Synthesis of α-Aminonitriles via Ammonium-Catalyzed Reactions of Aminoacetonitrile.

α-Aminonitriles are not only broadly useful building blocks but also structural motifs in bioactive molecules. The Strecker reaction is one of the most widely used methods for α-aminonitrile synthesis. However, a severe drawback in Strecker reactions is the required use of a stoichiometric amount of toxic cyanation reagents.

Catalytic Asymmetric Construction of Chiral Amines with Three Nonadjacent Stereocenters via Trifunctional Catalysis.

Pharmaceuticals and biologically active natural products usually contain multiple stereocenters. The development of catalytic asymmetric reactions for the direct construction of complex motifs containing three nonadjacent stereocenters is a particularly important and formidable challenge. In this paper, we report an unprecedented method for the direct asymmetric construction of complex chiral amines with 1,3,5- or 1,3,4-stereocenters from readily available achiral and racemic starting materials.

Catalytic Asymmetric Imine Cross-Coupling Reaction.

Catalytic asymmetric cross-coupling of imines constitutes a particularly desirable method for the synthesis of chiral vicinal diamines directly from readily available achiral precursors. The potential of this method lies in the possibility of utilizing a variety of imines as reacting partners. However, the realization of highly stereoselective cross-coupling of two different imines proved to be a formidable challenge.

Cp*Co(III)-Catalyzed Dearomative [3 + 2] Spiroannulation of 2-Alkenylphenols with Ynamides via C-H Activation.

An oxidative [3 + 2] C-H spiroannulation reaction of 2-alkenylphenols with ynamides has been developed toward the synthesis of spiro[4,5]decane derivatives. This dearomative reaction employs earth-abundant cobalt as the metal catalyst and occurs under rather mild reaction conditions (room temperature). The use of ynamides confers unique reactivity and exclusive regioselectivity.

Synthesis of α-Fluorinated Imides via Direct Fluorohydroxylation of Ynamides.

A practical synthesis of α-fluorinated imides via the catalyst-free fluorohydroxylation of ynamides is developed. The reaction employs commercially available Selectfluor (F-TEDA-BF) and HO as the fluorine and hydroxyl sources, respectively. A broad range of aryl- or alkyl-substituted ynamides were well applicable to the reaction with good functional group tolerance under simple and mild reaction conditions.

Decarboxylative Negishi Coupling of Redox-Active Aliphatic Esters by Cobalt Catalysis.

A cobalt-catalyzed decarboxylative Negishi coupling reaction of redox-active aliphatic esters with organozinc reagents was developed. The method enabled efficient alkyl-aryl, alkyl-alkenyl, and alkyl-alkynyl coupling reactions under mild reaction conditions with no external ligand or additive needed. The success of an in situ activation protocol and the facile synthesis of the drug molecule (±)-preclamol highlight the synthetic potential of this method.

Cp*Co(iii)-Catalyzed oxidative [5+2] annulation: regioselective synthesis of 2-aminobenzoxepines via C-H/O-H functionalization of 2-vinylphenols with ynamides.

A Cp*Co(iii)-catalyzed [5+2] C-H annulation reaction of 2-vinylphenols with ynamides was developed. The reaction led to the efficient synthesis of valuable 2-aminobenzoxepines in high regioselectivity. Mild reaction conditions, good functional group tolerance, and moderate to good yields were observed.

Regioselective Synthesis of 5-Aminooxazoles via Cp*Co(III)-Catalyzed Formal [3 + 2] Cycloaddition of N-(Pivaloyloxy)amides with Ynamides.

A simple and efficient protocol for the regioselective synthesis of 5-aminooxazoles is disclosed. The reaction, catalyzed by a cheap Cp*Co(III) catalyst, starts from easily accessible N-(pivaloyloxy)amides and ynamides. Mild reaction conditions, a broad substrate scope, good functional group tolerance, and good to excellent yields were observed.

Manganese(I)-Catalyzed Regio- and Stereoselective 1,2-Diheteroarylation of Allenes: Combination of C-H Activation and Smiles Rearrangement.

Heteroarenes are important structural motif in functional molecules. A Mn -catalyzed 1,2-diheteroarylation of allenes via a C-H activation/Smiles rearrangement cascade is presented. The reaction occurred under additive-free or even solvent-free conditions, which allowed the creation of two C-C and one C-N bonds in a single operation.

Gold-free ternary III-V antimonide nanowire arrays on silicon: twin-free down to the first bilayer.

With the continued maturation of III-V nanowire research, expectations of material quality should be concomitantly raised. Ideally, III-V nanowires integrated on silicon should be entirely free of extended planar defects such as twins, stacking faults, or polytypism, position-controlled for convenient device processing, and gold-free for compatibility with standard complementary metal-oxide-semiconductor (CMOS) processing tools. Here we demonstrate large area vertical GaAsxSb1-x nanowire arrays grown on silicon (111) by molecular beam epitaxy.

Modelling and engineering of stress based controlled oxidation effects for silicon nanostructure patterning.

Silicon nanostructure patterning with tight geometry control is an important challenge at the bottom level. In that context, stress based controlled oxidation appears to be an efficient tool for precise nanofabrication. Here, we investigate the stress-retarded oxidation phenomenon in various silicon nanostructures (nanobeams, nanorings and nanowires) at both the experimental and the theoretical levels.

Realization of vertical silicon nanowire networks with an ultra high density using a top-down approach.

In this paper, we demonstrate the top-down fabrication of vertical silicon nanowires networks with an ultra high density (4 x 10(10) cm(-2)), a yield of 100%, and a precise control of both diameter and location. Firstly, dense and well-defined networks of nanopillars have been patterned by e-beam lithography using a negative tone e-beam resist Hydrogen SylsesQuioxane (HSQ). A very high contrast has been obtained using a high acceleration voltage (100 kV), very small beam size at a current of 100 pA and a concentrated developer, 25% Tetramethylammonium Hydroxide.