Manganese-Catalyzed and Mediated Synthesis of Arylphosphinates and Related Compounds

Abstract

The free-radical arylation of H-phosphinates and related compounds was examined. A practical catalytic process with the air as the oxidant could not be found. However, an inexpensive and robust methodology was developed, using catalytic Mn(II) as the radical initiator and excess Mn(IV) as the stoichiometric oxidant. Using these conditions, the inter-and intramolecular arylation of phosphinylidene compounds has a broad scope, including application to the synthesis of P-heterocycles. A full account of this methodology is presented including a discussion of its limitations.

Disulfide Promoted C−P Bond Cleavage of Phosphoramide: “P” Surrogates to Synthesize Phosphonates and Phosphinates

“…Since we estimated the molecular weight of the intermediates S3 and S4 in HRMS, we speculate that the reaction is more likely to proceed through path a . Furthermore, since P(III)−H was extremely sensitive to air and was easily oxidized, in the absence of a disulfide, substrate 1B can be directly oxidized to phosphoric acid 7 [28c,f] …”

Electrochemical C–H phosphorylation of arenes in continuous flow suitable for late-stage functionalization

“…1b). In these reactions, either the arene or the phosphorus coupling partner is oxidized under photochemical 14,15 or transition-metal catalyzed 16,17 conditions to a radical intermediate, which then reacts with the other coupling partner to achieve C-P bond formation. These radical-based reactions are generally limited to electron-rich arenes or azoles [18][19][20][21] due to the need to oxidize the arene to a radical cation and the moderate reactivity of the neutral P-radicals.…”

Microwave-assisted synthesis of benzo[b]phosphole oxide derivatives by oxidative addition of acetylenes and secondary phosphine oxides or alkyl phenyl-H-phosphinates

“…In contrast to previous reports published in this topic [4,6,[12][13][14][15][16][17][18], our method developed is the first MW-assisted approach for the synthesis of benzo[b]phosphole oxides, which allows the reactions to take place faster (2-3 h instead of 8-24 h) and applies a modestly toxic solvent (MeCN). Altogether 16 derivatives were prepared in good to high yields, among them 12 are new, which were characterized by 31 P, 1 H, and 13 C NMR spectroscopy, as well as by HRMS.…”

“…Although the oxidative addition means a huge improvement as compared to the early syntheses, the development of this reaction type is quite requiring, especially regarding the reaction time. The literature survey revealed that several oxidizing agents were tried out, however, usually a long time is needed for a complete reaction: Ag2O − 8-10 h [6,12], AgOAc − 4-18 h [13][14][15], Mn(OAc)2/MnO2 − 4 h [16], K2S2O8 − 24 h [4] and N-etoxy-2methylpyridinium tetrafluoroborate − 48 h [17]. In one example, the oxidative addition could be accomplished under 30 min, however, a catalyst (CuSO4) and a base (NH3) had to be applied beside the t-butyl hydroperoxide oxidant [18].…”