Stereochemistry of Palladium-Mediated Synthesis of PAMP−BH₃:  Retention of Configuration at P in Formation of Pd−P and P−C Bonds

Abstract

Treatment of Pd((S,S)-Chiraphos)(o-An)(I) (3, o-An = o-MeOC6H4) with either enantiomer of highly enantioenriched PH(Me)(Ph)(BH3) (1) gave the phosphido-borane complex Pd((S,S)-Chiraphos)(o-An)(P(Me)(Ph)(BH3)) (4) with retention of configuration at phosphorus, as shown by X-ray crystal structure determinations for both diastereomers of 4. Heating either diastereomer of 4 with diphenylacetylene gave Pd((S,S)-Chiraphos)(PhCCPh) (5) and P(o-An)(Me)(Ph)(BH3) (2) with retention of configuration at phosphorus.

Metal-Catalyzed Asymmetric Synthesis of P-Stereogenic Phosphines

“…29 Switching the ligand to Chiraphos, however, allowed them to separate and isolate both diastereomers of the phosphido-borane intermediate 24 and to demonstrate that the formation of both palladium-phosphorus and phosphorus-carbon bonds proceeded with retention of configuration at phosphorus, as expected. 30 Moreover, the hypothesis of Scheme 12, that enantiomers (R P )-23 and Thus, these studies provided proof of the concept shown in Scheme 12, as well as fundamental stereochemical information. The enantioselectivity in the catalysis might be improved in future work 31 by increasing the steric discrimination between the P-substituents, the successful strategy of Scheme 3.…”

Recent Advances in Metal-Catalyzed C–P Bond Formation

“…Slowing reductive elimination with a Pd-C 6 F 5 group enabled isolation and separation of the diastereomers of an analog of the key intermediate (Scheme 56) [94]. The stereochemical details of Pd-P bond formation and P-C reductive elimination, which both proceed with retention at phosphorus, had been elucidated earlier in related Pd(Chiraphos) complexes [95,96].…”

Synthesis and reactivity of imidazole-1-sulfonate esters (imidazylates) in substitution, elimination, and metal-catalyzed cross-coupling reactions: a review

“…[ is the most commonly used method for construction of C(sp 2 )-P bonds. [93][94][95][96][97][98][99] The P-arylation of H-phosphonate diesters 106 with aryl imidazylates 105 to form arylphosphonates 108 was reported in 2009. The reaction was performed in the presence of i PrNEt, 1,4-dioxane and catalytic amounts of Pd(OAc) 2 and 1,3-bis(diphenylphosphino)propane(DPPP) 107.…”