Electrochemical Synthesis of O‐Phthalimide Oximes from α‐Azido Styrenes via Radical Sequence: Generation, Addition and Recombination of Imide‐N‐Oxyl and Iminyl Radicals with C−O/N−O Bonds Formation

Abstract

Electrochemically induced radical‐initiated reaction of vinyl azides with N‐hydroxyphthalimide resulting O‐phthalimide oximes with challenging for organic chemistry N−O‐N fragment has been discovered. The developed approach introduces in synthesis electrochemically generated O‐centered imide‐N‐oxyl radicals as the coupling components. Sequential formation of C−O and N−O bonds was achieved via generation and selective addition of imide‐N‐oxyl radicals, followed by recombination with iminyl radicals. A wide range of O‐phthalimide oximes was obtained with the yields up to 84%.

Oxime‐Derived Iminyl Radicals in Selective Processes of Hydrogen Atom Transfer and Addition to Carbon‐Carbon π‐Bonds

“…Future development areas of the oxime‐derived iminyl radicals chemistry include: (1) the development of mild conditions for the use of easily accessible oxime derivatives as iminyl radicals precursors, (2) further mechanistic studies of complicated radical reactions of oximes involving N−O bond cleavage (some representative examples of such processes are discussed in “Other reactions of oxime‐derived iminyl radicals” section), (3) the development of new photocatalytic systems, especially those based on non‐precious metals, metal‐free systems, or recyclable heterogenous photocatalysts (4) the development of electrochemical approaches to the generation of iminyl radicals. In addition, synthetic potential of some types of iminyl radicals reactivity, such as intermolecular N−O and N−N coupling is still to be realized for oxime‐derived iminyl radicals [55,56,161–164] …”

“…In recent years, oxime derivatives have found broad applications as precursors of iminyl radicals generated by N−O bond cleavage. Other approaches to iminyl radicals, such as radical addition to isonitriles [48–50] or vinyl azides, [51–58] are useful for specific radical structure types. The oxime‐based strategy allows for generation of diverse iminyl radicals from widely available carbonyl compounds that can be easily transformed into oximes.…”

Electrochemical Generation and Use in Organic Synthesis of C‐, O‐, and N‐Centered Radicals

“…O ‐phthalimide oximes ( 289 ) were electrochemically prepared using the mediator system NHPI/PINO, from α‐azido styrenes ( 287 ) (Scheme 32) [179] . The reaction involves the electrochemical generation of a phthalimide‐ N ‐oxyl (PINO) radical ( 291 ) and its subsequent addition to the olefin moiety.…”

Recent Advances in Paired Electrosynthesis

“…Electroorganic reactions are based either on single electron transfer at the electrode surface to give radical intermediates (followed by homogeneous reaction steps in solution) or on heterogeneous multi‐electron transfer on catalytic electrode surfaces, where interactions with the substrate material provide conditions for multi‐step reaction pathways. Radical intermediates generated homogeneously in single electron transfer processes can lead to interesting reaction products [21] . Mediated electrosyntheses, for example based on halogen reaction intermediates, [22] allows highly reactive (and potentially dangerous) species to be generated in situ and in low concentration.…”