Selective Synthesis of Z-Silyl Enol Ethers via Ni-Catalyzed Remote Functionalization of Ketones.

We report a remote functionalization strategy, which allows the Z-selective synthesis of silyl enol ethers of (hetero)aromatic and aliphatic ketones via Ni-catalyzed chain walking from a distant olefin site. The positional selectivity is controlled by the directionality of the chain walk and is independent of thermodynamic preferences of the resulting silyl enol ether. Our mechanistic data indicate that a Ni(I) dimer is formed under these conditions, which serves as a catalyst resting state and, upon reaction with an alkyl bromide, is converted to [Ni(II)-H] as an active chain-walking/functionalization catalyst, ultimately generating a stabilized η3-bound Ni(II) enolate as the key selectivity-controlling intermediate.

Fine-Grained Visual Recognition in Mobile Augmented Reality for Technical Support.

Augmented Reality is increasingly explored as the new medium for two-way remote collaboration applications to guide the participants more effectively and efficiently via visual instructions. As users strive for more natural interaction and automation in augmented reality applications, new visual recognition techniques are needed to enhance the user experience. Although simple object recognition is often used in augmented reality towards this goal, most collaboration tasks are too complex for such recognition algorithms to suffice. In this paper, we propose a fine-grained visual recognition approach for mobile augmented reality, which leverages RGB video frames and sparse depth feature points identified in real-time, as well as camera pose data to detect various visual states of an object. We demonstrate the value of our approach through a mobile application designed for hardware support, which automatically detects the state of an object to present the right set of information in the right context.

Orthogonal Nanoparticle Catalysis with Organogermanes.

Although nanoparticles are widely used as catalysts, little is known about their potential ability to trigger privileged transformations as compared to homogeneous molecular or bulk heterogeneous catalysts. We herein demonstrate (and rationalize) that nanoparticles display orthogonal reactivity to molecular catalysts in the cross-coupling of aryl halides with aryl germanes. While the aryl germanes are unreactive in Ln Pd0 /Ln PdII catalysis and allow selective functionalization of established coupling partners in their presence, they display superior reactivity under Pd nanoparticle conditions, outcompeting established coupling partners (such as ArBPin and ArBMIDA) and allowing air-tolerant, base-free, and orthogonal access to valuable and challenging biaryl motifs. As opposed to the notoriously unstable polyfluoroaryl- and 2-pyridylboronic acids, the corresponding germanes are highly stable and readily coupled. Our mechanistic and computational studies provide unambiguous support of nanoparticle catalysis and suggest that owing to the electron richness of aryl germanes, they preferentially react by electrophilic aromatic substitution, and in turn are preferentially activated by the more electrophilic nanoparticles.

E-Olefins through intramolecular radical relocation.

Full control over the selectivity of carbon-carbon double-bond migrations would enable access to stereochemically defined olefins that are central to the pharmaceutical, food, fragrance, materials, and petrochemical arenas. The vast majority of double-bond migrations investigated over the past 60 years capitalize on precious-metal hydrides that are frequently associated with reversible equilibria, hydrogen scrambling, incomplete E/Z stereoselection, and/or high cost. Here, we report a fundamentally different, radical-based approach. We showcase a nonprecious, reductant-free, and atom-economical nickel (Ni)(I)-catalyzed intramolecular 1,3-hydrogen atom relocation to yield E-olefins within 3 hours at room temperature. Remote installations of E-olefins over extended distances are also demonstrated.

Chemoselective Pd-Catalyzed C-TeCF3 Coupling of Aryl Iodides.

While the TeCF3 moiety features promising properties and potential in a range of applications, no direct synthetic method exists for its incorporation into aromatic scaffolds. This report features the first direct catalytic method for the formation of C(sp2 )-TeCF3 bonds. The method relies on a Pd/Xantphos catalytic system and allows for the trifluoromethyltellurolation of aryl iodides. Our computational and experimental mechanistic analyses shed light on the privileged activity of Xantphos in this transformation.

Gold-catalyzed oxime-oxime rearrangement.

The gold-catalyzed reaction of pyrrole and indole oximes having a propargyl group attached to the nitrogen atom was studied. The selective 6-endo-dig mode of cyclization was observed for the terminal alkynes giving rise to the formation of pyrazine N-oxides in the presence of a gold catalyst. However, the reaction with substituted alkyne transferred the oxime functionality intramolecularly from one carbon atom to another via the 7-endo-dig cyclization process. This transformation is unprecedented in the literature and is named an oxime-oxime rearrangement.