Biographical radiation-induced defect formation as a method for the activation of red phosphorus in reactions with arylalkenes

Abstract

In recent years, it has been reported that the modifica tion of the chemical properties of red phosphorus (both in inorganic1—2 and organic3—6 processes) can be regulated by controlled defect formation in its structure. New data on the effect of biographical defects on the reactivity of elementary phosphorus were obtained in di rect phosphorylation of arylalkenes in a KOH—DMSO system. Red phosphorus *Pn synthesized by radiation induced polymerization of white phosphorus in benzene (with 60Co as the radiation source) and containing P— P—R type defects (R is a benzene fragment)5 reacts with styrene at room temperature to give diphenethylphosphine oxide (1) and phenethylphosphinic acid (2) in a total yield of 15%. With commercial red phosphorus Pn pro duced by thermal polymerization of white phosphorus, the total yield of organophosphorus compounds 1 and 2 did not exceed 2%. Under similar conditions, white phos phorus P4 is more reactive: the total yield of compounds 1 and 2 is 30%. In phosphorylation of 2 vinylnaphthalene (90—96 °C), defective *Pn is superior to both Pn and P4 to give tris[2 (2 naphthyl)ethyl]phosphine oxide (3), 2 (2 naph thyl)ethylphosphinic acid (4), and bis[2 (2 naph thyl)ethyl]phosphine oxide (5) as the major reaction prod ucts in a total yield of 73% (product ratio 1.6 : 1.2 : 1). Under comparable conditions, phosphorylation of 2 vinylnaphthalene with P4 or Pn is less efficient but more selective (phosphine oxide 3 is formed in 58 and 44% yield, respectively). In addition, the above reaction with Pn affords acid 4 in 11% yield. The formation of oxygen containing compounds 1—5 seems to be in accord with the proposed mechanism.7 Compounds 1—5 were isolated and identified by com paring their 1H and 31P NMR spectra (Bruker DPX 400; 400 and 161.98 MHz, respectively; CDCl3) with spectro scopic data for authentic samples.8,9