The copper-catalyzed carbomagnesiation reaction of cyclopropenyl esters 1 leads to various substituted cyclopropanes species 3 in good yields with very high diastereoselectivities. The reaction proceeds through a syn-chelated carbomagnesiation reaction and could be extended to various cyclopropenylmethyl ester derivatives 5. The potential of this approach was illustrated by the preparation of two consecutive all-carbon quaternary stereocenters. However, the carbometalation reaction needs to be performed at temperature ranging from -35 to -20 °C to avoid subsequent fragmentation reaction into stereodefined β,γ-nonconjugated unsaturated esters 4. Alternatively, the carbocupration reaction with organocopper species could also be performed to leads to configurationally stable cyclopropyl copper species 2[Cu]. Additionally, when the Lewis acid character of the copper center is decreased (i.e., RCuCNLi), the reaction proceed with an anti-selectivity. The diastereodivergent behavior of these organometallic species is of synthetic interest, since both diastereomers syn-3 and anti-3 can be obtained, at will, from the same precursor cyclopropenyl esters 1.

A new strategy has been developed to construct enantiomerically enriched allylic quaternary carbon stereocenters in a single-pot operation through a combined carbometalation/zinc homologation/fragmentation sequence.

Associating atomic vacancies to excited-state transport phenomena in two-dimensional semiconductors demands a detailed understanding of the exciton transitions involved. We study the effect of such defects on the electronic and optical properties of WS 2 −graphene and MoS 2 −graphene van der Waals heterobilayers, employing many-body perturbation theory. We find that chalcogen defects and the graphene interface radically alter the optical properties of the transition-metal dichalcogenide in the heterobilayer, due to a combination of dielectric screening and the manybody nature of defect-induced intralayer and interlayer optical transitions. By analyzing the intrinsic radiative rates of the subgap excitonic features, we show that while defects introduce low-lying optical transitions, resulting in excitons with non-negligible oscillator strength, they decrease the optical response of the pristine-like transition-metal dichalcogenide intralayer excitons. Our findings relate excitonic features with interface design for defect engineering in photovoltaic and transport applications.

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For each goal, a metal!  A simple set of carbometalation‐based sequences transform readily available cyclopropene esters into a diverse variety of chiral building blocks, including quaternary stereocenters or stereodefined double bonds. Yields are high and the excellent diastereoselectivity is metal‐additive controlled. For more details see the Full Paper by I. Marek et al. on