An Azophosphine Synthetic Equivalent of Mesitylphosphaazide and Its 1,3-Dipolar Cycloaddition Reactions

Dibenzo-7-phosphanorbornadiene-substituted diazene MesN(2)PA (1, where Mes = mesityl, A = anthracene, or C14H10), a synthetic equivalent of mesitylphosphaazide (MesN(2)P) and anthracene, was synthesized by treatment of [Ph(3)BPA][Na(OEt2)(2)] with [MesN(2)]OTf (OTf = CF3SO3-) in thawing tetrahydrofuran (14% isolated yield). Treatment of 1 with unsaturated molecules cyclooctyne, [Na(dioxane)(2.5)][OCP] (phosphaethynolate), and Ad-C P (Ad = adamantyl) results in the corresponding [3 + 2] phosphaazide-(phospha)alkyne cycloadducts, with concomitant loss of anthracene in 65%, 49%, and 38% isolated yield, respectively. Structural data for the phosphaethynolate cycloadduct ([3][Na(12-crown-4)(2)]) were obtained in a single-crystal X-ray diffraction study. A diazatriphosphole was generated by combining 1 with P(2)A(2), a thermally activated anthracenebased molecular precursor to diphosphorus (P-2). Thermolysis (33-65 degrees C) of 1 in benzene-d6 leads to anthracene extrusion. This process has a unimolecular kinetic profile and proceeds with activation parameters of Delta H-double dagger = 21.6 +/- 0.3 kcal/mol and Delta S-double dagger = -4.9 +/- 0.8 cal/(mol K).

Automated summary

A novel diazene compound was synthesized in this study, which underwent a series of reactions to form corresponding cycloadducts. Structural data of the cycloadducts were obtained, and the thermolysis process of this compound along with its kinetic parameters were investigated.