The modular cyanoalkylamination of alkenes using bench-stable
and
easy-to-handle α-imino-oxy acid oxime esters as difunctional
reagents creates new synthetic avenues. A metal-free photosensitization
protocol for the installation of both amino and cyanoalkyl functionalities
onto alkene feedstocks in a single step via two differently reactive
nitrogen-centered radicals was developed via energy-transfer catalysis.
Excellent functional group tolerance and mild reaction conditions
also render this protocol suitable for the cyanoalkylamination of
pharmaceutically relevant molecule-derived alkenes.
A vinyl
radical-mediated 1,5-hydrogen atom transfer strategy for
remote C(sp3)–H imination under visible-light-induced
photochemical metal-free conditions afforded diverse γ-imino
alkenes with excellent stereoselectivity. Oxime ester-based bifunctional
reagents provided not only nucleophilic alkyl radicals for radical
addition reactions with electron-deficient alkynes but also long-lived
steady-state imine radicals for trapping alkyl radicals following
the intramolecular 1,5-hydrogen migration of unstable olefin radicals.
A new class of iminosulfonylation reagents were developed
and extensively
used in the 1,2-iminosulfonylation of various olefins. Olefins containing
bioactive molecules, such as indomethacin, gemfibrozil, clofibrate,
and fenbufen, afforded the desired iminosulfonylation products in
synthetically useful yields. Furthermore, the first remote 1,6-iminosulfonylation
of alkenes was realized by using oxime ester bifunctionalization reagents.
Overall, more than 40 structurally diverse β-imine sulfones
were obtained in moderate to excellent yields.
Functionalized dihydrocoumarins, including 3‐amino‐ and 4‐amino dihydrocoumarins serving as α‐ and β‐amino acid derivatives, have been synthesized using one‐step site‐ and regioselective alkylamination from coumarins. This conversion offers 35 examples in 24% to 81% yields.
A palladium-catalyzed ring-opening [3 + 2]-annulation of spirovinylcyclopropanyl oxindoles with seven-membered cyclic N-sulfonylimines has been developed. A wide range of seven-membered benzosultams featuring both a quaternary center and axially chiral biaryl scaffolds have been afforded in an average yield of 87% with moderate to excellent diastereoselectivities. The enantioenriched benzosultams were also accessed successfully in good yields with excellent atropoenantioselectivities enabled by the Pd 2 (dba) 3 /(S,S,S)-SKP ligand. The practical utility of this protocol was further demonstrated by the gram-scale reaction and diversified synthetic transformations of the desired seven-membered benzosultam.
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