Ben L. Feringa

Asymmetric catalysis with transition‐metal complexes is the basis for a vast array of stereoselective transformations and has changed the face of modern synthetic chemistry. Key to this success has been the design of chiral ligands to control the regio‐, diastereo‐, and enantioselectivity. Phosphoramidites have emerged as a highly versatile and readily accessible class of chiral ligands. Their modular structure enables the formation of ligand libraries and easy fine‐tuning for a specific catalytic reaction. Phosphoramidites frequently show exceptional levels of stereocontrol, and their monodentate nature is essential in combinatorial catalysis, where a ligand‐mixture approach is used. In this Review, recent developments in asymmetric catalysis with phosphoramidites used as ligands are discussed, with a focus on the formation of carbon–carbon and carbon–heteroatom bonds.

With the long-term goal of producing nanometer-scale machines, we describe here the unidirectional rotary motion of a synthetic molecular structure fueled by chemical conversions. The basis of the rotation is the movement of a phenyl rotor relative to a naphthyl stator about a single bond axle. The sense of rotation is governed by the choice of chemical reagents that power the motor through four chemically distinct stations. Within the stations, the rotor is held in place by structural features that limit the extent of the rotor's Brownian motion relative to the stator.

The first catalytic asymmetric procedure capable of preparing all 4 diastereoisomers (ee > 99%, de > 98%) of a versatile saturated isoprenoid building block was developed and the value of this new method was demonstrated in its application to the concise total synthesis of two pheromones.

Optically active vinyl triflates are obtained and employed in a series of one pot metal-catalyzed tandem asymmetric transformations.

Highly enantioselective Cu-catalysed 1,4-addition of diphenylzinc to cyclohexenone has been achieved for the first time using a monodentate phosphoramidite ligand.

A library of 96 unique monodentate phosphoramidite ligands has been synthesized in solution and used in the asymmetric conjugate addition of potassium vinyltrifluoroborate to enones resulting in up to 88% ee.

It is no longer necessary to use dialkylzinc reagents to obtain enantioselectivities >95% in the copper-catalyzed asymmetric conjugate addition of organometallic compounds to cyclic enones. We now report how this can be accomplished by using inexpensive and readily available Grignard reagents. Screening of bidentate ligands provided outstanding results with copper complexes of commercially available chiral ferrocenyl-based diphosphines, in particular TaniaPhos and JosiPhos derivatives. These catalysts tolerate a range of Grignard reagents and different cyclic enones as substrates, leading to high regioselectivities and unprecedented enantioselectivities. Moreover, the reactions are successful with moderate catalyst loading (5 mol %) under mild conditions and in the absence of additives.

A new class of functional models for non‐heme iron‐based dioxygenases, including [(N3Py‐Me)Fe(CH₃CN)₂](ClO₄)₂ and [(N3Py‐Bn)Fe(CH₃CN)₂](ClO₄)₂ {N3Py‐Me = [di(2‐pyridyl)methyl]methyl(2‐pyridyl)methylamine; N3Py‐Bn = [di(2‐pyridyl)methyl]benzyl(2‐pyridyl)methylamine}, is presented here. NMR, UV and X‐ray analyses revealed that six‐coordinate low‐spin Fe^II complexes with the pyridine N‐atoms and the tertiary amine functionality of the ligand bound to Fe are formed. The two remaining coordination sites located cis to each other are occupied by labile CH₃CN groups that are easily exchanged by other ligands. We demonstrate that the reactivity and stereoselectivity of the complexes investigated depend on the choice of the solvent. The complexes have been examined as catalysts for the oxidation of both alkanes and olefins in CH₃CN. In this solvent alkanes are oxidized to alcohols and ketones and olefins to the corresponding cis‐epoxides and cis‐diols. In acetone as solvent a different reactivity pattern was found, with, as the most striking example, the trans‐dihydroxylation of cis‐olefins. ¹⁸O‐labeling studies in CH₃CN establish incorporation of ¹⁸O from H₂¹⁸O₂ and H₂¹⁸O in both the epoxide and the diol implicating an HO‐Fe^V=¹⁸O active intermediate originating from an H₂¹⁸O‐Fe^IIIOOH species. These results are in full agreement with mechanistic schemes derived for other dioxygenase model systems. Based on labeling studies in acetone an additional oxidation mechanism is proposed for this solvent, in which the solvent acetone is involved. This is the first example of a catalyst that can give cis‐ or trans‐dihydroxylation products, just by changing the solvent. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

The combination of monodentate ligands in the rhodium-catalysed enantioselective hydrogenation enables a new approach when searching for the optimal activity and enantioselectivity in catalysis.