Yong‐Qiang Zhang

Hydroxy‐Directed, Fluoride‐Catalyzed Epoxide Hydrosilylation for the Synthesis of 1,4‐Diols

A novel highly regioselective, fluoride-catalyzed hydrosilylation of β-hydroxy epoxides has been developed. The reaction is modular and applicable to the synthesis of a broad range of 1,4-diols. Fluoride is crucial for two reasons: First, it promotes the formation of a silyl ether (which contains a Si-H bond) and, second, it enables ring opening by an intramolecular S(N)2 reaction through activation of the silane. The reaction can be performed under air.

Amide‐Substituted Titanocenes in Hydrogen‐Atom Transfer Catalysis

Two new catalytic systems for hydrogen-atom transfer (HAT) catalysis involving the N-H bonds of titanocene(III) complexes with pendant amide ligands are reported. In a monometallic system, a bifunctional catalyst for radical generation and reduction through HAT catalysis depending on the coordination of the amide ligand is employed. The pendant amide ligand is used to activate Crabtrees catalyst to yield an efficient bimetallic system for radical generation and HAT catalysis.

Titanocene-Catalyzed Radical Opening of N-Acylated Aziridines

Aziridines activated by N-acylation are opened to the higher substituted radical through electron transfer from titanocene(III) complexes in a novel catalytic reaction. This reaction is applicable in conjugate additions, reductions, and cyclizations and suited for the construction of quaternary carbon centers. The concerted mechanism of the ring opening is indicated by DFT calculations.

SN2 Reactions at Tertiary Carbon Centers in Epoxides

Described herein is a novel concept for SN 2 reactions at tertiary carbon centers in epoxides without activation of the leaving group. Quantum chemical calculations show why SN 2 reactions at tertiary carbon centers are proceeding in these systems. The reaction allows flexible synthesis of 1,3-diol building blocks for natural product synthesis with excellent control of the relative and absolute configurations.

Synthesis of 1,3‐Amino Alcohols by Hydroxy‐Directed Aziridination and Aziridine Hydrosilylation

We describe an approach to N-tosyl 1,3-amino alcohols that consists of a diastereoselective aziridination reaction of acyclic allylic alcohols and an unprecedented regioselective hydrosilylation of α-hydroxy aziridines. The products contain up to three contiguous stereocenters. Computational studies outline key aspects of the aziridination mechanism, which is different and more intricate than anticipated.