Diamidophosphites with remote P∗-stereocentres and their performance in Pd-catalyzed enantioselective reactions

Application of Hydroxyporphyrins-based Phosphite-type Ligands to Asymmetric Pd-Catalyzed Allylic Substitution Reactions

“…These values suggest the anti-orientation of the pseudoequatorial exocyclic substituent at the phosphorus atom and the -(CH 2 ) 3 -part of the pyrrolidine fragment of the phosphabicyclic skeleton and, consequently, the synorientation of the phosphorus lone pair with respect to the C(8) atom (Figure 1). [13,18,[55][56][57][58][59] (S) In order to have an estimation of the steric bulk of ligands 4a-c and 5, we calculated their Tolman cone angles [60] by the reported method using semi-empirical quantum-mechanical AM1 techniques with full optimization of geometrical parameters. [61] The obtained results (Table 1) show that the steric parameters (q) of 4a-c and 5 vary within the interval of 121°-165°, peaking at diamidophosphite 4c.…”

“…In this mechanism, where the nucleophile attacks on the face of the π-allyl system opposite to that of the chirality inducing metal-ligand complex, the generation of asymmetry appears to be relatively challenging. [3,18,53] Both related diamidophosphites 4a and 4b have provided practically equal very good results: enantiomeric quaternary-substituted product (S) (Table 5, entries 2 and 4). Catalysts based on 4c have proved to be less efficient: 83 % conversion and 78 % ee for (S)-10 were achieved in this case.…”

“…Therefore, the development of novel phosphorus-containing stereoselectors is ongoing and still in high demand. [11,[14][15][16][17][18] Chiral phosphite-type compounds constitute a class of prominent ligands because they are favorably distinguished by resistance to oxidation, pronounced π-acidity, and are inexpensive. Also, they can be easily prepared from readily available starting materials via simple condensation processes, including those involving parallel and solidphase synthetic procedures.…”

“…Also, they can be easily prepared from readily available starting materials via simple condensation processes, including those involving parallel and solidphase synthetic procedures. [5,7,11,12,[18][19][20][21][22][23][24][25][26][27][28][29][30][31] In the case of P*-chiral phosphite-type ligands the presence of a stereogenic donor of phosphorus atom significantly promotes successful asymmetric induction in the key step of the catalytic cycle. [2,17,18,32,33] Catalytic systems based on chiral supramolecular ligands with phosphite moiety have recently attracted increasing attention.…”

“…[5,7,11,12,[18][19][20][21][22][23][24][25][26][27][28][29][30][31] In the case of P*-chiral phosphite-type ligands the presence of a stereogenic donor of phosphorus atom significantly promotes successful asymmetric induction in the key step of the catalytic cycle. [2,17,18,32,33] Catalytic systems based on chiral supramolecular ligands with phosphite moiety have recently attracted increasing attention. [34][35][36][37][38] In particular, phosphites and phosphoramidites with BINOL or TADDOL backbone and metalloporphyrin fragment have proven to be highly advantageous building blocks in creating large libraries of supramolecular ligands.…”