Alcohol amination with ammonia catalyzed by an acridine-based ruthenium pincer complex: a mechanistic study.

The mechanistic course of the amination of alcohols with ammonia catalyzed by a structurally modified congener of Milstein's well-defined acridine-based PNP-pincer Ru complex has been investigated both experimentally and by DFT calculations. Several key Ru intermediates have been isolated and characterized. The detailed analysis of a series of possible catalytic pathways (e.g., with and without metal-ligand cooperation, inner- and outer-sphere mechanisms) leads us to conclude that the most favorable pathway for this catalyst does not require metal-ligand cooperation.

Selective alkylation of amines with alcohols by Cp*-iridium(III) half-sandwich complexes.

[Cp*Ir(Pro)Cl] (Pro = prolinato) was identified among a series of Cp*-iridium half-sandwich complexes as a highly reactive and selective catalyst for the alkylation of amines with alcohols. It is active under mild conditions in either toluene or water without the need for base or other additives, tolerates a wide range of alcohols and amines, and gives secondary amines in good to excellent isolated yields.

Chemical surface modification of self-assembled monolayers by radical nitroxide exchange reactions.

This article describes the application of nitroxide exchange reactions of surface-bound alkoxyamines as a tool for reversible chemical modification of self-assembled monolayers (SAMs). This approach is based on radical chemistry, which allows for introduction of various functional groups and can be used to reversibly introduce functionalities at surfaces. To investigate the scope of this surface chemistry, alkoxyamines with different functionalities were synthesized and were then applied to the immobilization of, for example, dyes, sugars, or biotin. Surface analysis was carried out by contact angle, X-ray photoelectron spectroscopy, and fluorescence microscopy measurements. The results show that this reaction is highly efficient, reversible, and mild and allows for immobilization of various sensitive functional groups. In addition, Langmuir-Blodgett lithography was used to generate structured SAMs. Site-selective immobilization of a fluorescent dye could be achieved by nitroxide exchange reactions.

Diastereoselective intramolecular Friedel-Crafts alkylation of tetralins.

An efficient and versatile synthesis of cis-hexahydrobenzophenanthridines starting from readily available tetralins has been developed using an intramolecular Friedel-Crafts alkylation as a key step. The substrates were prepared via a highly stereocontrolled rhodium-catalyzed ring-opening reaction of meso-oxabicyclic alkenes and a hydrogenation sequence. Thus, a wide variety of complex tetracyclic compounds have been isolated with a high level of regio-, diastereo-, and enantioselectivity.

Patterning of functional compounds by multicomponent Langmuir-Blodgett transfer and subsequent chemical modification.

The multicomponent transfer of functional molecules by Langmuir-Blodgett (LB) technique onto solid substrates offers an interesting route for generation of functionalized patterns by self-assembly over large surface areas. In the present paper, we discuss LB transfer of mixed LB films containing different functional amphiphiles (an azide, an estrone derivate, a lithocholic acid derivative, or an alkoxyamine) in combination with dipalmitoylphosphatidyl choline (DPPC). The effect of the mixing ratio on pattern formation is discussed, and we provide some general design rules for the synthesis of functional molecules to be applicable for the multicomponent LB transfer process. We show that these functional compounds can be successfully transferred to oxidized Si wafers in stripe pattern. Covalent attachment of the functional entities is easily achieved, and the patterned surfaces are then ready for further chemical manipulation. This is demonstrated by site-specifically covalent attaching dye molecules applying the copper(l)-catalyzed alkyne azide click reaction (CuAAC), the thiol-ene reaction, and a surface-initiated radical polymerization.

Polymer brushes by nitroxide-mediated polymerization.

This review article describes the preparation of polymer brushes by nitroxide-mediated radical polymerization using either the 'grafting to' or the 'grafting from' approach. The use of TEMPO as a classical initiator is intensively described. More sophisticated nitroxides are also included in the discussion. Brush formation on flat surfaces such as wafers and also on particles is reported. Finally, some applications of polymer brushes are presented.