Synthesis of a tetrasubstituted tetrahydronaphthalene scaffold for α-helix mimicry via a MgBr2-catalyzed Friedel-Crafts epoxide cycloalkylation.

α-Helices are ubiquitous protein recognition elements that bind diverse biomolecular targets. The synthesis of a small molecule scaffold to present the side chains of an α-helix is described. The 1,3,5,7-tetrasubstituted 1,2,3,4-tetrahydronaphthalene scaffold, providing mimicry of the i, i+3, and i+4 positions of an α-helix, was synthesized using a novel MgBr2-catalyzed Friedel-Crafts epoxide cycloalkylation as the key step.

Ruthenium-catalyzed asymmetric epoxidation of olefins using H2O2, part I: synthesis of new chiral N,N,N-tridentate pybox and pyboxazine ligands and their ruthenium complexes.

The synthesis of chiral tridentate N,N,N-pyridine-2,6-bisoxazolines 3 (pybox ligands) and N,N,N-pyridine-2,6-bisoxazines 4 (pyboxazine ligands) is described in detail. These novel ligands constitute a useful toolbox for the application in asymmetric catalysis. Compounds 3 and 4 are conveniently prepared by cyclization of enantiomerically pure alpha- or beta-amino alcohols with dimethyl pyridine-2,6-dicarboximidate.

Ruthenium-catalyzed asymmetric epoxidation of olefins using H2O2, part II: catalytic activities and mechanism.

Asymmetric epoxidation of olefins with 30 % H2O2 in the presence of [Ru(pybox)(pydic)] 1 and [Ru(pyboxazine)(pydic)] 2 has been studied in detail (pybox = pyridine-2,6-bisoxazoline, pyboxazine = pyridine-2,6-bisoxazine, pydic = 2,6-pyridinedicarboxylate). 35 Ruthenium complexes with sterically and electronically different substituents have been tested in environmentally benign epoxidation reactions. Mono-, 1,1-di-, cis- and trans-1,2-di-, tri-, and tetra-substituted aromatic olefins with versatile functional groups can be epoxidized with this type of catalyst in good to excellent yields (up to 100 %) with moderate to good enantioselectivies (up to 84 % ee).

Synthesis of a new chiral N,N,N-tridentate pyridinebisimidazoline ligand library and its application in Ru-catalyzed asymmetric epoxidation.

A small ligand library of chiral tridentate N,N,N-pyridinebisimidazolines have been synthesized for the first time. This new class of ligands can be easily tuned and synthesized on multi g-scale. The usefulness of the ligands is shown in the ruthenium-catalyzed asymmetric epoxidation with hydrogen peroxide as oxidant.

Convenient method for epoxidation of alkenes using aqueous hydrogen peroxide.

[reaction: see text] The complex [Ru(tpy)(pydic)] (1a) is an active catalyst for epoxidation of alkenes by aqueous 30% hydrogen peroxide in tertiary alcohols. The protocol is simple to operate and gives the corresponding epoxides in good to excellent yields. Chiral enantiopure [Ru(tpy)(pydic)] complexes have been synthesized and successfully applied in this procedure.