Microwave-assisted Hirao reaction: recent developments

Abstract

Organic molecules containing phosphorus, now, constitute a major branch of chemistry, and offer fascinating possibilities for their structural, synthetic, and mechanistic study as well as promising biological activities. Organophosphorus compounds find numerous potential applications in the areas of industrial, agricultural, and medicinal chemistry. Aryl-and vinyl-phosphonates are an important class of organophosphorus compounds with potential biological relevance. The Hirao reaction offers a way to access these compounds through phosphorus-carbon (P-C) cross-coupling of aryl and vinyl halides with O,O-dialkyl phosphites, and this reaction has attained a commendable development in many ways in regard to the diversity in the substrates, [P(O)H species, catalysts, and reaction conditions. The present article deals with such developments that occurred under the influence of microwave irradiation.

Syntheses and Reactions of Pyrroline, Piperidine Nitroxide Phosphonates

“…To obtain the five-membered vinylphosphonate, we attempted heating of compound 15 [40] with diethylphosphite in the presence of a catalytic amount of NiCl 2 [41], but no conversion was observed. Our efforts to construct a P-C bond with diethylphospite via the Pd-catalyzed Hirao reaction with the conventional or microwave-assisted method [42] also failed. As a result, we finally decided to lithiate [43] the O-methyl derivative 16, as achieved via Fenton reaction in a dimethylsulfoxide/H 2 O 2 /Fe 2+ system [44], followed by treatment with 1.0 eq.…”

Highly efficient and well-defined phosphinous acid-ligated Pd(ii) precatalysts for Hirao cross-coupling reaction

“…16 Green approaches for making C SP 2-P(vO) bonds are important in synthetic chemistry: for instance, the use of microwave-assisted methodology in the hope of shortening the reaction time. 13,[17][18][19][20][21][22] With the aid of microwave apparatus, Keglevich et al reported catalyst-free, 23 ligand-free 24 and ligand-free/ solvent-free 25,26 conditions for coupling C SP 2-P(vO) bonds. In addition to a recently developed photocatalyst-free (transitionmetal-free) method for making valuable organophosphorus compounds, 27 importantly, Montchamp et al demonstrated that the C SP 2-P(vO) coupling of 2-chloropyrazine was successfully catalysed by 1 mol% of an in situ Pd(OAc) 2 /dppf catalytic system.…”