Radical Addition Reactions of Phosphorus Hydrides: Tuning the Reactivity of Phosphorus Hydrides, the Use of Microwaves and Horner–Wadsworth–Emmons‐Type Reactions

Abstract

The reactivity of phosphorus hydrides in radical addition reactions are compared, and the substituents on phosphorus are shown to affect the efficiency of the reactions. The change in reactivity is attributed to the different bond dissociation energies of the P–H bonds, which have been calculated. Phosphorus hydrides with particularly weak P–H bonds are shown to undergo radical additions by microwave irradiation, in the absence of conventional initiators. These radical addition reactions produce phosphonothioates, phosphinothioates and phosphane sulfides, which react in HWE‐type reactions, to afford substituted alkenes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Crystal Structure of Bis(2,4,6-trimethylphenyl)-phosphine Oxide

“…The 31 P{ 1 H} NMR spectrum contained one resonance at 10.1 ppm. All resonances in the 13 The NMR spectroscopic data in CDCl 3 for the title compound were consistent with previous reports [16]. The 1 H NMR spectrum contained resonances at 6.86 (d, 4 J HP = 3.7 Hz), 2.39, and 2.28 ppm for the meta-aromatic, ortho-methyl, and para-methyl positions of the mesityl groups, respectively.…”

“…These compounds are precursors to phosphinoyl radicals; they are effective reagents in phosphorylation reactions [10][11][12] due to the accessible P-H bond dissociation energies (ca. 80 kcal mol −1 ) [13], and also participate in olefin addition reactions [14,15]. Given the utility of these compounds, it seemed pertinent to report the single crystal structure of the title compound bis(2,4,6-trimethylphenyl)phosphine oxide, 1.…”

Phosphorus‐Bearing Lithium Compounds in Modern Synthesis

“…Phosphinothioates and phosphane sulfides are the most recent members incorporated into this family of olefination reagents [12]. An attractive application of these anions is the one-pot synthesis of the racemic form of the natural product (±)-2-cyclohexyleicosane 26, isolated from the plant Aeonium lindleyi [13].…”

Radicals in organic synthesis. Part 1

“…The reactivity of these reagents mirrored the theoretical bond dissociation energies of the P-H bond calculated by density functional theory (DFT); those compounds with the weakest P-H bond react faster with alkenes. 314 Diphenylphosphine sulfide adds to a variety of mono-and di-substituted alkenes as well as permitting addition to electron-deficient alkenes, a process that is normally quite challenging to electrophilic P-centred radicals. 315 The electrophilic nature of P-centred radicals has facilitated the development of methodology for the synthesis of phosphonylated cyclic ethers, compounds that show a remarkable similarity to a range of biologically important b-alkoxy phosphonates.…”

“…Alternatively, microwave heating results in a more rapid reaction (93% of 502 after 1 h). 314 Amongst the many advantages that radicals display, compared to ionic systems, is their impunity to water. The main stumbling point to exploiting this is the limited solubility of most organic compounds in water.…”