Synthesis of P-Stereogenic Phosphinamides via Pd(II)-Catalyzed Enantioselective C-H Alkynylation.

P-Stereogenic phosphinamides represent important structural elements in chiral organocatalysts and bioactive compounds. Herein, we report Pd(II)-catalyzed enantioselective C-H alkynylation using cheap commercially available l-pyroglutamic acid as a chiral ligand. A range of structurally diverse P-stereogenic phosphinamides was prepared in good yields with high enantioselectivities via desymmetrization and kinetic resolution. A tailor-made congested directing group, N-ethyl-N-(3-methylpyridin-2-yl)amino, was crucial for the reactivity.

Synthesis of Chiral Sulfoxides via Pd(II)-Catalyzed Enantioselective C-H Alkynylation/Kinetic Resolution of 2-(Arylsulfinyl)pyridines.

A Pd(II)-catalyzed enantioselective C-H alkynylation of 2-(arylsulfinyl)pyridines via kinetic resolution using cheap and commercially available l-pGlu-OH as a chiral ligand is reported. A wide range of 2-(arylsulfinyl)pyridines were compatible with this protocol, giving the alkynylation products and recovered sulfoxides in high yields with high enantioselectivities (up to 99% ee). Furthermore, the enantioenriched products can be easily transformed to several other types of chiral sulfoxide scaffolds with the retention of enantiopurity.

Pd(II)-Catalyzed enantioselective arylation of unbiased methylene C(sp3)-H bonds enabled by a 3,3'-F2-BINOL ligand.

Palladium-catalyzed asymmetric functionalization of unbiased methylene C(sp3)-H bonds is a long-standing challenge. Here, we report a Pd(ii)-catalyzed highly enantioselective arylation of unbiased methylene C(sp3)-H bonds enabled by a strongly coordinating bidentate 2-pyridinylisopropyl (PIP) directing group and an easily accessible 3,3'-F2-BINOL chiral ligand. The use of aryl iodides with the combination of 3,3'-F2-BINOL was beneficial for high enantiocontrol. A range of aliphatic amides and aryl iodides were tolerated, providing the desired arylated products in high enantioselectivities (up to 96% ee). The PIP directing group could be removed under mild conditions without erosion of enantiopurity.

Pd(II)-Catalyzed Enantioselective Intramolecular Arylation of Unbiased C(sp3)-H Bonds to Construct Chiral Benzo-ring Compounds.

The asymmetric synthesis of chiral benzo-ring containing compounds through enantioselective intramolecular arylation of unbiased methylene C(sp3)-H bonds was reported. Judicious choice of non-C2-symmetric chiral phosphoric acid (CPA) ligand is crucial for the high reactivity and enantioselectivity. The slight decrease in enantioselectivity at the late stage of the reaction was attributed to the hydrolysis of CPA ligands to the corresponding BINOL.

Late-stage functionalization of peptides via a palladium-catalyzed C(sp3)-H activation strategy.

Peptides hold great promise in proteomics, diagnostics and drug discovery. While natural peptides continue to be of key importance, chemically modified unnatural peptides have been found to show enhanced biological activities and improved therapeutic capabilities compared to their natural counterparts. Therefore, the development of efficient and versatile strategies to enable easy access to unnatural peptides is in high demand. In recent years, palladium-catalyzed direct functionalization of inert C(sp3)-H bonds has emerged as a powerful and straightforward synthetic strategy for late-stage modification of peptides. In this review, we summarize recent progress in this emerging field. For clarity, this review is organized into three sections according to the functionalization of the peptide side-chains at ß-, γ-, and δ-positions.

Scalable Formal Synthesis of (-)-Quinocarcin.

A scalable and unified strategy is described for the synthesis of (-)-quinocarcin, an important tetrahydroisoquinoline antitumor alkaloid. The strategy allows the practical formal synthesis of (-)-quinocarcin in 13 steps and 4.8% overall yield using N-phthaloyl-l-alanine as a chiral pool. It features the gram-scale and stereoselective synthesis of the tetrahydroisoquinoline moiety (AB ring) via Pd-catalyzed C(sp3)-H arylation and Pictet-Spengler condensation and a Cu(I)-catalyzed exo-selective [C + NC + CC] coupling reaction to generate the chiral pyrrolidine motif (D ring).