Phosphines reactions with arynes

Reactions of phosphines and phosphites have received some attention but their preparative value is limited. The zwitterion formed from diphenylmethylphosphine and benzyne rearranges to ylide (124) which can be captured by Wittig alkenation, with cyclohexanone, in about 20% yield.159 Some synthetically useful reactions of tellurium and selenium compounds with arynes have been reported. For example, heating diphenyl iodonium carboxylate and bis(p-ethoxyphenyl) ditelluride in dichlorobenzene affords the compound (125).160 The corresponding reactions with diphenyl selenide and diphenyl sulfide... 

The tantalum-benzyne complex (130) is much less reactive than other early transition-metal aryne complexes. It shows no reaction with acetone, benzophenone, benzaldehyde, acetonitrile, 3-hexyne, or methanol. The lack of reactivity of 130 was attributed to nonlability of the PMe3 ligand. Indeed, no phosphine exchange was observed when 130 was mixed with an excess of PMe3-d9. Refluxing 129 in a mixture of methanol and toluene (3 10 v/v) leads to clean formation of 131. This presumably results from reaction of a 16-electron benzyne complex with the alcohol. 

A final example of aryne formation involves the reaction of o-phenylene carbonate (90) with phosphines. An analogous reaction with thiocarbonates (91) fails as does generation of the anion of 2-phenyl-1,3-benzodioxole (92), which had been expected to lose benzoate ion to give benzyne. ... 

Arynes combine with all kinds of polar compounds such as lithium halide, alcohols, primary, secondary or tertiary amines, phosphines, and boranes. Of practical, even technical, importance are their reactions with metal hydroxides and alkoxides. The conversion of chlorobenzene by sodium hydroxide at 350 °C into sodium phenolate, an industrial process, obeys the elimination/addition mechanism. Again arynes can be postulated as plausible intermediates. Regardless of which isomer of bromophenol or of bromophenyl benzenesulfonate is heated with sodium hydroxide, resorcinol is always isolated as the main or sole product after neutralization. 

The addition of secondary phosphites to arynes is an attractive procedure for the formation of arylphosphonates (Schemes 4.211 and 4.212) [332]. The resulting arylphosphonates were formed in moderate to excellent yields, and a range of substrates were compatible with the reaction chemistry with the provision that they possessed a TMS group adjacent to a triflate. In addition to the tertiary phosphites, diethyl phenylphosphonite was successfully added to the arynes to generate arylphosphinates. This approach is a potentially valuable way to generate arylphosphonates or phosphinates under mild conditions without the addition of transition metals. 

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