A Unified Approach to Customized Chiral Carbon-Bridged ansa-Metallocenes.

Chiral ansa-metallocenes are privileged catalysts for a range of stereoselective transformations. Their synthesis, however, has remained a tremendous challenge, which has prevented a broad and systematic exploration for applications in synthesis and catalysis. A modular approach to such ansa-metallocenes that enables a facile modification of the ring substitution and the ligand bridge, as well as the introduction of various core metals, is described.

A Titanium(III)-Catalyzed Reductive Umpolung Reaction for the Synthesis of 1,1-Disubstituted Tetrahydroisoquinolines.

A catalytic reductive C1-acylation of 3,4-dihydroisoquinolines is presented that gives direct access to 1,1-disubstituted tetrahydroisoquinolines. The reaction is a titanium(III)-catalyzed reductive umpolung process in which nitriles act as effective acylation agents. The method is highly chemo- and regioselective and is demonstrated in 20 examples.

The cross-selective titanium(III)-catalysed acyloin reaction.

A titanium(III)-catalysed intermolecular reductive coupling of ketones or imines with nitriles is described, which gives direct access to α-hydroxylated and α-aminated ketones. This coupling reaction is cross-selective and a catalytic version of the classical acyloin condensation. A reaction mechanism that is supported by first DFT calculations is discussed.