Martin Wills

Chemistry and clinical biology of the bryostatins.

Bryostatins are a class of antineoplastic compounds isolated from the bryozoans Bugula neritina. A wide range of scientific research is currently underway, studying different aspects of the bryostatins. In this review we try to summarize the latest findings, including all the topics involved, from marine biology to medicinal chemistry.

Enantioselective catalysis using phosphorus-donor ligands containing two or three P–N or P–O bonds

This review describes some recent developments in the area of asymmetric catalysis using organometallic complexes of ligands which contain two or three P-O or P-N bonds. This category of ligands has, until the last five years or so, been underrepresented in asymmetric catalysis, particularly in contrast to phosphine ligands. Recent breakthroughs in methodology for the synthesis and manipulation of such materials have resulted in the delivery of ligands which demonstrate remarkably high enantioinduction properties in a series of asymmetric transformations.

Asymmetric catalysis using iron complexes – ‘Ruthenium Lite’?

A review of recent developments in the use of iron catalysts for asymmetric transformations, including hydrogenations, transfer hydrogenation, hydrosilylation and oxidation reactions.

Ru(II) complexes of N-Alkylated TsDPEN ligands in asymmetric transfer hydrogenation of ketones and imines

N-Alkylated TsDPEN derivatives bearing a small alkyl group act as highly efficient ligands in Ru(II) complexes for the asymmetric transfer hydrogenation of imines and ketones. A larger alkyl group serves to significantly reduce the activity of the catalyst; however, high enantiomeric excesses are still obtained. An X-ray crystal structure of the N-benzyl derivative reveals a conformation that permits hydrogen transfer through a six-membered transition state. A transition state structure for the imine reduction process is proposed.

Application of ruthenium complexes of triazole-containing tridentate ligands to asymmetric transfer hydrogenation of ketones

The synthesis of a series of tridentate ligands based on a homochiral 1,2-diamine structure attached to a triazole group and their subsequent applications to the asymmetric transfer hydrogenation of ketones are described. In the best cases, alcohols of up to 93% ee were obtained. Although base is not required, the use of Ru(3)(CO)(12) as metal source is essential, indicating a unique mechanism for the formation of the active catalyst.

Rhodium versus ruthenium: contrasting behaviour in the asymmetric transfer hydrogenation of α-substituted acetophenones

Abstract The reduction of a number of α-substituted acetophenones has been achieved using both ruthenium(II)- and rhodium(III)-based asymmetric transfer hydrogenation catalysts employing formic acid as the hydrogen donor.

The importance of the N–H bond in Ru/TsDPEN complexes for asymmetric transfer hydrogenation of ketones and imines

Ru(II) complexes of TsDPEN containing two alkyl groups on the non-tosylated nitrogen atom are poor catalysts for asymmetric transfer hydrogenation of ketones and imines; this observation provides direct evidence for the importance of the N-H interaction in the transition state for ketone reduction.

A Continuous-Flow Method for the Generation of Hydrogen from Formic Acid

A continuous-flow method for generation of hydrogen from the ruthenium-catalyzed decomposition of formic acid in the presence of a base is described. The rate of addition of formic acid to the reactor is controlled by a temperature feedback mechanism or by an impedance-based feedback system.

Ether-tethered Ru(II)/TsDPEN complexes; synthesis and applications to asymmetric transfer hydrogenation

A new type of Ru(II)/TsDPEN catalyst containing an ether-based linking tether has been prepared and shown to exhibit excellent activity in asymmetric transfer hydrogenation reactions of ketones. Related complexes containing a hydroxyl-terminated alkyl chain have also been prepared and tested as asymmetric catalysts. In some cases the activity of the new catalyst type complements that of the closely related alkyl-chain tethered complexes.

An Unexpected Directing Effect in the Asymmetric Transfer Hydrogenation of α,α-Disubstituted Ketones

α,α-Disubstituted ketones containing an aromatic ring or alkene are reduced in high enantiomeric excess using an asymmetric transfer hydrogenation catalyst. The sense of reduction indicates that the unsaturated region of the ketone adopts a position adjacent to the Ru-bound η(6)-arene ring in the reduction transition state.