Trans Effect of Different Coordinated Atoms of Planar Chiral Ferrocene Ligands with the Same Backbone in Palladium−Catalyzed Allylic Substitutions

Abstract

A series of planar chiral P,S-, P,(CdN)-, and S,(CdN)-bidentate ferrocenyl ligands 4, 5, 8, and 9 with the same central and planar chiralities were prepared from the commercially available starting material N,N-dimethyl-(S)-R-ferrocenylethylamine. A Pd-catalyzed asymmetric allylic alkylation reaction was used as a model reaction to study the trans effect of the coordination atoms by these ligands. On the basis of the reaction results and the study of X-ray diffraction as well as 1 H and 13 C NMR spectra of the complexes (12-15), the sequence of the trans effect was established as CdN > P > S, which was supported by molecular modeling at the PM3 level.

Ferrocene-derived P,N ligands: synthesis and application in enantioselective catalysis

“…This can be attributed to the higher trans-effect of the phosphorus, as compared to the nitrogen, resulting in an electronic differentiation of the two allylic termini in the transition state complex. It has been shown that the attack of the nucleophile happens at the allylic terminus trans to phosphorus [51,52]. It is beyond the scope of this review to cover all chiral hybrid P,N ferrocene ligands used in enantioselective allylic substitutions.…”

Preparation of S-Containing Aminophosphine and Phosphoramidite Ligands and Their Applications in Enantioselective C–C Bond Forming Reactions

“…These results indicated that the enantioselectivity of Pd-catalyzed asymmetric allylic substitution could be affected by the coordinating atoms. The heterodonor ligands equipped with weak and strong donor heteroatom pairs gave rise to different electronic properties, and could finetune the activity and enantioselectivity of asymmetric catalytic allylic alkylation [19]. On the other hand, it seems that the dimension of the groups linked to the coordinating atoms could also affect their enantioselectivity.…”

“…Hiroi et al studied the synthesis of (s)-proline-derived phosphines bearing various organosulfur groups for allylic substitution reactions [13][14][15][16]. Enders et al [17,18], Dai et al [19], Carretero et al [20,21], Manoury et al [22] and Toru et al [23] have applied ferrocene as scaffold and synthesized a series of P/S ligands. These P/S ligands were successfully applied in Pd-catalyzed enantioselective C-C bond forming reactions.…”

1,2‐P,N‐Bidentate Ferrocenyl Ligands

“…To take advantage of the above model reaction, Hou and Dai also established the sequence of the trans-effect is C¼N > P > S for ligands 57 ( Figure 5.6), having the same skeleton and chiralities but different disposition of the coordinated atoms, by analysis of the reaction results, molecular modeling at the PM3 level and study of X-ray diffraction and 1 H, 13 C NMR spectra of the complexes [63]. Different from the reaction of 1,3-diphenylpropenyl acetate, those of cyclic alkenyl acetates have found applications in natural products synthesis [64].…”