Compounds Containing a Spiro Phosphorus Atom

A quest for stable phosphonyl radicals: limitations and possibilities of carbocyclic backbones and bulky substituents

“…Another reason for selecting these three radicals is that well-established, straightforward synthetic methodologies are available to obtain possible precursors (phosphine oxides) to them, even with fused rings. 52…”

“…Dalton Transactions synthetic methodologies are available to obtain possible precursors ( phosphine oxides) to them, even with fused rings. 52 To evaluate the possible stabilisation effect of ring fusion, radicals 8, 12, and 22 were placed as central cores into annulations with cyclopentadiene and benzene (Fig. 5), and the corresponding RSE values were obtained at two different levels of theory (Table 2).…”

“…As the appealing characteristics of the P–C covalent bond ( e.g. , substantial bond strength, typical insensitivity toward hydrolysis) paved the way for a plethora of carbocyclic phosphine oxides, 52 we hypothesise that such heterocycles could be feasible and easily accessible precursors to stable phosphonyl radicals. In addition, due to the moderate electronegativity of carbon, we envision that the P-centres would not be strongly influenced by σ-withdrawal, which usually destabilises the phosphonyl radicals (see above).…”