Two-Fold Intramolecular Phosphacyclization: From Fluorescent Diphosphapyrene Salts to Pentavalent Derivatives

Abstract

The synthesis of π-extended pyrene-based luminescent compounds containing two six-membered phosphacycles has been realized through a two-step synthesis. It involves a Cu­(II)-mediated double cyclization of tertiary diphosphane derivatives to afford dicationic molecules with quaternized phosphorus centers. Subsequent transformation of diphosphonium species into the corresponding P-oxide derivatives has been successfully achieved through Pd(0)-assisted cleavage of the P–Ph bonds, which opens a promising way for the functionalization of polyaromatic P-systems.

Bisphosphonium salt catalyzed [3 + 2] annulation of N-tosylimino(iso)quinolinium ylides with aryl olefins under blue LED irradiation

“…25 This intramolecular cyclization of binap with copper(II) under air produced bisphosphonium salt 2a with a yield of only 24% due to the formation of by-products such as phosphine oxide and copper complexes. Based on the literature reports [29][30][31] and our continuing efforts in synthesis of organophosphorus compounds, [32][33][34][35][36][37][38][39] we proposed an oxygen-free procedure to prevent the oxidation of the reactive phosphorus radical cation intermediate by triplet oxygen. 40 The decreased coordination interaction between the phosphorus radical cation and copper cation could improve the reaction efficiency even further.…”