Ruthenium-catalyzed reduction of N-alkoxy- and N-hydroxyamides

Photocatalytic Generation of a Ground-State Electron Donor Through Water Activation

Electron donors that can be excited to higher energy states through light absorption can achieve oxidation potentials as low as -3.0 V (vs. SCE). However, ground-state organic electron transfer reagents operating at such potentials remain underdeveloped, often necessitating multi-step syntheses and elevated reaction temperatures for activation. The longer lifetime of ground-state reagents is an advantage compared to most photoexcited single-electron reductants, which typically have relatively short lifetimes. In this study, catalytically generated phosphine oxide radical anions derived from phosphines and water applying redox catalysis are introduced as highly efficient single-electron reductants. The in situ generated radical anions are capable of reducing electron-rich aryl chlorides at potentials as low as -3.3 V (vs. SCE). Cyclic voltammetry studies and DFT calculations provide valuable insights into the behavior of these phosphorus-based ground-state electron donors. These findings do not only expand the chemistry of phosphoranyl radicals but also unlock the potential of in situ generated organic ground state electron donors that reach potentials comparable to elemental potassium.

Ruthenium(ii)-catalyzed reductive N–O bond cleavage of N-OR (R = H, alkyl, or acyl) substituted amides and sulfonamides

A convenient method for the reductive cleavage of the N–O bonds of amide derivatives was developed using ruthenium(ii)-catalyzed transfer hydrogenation reaction.

Dealkoxylation of N-alkoxyamides without an external reductant driven by Pd/Al cooperative catalysis

Lewis acid-assisted palladium-catalysed dealkoxylation of N-alkoxyamides has been realised in the absence of an external reductant.

Reductive cleavage of the N–O bond: elemental sulfur-mediated conversion of N-alkoxyamides to amides

By treating with elemental sulfur in the presence of DABCO in DMSO, a variety of N-alkoxyamides were readily converted to amides in satisfactory to excellent yields via a metal-free reductive cleavage of the N–O bond.

Transition-Metal-Free Synthesis of N-Hydroxy Oxindoles by an Aza-Nazarov-Type Reaction Involving Azaoxyallyl Cations

A novel transition-metal-free method to construct N-hydroxy oxindoles by an aza-Nazarov-type reaction involving azaoxyallyl cation intermediates is described. A variety of functional groups were tolerated under the weak basic reaction conditions and at room temperature. A one-pot process was also developed to make the reaction even more practical. This method provides alternative access to oxindoles and their biologically active derivatives.

Total Synthesis of (±)-Minfiensine via a Formal [3+2] Cycloaddition

(±)-Minfiensine (1) was synthesized in 10 steps in 26% overall yield with the 1,2,3,4-tetrahydro-9a,4a-iminoethanocarbazole core constructed through a [3+2] cycloaddition reaction between indole and an azaoxyallylic cation.

Enantioselective Rh-Catalyzed Carboacylation of C═N Bonds via C-C Activation of Benzocyclobutenones

Herein we describe the first enantioselective Rh-catalyzed carboacylation of oximes (imines) via C-C activation. In this transformation, the benzocyclobutenone C1-C2 bond is selectively activated by a low valent rhodium catalyst and subsequently the resulting two Rh-C bonds add across a C═N bond, which provides a unique approach to access chiral lactams. A range of polycyclic nitrogen-containing scaffolds were obtained in good yields with excellent enantioselectivity. Further derivatization of the lactam products led to a rapid entry to various novel fused heterocycles.

Direct reductive coupling of indoles to nitrostyrenes en route to (indol-3-yl)acetamides

A highly efficient one-pot method for the reductive coupling of indoles to nitrostyrenes in PPA doped with PCl₃ was developed. This method allows direct access to primary (indol-3-yl)acetamides, interesting as anti-cancer drug candidates.