugate addition Tet97-53-16503
With the 3,5-(CF3)2C6H3 analogue of (S,Sp)-PN-L1a 8 : 1 anti : syn diastereoselectivity resulted.
Lower anti:syn selectivity with R1 = o-Ar, t-Bu and CH2OBn. High syn selectivity with all R1 substituents achieved using a 2,3-dihydroimidazo[1,2-a]pyridine-OH (i.e. an N,O-ligand) under the same conditions at RT.
Anti selectivity [(4R, 1’S) using (S,Sp)-PN-L1a] changes to syn (>15: 1)selectivity (4R, 1’R) where the Ph groups of (S,Sp)-PN-L1a are replaced by (3,5-CF3)2C6H3 groups.
Addition of water* is required to suppress pyrrolidine formation as a result of 5-endo-trig cyclisation (!) of the enolate resulting from conjugate addition on the carbon of the diphenylimine moiety (the chemoselectivity refered to above). [*The addition of water is not included in the method given in the SI.]
Cu – Conjugate addition-elimination OL09-11-2073
Cu – Mannich reaction JACS08-130-14362
Higher anti selectivity with 4-MeOC6H4 analogue of (S,Sp)-PN-L1a. Reaction syn selective with the 3,5-(CF3)2C6H3 analogue of (S,Sp)-PN-L1a. In both cases ees generally >96%.
Cu – 3 + 2 cycloaddition Angew06-45-1979
With the 3,5-(CF3)2C6H3 analogue of (S,Sp)-PN-L1a these reactions are endo selective.
Reaction further exemplified with the (R,R,Rp)-phosferrox ligand derived from (R,R)-2-amino-1,2-diphenylethanol.
One example with (S,Sp)-PN-L1a from a scoping study in which a Ming-Phos ligand gave a similar result (94% ee, 91% conversion, 15 : 1 dr at -40 oC). Further reaction optimisation and exemplification was with a Ming-phos ligand.
Cu – 4 + 2 cycloaddition Angew14-53-4680
Cu – 3 + 3 cycloaddition Angew13-52-12377
Cu – 3 + 4 cycloaddition ASC16-358-3748
Cu – 3 + 6 cycloaddition OL15-17-1365
With N-methyl-1-[2-(diphenylphosphino)ferrocenyl]ethylamine >20:1 exo:endo was achieved (ee >95%).
Cu(Pd) – Allylation of α–amino acid derivatives Angew17-56-12312
Also applied to the double allylation of a glycine derived aldime ester.
Cu – Beta (1,4) borylation OL14-16-1426
Cu – Sulfonylindole substitution (via in situ vinylogous imine) OL10-12-1688
High anti selectivity and ee achieved with a complex obtained from AgCl/phosphoramidite.
Ag – 3 + 2 cycloaddition OL05-7-5055
With the p-CF3C6H4 (instead of Ph) and benzyl (instead of i-Pr/t-Bu) analogue of (S,Sp)-PN-L1a/b these reaction result in >93% ee with a variety of aryl substituents (i.e. instead of p-ClC6H4).
The description of the catalyst loading and reactions conditions employed differ in the manuscript and SI. SI conditions used in the above scheme. High exo selectivity (>20:1) and ee (82-93%) achieved with a phosphoramidite ligand (this S,R,R ligand will result in the enantiomeric series of products).
Ni – Allylic alkylation Perkin100-2725
Ni – 2 + 2 + 2 cycloaddition JACS10-132-15836
Ni – Denitrogenative annulation JACS10-132-54
Absolute configuration not stated, but may be tentatively assigned as R by comparison to JACS10-132-15836.
Ni – Decarbonylative annulation OL11-13-1374
Absolute configuration not stated, but in all cases may be tentatively assigned as R by comparison to JACS10-132-15836.
Ni – Intramolecular alkene arylcyanation Synlett10-1709
Specific example JACS08-130-12874
Ni – Diazabicycle desymmetrisation JACS17-139-15656
Intermediate in the synthesis of (+)-pancratistatin