Pd(II)-Catalyzed Asymmetric [2+2] Annulation for the Construction of Chiral Benzocyclobutenes.

Asymmetric de novo synthesis of benzocyclobutenes (BCBs) via catalytic intermolecular reaction is highly desired for efficient access to this important class of compounds, yet such a strategy remains unmet challenge. Here, we report a Pd/Pyrox-catalyzed asymmetric [2+2] annulation between arylboronic acids and functionalized alkenes, providing an unprecedented efficient protocol to access various enantio-enriched BCBs in a modular and versatile manner under mild conditions. A broad substrate scope with excellent enantioselectivity has been achieved under the current protocol.

Site-Selective Modification of α-Amino Acids and Oligopeptides via Native Amine-Directed γ-C(sp)-H Arylation.

Site-selective modification of chemically and biologically valuable α-amino acids and peptides is of great importance for biochemical study and pharmaceutical development. Few methods based on remote C(sp)-H functionalization of aliphatic side-chains of peptides has been disclosed in recent years. In this report, we developed a novel approach for γ-C(sp)-H and γ-/δ-C(sp)-H arylation of α-amino acids with α-hydrogen by native amine-directed C-H functionalization and further realized the γ-C(sp)-H arylation of -terminally unprotected peptides.

Free Amino Group-Directed γ-C(sp)-H Arylation of α-Amino Esters with Diaryliodonium Triflates by Palladium Catalysis.

Free amino group-directed C(sp)-H functionalization of aliphatic amines is a fundamental challenge in synthetic organic chemistry. Also, the NH-directed C(sp)-H functionalization of α-amino acids and their derivatives remains barely explored. With palladium as the catalyst and AgO as the additive, we developed the first NH-directed γ-C(sp)-H arylation of α-amino esters with diaryliodonium triflates for the construction of synthetically useful γ-aryl-α-amino esters, and the result of the KIE study suggested that the catalytic reaction involved an irreversible C-H cleavage as the rate-determining step.