P-ligand-free, microwave-assisted variation of the Hirao reaction under solvent-free conditions; the P–C coupling reaction of >P(O)H species and bromoarenes

Environmentally Friendly Chemistry with Organophosphorus Syntheses in Focus

“…Many variations were elaborated in the last two decades [35,36]. It is noteworthy that the Pd-catalyzed reaction took place efficiently in the presence of Pd(OAc) 2 without any ligand on MW irradiation (Scheme 4) [37]. The corresponding products (5) were formed in high yields (73-95%).…”

Microwave-Assisted Syntheses in Organic Chemistry

“…Many publications highlight the beneficial effect of MW irradiation in the Hirao reaction [20][21][22][23]. Keglevich and Jablonkai developed the first P-ligand-and solvent-free Pd-calayzed coupling of different >P(O)H species with aryl-bromides in the presence of Pd(OAc) 2 under MW conditions (Scheme 2.10) [24]. This accomplishment is the first example for P-ligand-free Hirao reactions.…”

The Use of MW in Organophosphorus Chemistry

“…It was interesting to find that there is no need to use the expensive Pd(Ph 3 P) 4 catalyst in the coupling reaction of dialkyl phosphites with bromobenzene, as Pd(OAc) 2 also catalyses the Hirao reaction in the absence of any added P-ligand. A MW-assisted solvent-free accomplishment was the best choice [42,43]. The arylphosphonates (30) were obtained in 69-93 % yields (Scheme 3.17).…”

“…Products 39 and 40 were obtained, with one exception, in good yields. Depending on the molar ratio of the reactants and the conditions (temperature and reaction time), the addition of dialkyl phosphites or diphenylphosphine oxide to the triple bond of dimethyl acetylenedicarboxylate resulted in the formation of a comparable mixture of the corresponding monoadduct (41) and bisadduct (42), or the bisadduct (42) as the predominating or exclusive product (Scheme 3.29, Table 3.7) [61].…”