Transition metal-promoted reactions of diarylphosphine oxides as a synthetic method for organophosphorus heterocyclic compounds

Evaluation of Transition Metal Catalysts in Electrochemically Induced Aromatic Phosphonation

Voltammetry provides important information on the redox properties of catalysts (transition metal complexes of Ni, Co, Mn, etc.) and their activity in electrocatalytic reactions of aromatic C–H phosphonation in the presence of a phosphorus precursor, for example, dialkyl-H-phosphonate. Based on catalytic current growth of oxidation or reduction of the metal catalysts (Co^II, Mn^II, Ni^II, Mn^II/Ni^II, Mn^II/Co^II, and Co^II/Ni^II), quantitative characteristics of the regeneration of catalysts were determined, for example, for Mn^II, Ni^II and Mn^II/Ni^II, Co^II/Ni^II pairs. Calculations confirmed the previously made synthetic observations on the synergistic effect of certain metal ions in binary catalytic systems (Mn^IIbpy/Ni^IIbpy and Ni^IIbpy/Co^IIbpy); for mixtures, the observed rate constants, or TOF, were 690 s⁻¹ and 721 s⁻¹, respectively, and product yields were higher for monometallic catalytic systems (up to 71% for bimetallic catalytic systems and ~30% for monometallic catalytic systems). In some cases, the appearance of pre-waves after adding H-phosphonates confirmed the preceding chemical reaction. It also confirmed the formation of metal phosphonates in the time scale of voltammetry, oxidizing or reducing at lower potentials than the original (RO)₂P(O)H and metal complex, which could be used for fast diagnostics of metal ion and dialkyl-H-phosphonate interactions. Electrochemical transfer of an electron to (from) metal phosphonate generates a phosphonyl radical, which can then react with different arenes to give the products of aromatic C–H phosphonation.

Regioselective radical arylation: silver-mediated synthesis of 3-phosphorylated coumarins, quinolin-2(1H)-one and benzophosphole oxides

A silver-mediated domino radical addition/cyclization reaction of diaryl- or dialkyl-phosphine oxides with propynoic acid derivatives delivering 3-phosphorylated coumarins, quinolin-2(1H)-one and benzophosphole oxides is presented.

Manganese(iii)-mediated selective phosphorylation of enamides: direct synthesis of β-phosphoryl enamides

Mn(iii)-Mediated radical oxidative selective phosphorylation ofN-styrylamides to afford β-phosphoryl enamides, which could be easily transformed to β-amino phosphonic acids, is described.

Opportunities and challenges for combining electro- and organometallic catalysis in C(sp2)-H phosphonation

The chemistry of organoelemental compounds including carbon-phosphorus derivatives is now one of the most rapidly developing fields of research, regarding both fundamental science and solution of applied problems. Extensive opportunities for the synthesis of organophosphorus compounds are opened up by the use of unconventional methods, first of all, electrochemical ones, which combine the benefits of usual homogeneous chemistry in solution and electrochemistry, where reactants are generated at the electrodes directly in the reaction system. The interest in the organic electrosynthesis is caused by several factors, including mild conditions (room temperature, atmospheric pressure), the possibility of conducting reactions in a closed system with a low concentration of the catalyst, which is readily regenerated. This mini-review generalizes the achievements in the field of development of new electrochemical, efficient and atom-economical, catalytic methods for the formation of aromatic carbon – phosphorus bonds and some historical background of these approaches.