Acyl-Directed ortho-Borylation of Anilines and C7 Borylation of Indoles using just BBr3.

Indoles are privileged heterocycles found in many biologically active pharmaceuticals and natural products. However, the selective functionalization of the benzenoid moiety in indoles in preference to the more reactive pyrrolic unit is a significant challenge. Herein we report that N-acyl directing groups enable the C7-selective C-H borylation of indoles using just BBr3 . This transformation shows some functional-group tolerance and notably proceeds with C6 substituted indoles. The directing group can be readily removed in situ and the products isolated as the pinacol boronate esters. Acyl-directed electrophilic borylation can be extended to carbazoles and anilines with excellent ortho selectivity. 4-amino-indoles are amenable to this process, with acyl group installation and directed electrophilic C-H borylation enabling selective formation of C5-BPin-indoles.

Selective Boryl-Anion Migration in a Vinyl sp2 -sp3 Diborane Induced by Soft Borane Lewis Acids.

An intramolecular 1,2-boryl-anion migration from boron to carbon has been achieved by selective activation of the π system in [(vinyl)B2 Pin2 )]- using "soft" BR3 electrophiles (BR3 =BPh3 or 9-aryl-BBN). The soft character is key to ensure 1,2-migration proceeds instead of oxygen coordination/B-O activation. The BR3 -induced 1,2-boryl-anion migration represents a triple borylation of a vinyl Grignard reagent using only B2 Pin2 and BR3 and forms differentially protected 1,1,2-triborylated alkanes. Notably, by increasing the steric bulk at the ß position of the vinyl Grignard reagent used to activate B2 Pin2 , 1,2-boryl-anion migration can be suppressed in favor of intermolecular {BPin}- transfer to BPh3 , thus enabling simple access to unsymmetrical sp2 -sp3 diboranes.

A Zinc Catalyzed C(sp3 )-C(sp2 ) Suzuki-Miyaura Cross-Coupling Reaction Mediated by Aryl-Zincates.

The Suzuki-Miyaura (SM) reaction is one of the most important methods for C-C bond formation in chemical synthesis. In this communication, we show for the first time that the low toxicity, inexpensive element zinc is able to catalyze SM reactions. The cross-coupling of benzyl bromides with aryl borates is catalyzed by ZnBr2 , in a process that is free from added ligand, and is compatible with a range of functionalized benzyl bromides and arylboronic acid pinacol esters. Initial mechanistic investigations indicate that the selective in situ formation of triaryl zincates is crucial to promote selective cross-coupling reactivity, which is facilitated by employing an arylborate of optimal nucleophilicity.

Fabrication of crystals from single metal atoms.

Metal nanocrystals offer new concepts for the design of nanodevices with a range of potential applications. Currently the formation of metal nanocrystals cannot be controlled at the level of individual atoms. Here we describe a new general method for the fabrication of multi-heteroatom-doped graphitic matrices decorated with very small, ångström-sized, three-dimensional (3D)-metal crystals of defined size. We irradiate boron-rich precious-metal-encapsulated self-spreading polymer micelles with electrons and produce, in real time, a doped graphitic support on which individual osmium atoms hop and migrate to form 3D-nanocrystals, as small as 15 Å in diameter, within 1 h. Crystal growth can be observed, quantified and controlled in real time. We also synthesize the first examples of mixed ruthenium-osmium 3D-nanocrystals. This technology not only allows the production of ångström-sized homo- and hetero-crystals, but also provides new experimental insight into the dynamics of nanocrystals and pathways for their assembly from single atoms.