Synthèse et réactivité de nouveaux a-bromo-g-hydroxybutyrolactames par une MCRs

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A tunable copper-catalyzed multicomponent reaction towards alkaloid-inspired indole/lactam polycycles

International audienceA versatile copper(I)-catalyzed cascade multicomponent reaction strategy between readily available (Z)-3-iodoacrylic acids, terminal alkynes, and primary amines is reported, leading to a great diversity of complex heterocyclic backbones based on biorelevant indole/lactam scaffolds

Forming Weakly Interacting Multilayers of Graphene Using Atomic Force Microscope Tip Scanning and Evidence of Competition between Inner and Outer Raman Scattering Processes Piloted by Structural Defects

We report on an alternative route based on nanomechanical folding induced by an AFM tip to obtain weakly interacting multilayer graphene (wi-MLG) from a chemical vapor deposition (CVD)-grown single-layer graphene (SLG). The tip first cuts and then pushes and folds graphene during zigzag movements. The pushed graphene has been analyzed using various Raman microscopy plots-AD/AG × EL 4 vs ΓG, ω2D vs Γ2D, Γ2D vs ΓG, ω2D+/− vs Γ2D+/−, and A2D−/A2D+ vs A2D/AG. We show that the SLG in-plane properties are maintained under the folding process and that a few tens of graphene layers are stacked, with a limited number of structural defects. A blue shift of about 20 cm−1 of the 2D band is observed. The relative intensity of the 2D− and 2D+ bands have been related to structural defects, giving evidence of their role in the inner and outer processes at play close to the Dirac con

Wrinkling and crumpling in twisted few and multilayer CVD graphene: High density of edge modes influencing Raman spectra

International audienceRichness and complexity of Raman spectra related to graphene materials is established from years to decades, with, among others: the well-known G, D, 2D,... bands plus a plethora of weaker bands related to disorder behavior, doping, stress, crystal orientation or stacking information. Herein, we report on how to detect crumpling effects in Raman spectra, using a large variety of few and multilayer graphene. The main finding is that these crumples enhance the G band intensity like it does with twisted bi layer graphene. We updated the D over G band intensity ratio versus G band width plot, which is generally used to disentangle point and linear defects origin, by reporting surface defects created by crumples. Moreover, we report for the first time on the existence 23 resonant additional bands at 633 nm. We attribute them to edge modes formed by high density of crumples. We use Raman plots (2D bands versus G band positions and widths) to gain qualitative information about the way layers are stacked