Cross-electrophile
coupling reactions of two Csp3–X
bonds remain challenging. Herein we report an intramolecular nickel-catalyzed
cross-electrophile coupling reaction of 1,3-diol derivatives. Notably,
this transformation is utilized to synthesize a range of mono- and
1,2-disubstituted alkylcyclopropanes, including those derived from
terpenes, steroids, and aldol products. Additionally, enantioenriched
cyclopropanes are synthesized from the products of proline-catalyzed
and Evans aldol reactions. A procedure for direct transformation of
1,3-diols to cyclopropanes is also described. Calculations and experimental
data are consistent with a nickel-catalyzed mechanism that begins
with stereoablative oxidative addition at the secondary center.
The instruction of high enrollment general and organic chemistry laboratories at a large public 10 university always have curricular, administrative, and logistical challenges. Herein, we describe how we met these challenges in the transition to remote teaching during the COVID-19 pandemic. We discuss the reasoning behind our approach, the utilization of our existing web-based course content, the additions and alterations to our curriculum, replacement of experimental work with videos, the results of both student and TA surveys, and lessons learned for iterations of these courses in the near 15 future. File list (3) download file view on ChemRxiv CHEMRXIV_REVISED-Online in No Time.pdf (1.34 MiB) download file view on ChemRxiv Online in No Time Supporting Information.pdf (181.10 KiB) download file view on ChemRxiv bigbrother_python_code.py (3.15 KiB)
The instruction of high enrollment general and organic chemistry laboratories at a large public
10 university always have curricular, administrative, and logistical challenges. Herein, we describe how
we met these challenges in the transition to remote teaching during the COVID-19 pandemic. We
discuss the reasoning behind our approach, the utilization of our existing web-based course content,
the additions and alterations to our curriculum, replacement of experimental work with videos, the
results of both student and TA surveys, and lessons learned for iterations of these courses in the near
15 future.
Development of nickel-catalyzed transformations would be facilitated by an improved ability to predict which ligands promote and suppress competing mechanisms. We evaluate ligand-based modulation of catalyst preference for one-or two-electron pathways employing 4halotetrahydropyrans as model substrates that can undergo divergent reaction pathways. Chemoselectivity for one-or two-electron oxidative addition is predicted by ligand class. Phosphine-ligated nickel catalysts favor closed-shell oxidative addition. In contrast, nitrogen-ligated nickel catalysts prefer the one-electron pathway, initiating with halogen atom transfer.
We
have established a nickel-catalyzed domino reaction that harnesses
sulfonamide, alkyl chloride, and alkyne functionalities in a multistep
sequence to afford vinylcyclopropanes bearing tetrasubstituted olefins.
The starting materials are prepared by iron-promoted aza-Prins reactions
of ynals. This method provides rapid synthetic access to valuable
building blocks with applications in medicinal chemistry. Experimental
and computational results support the initiation of the catalytic
cycle by oxidative addition of the propargylic sulfonamide, and a
key ambiphilic allenylnickel intermediate leads to a bifurcated reaction
pathway that generates olefin isomers.
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