Thionation of the 2‐λ⁵‐Phosphaquinolin‐2‐one Scaffold with Lawesson's Reagent

Abstract

Lawesson's reagent is one of the most common thionating reagents that has found use for several decades on a variety of carbonyl systems. Herein, we report the transformation of the 2‐λ5‐phosphaquinolin‐2‐one structure to its respective 2‐λ5‐phosphaquinolin‐2‐thione derivative. Solution‐state characterization of both P−OPh and P−Ph thio analogues, as well as solid‐state structures for the latter system, are reported.

Azaphosphinines and their derivatives

“…In 2020, our lab outlined a protocol for the thionation of the benzo[ e ]-fused systems using Lawesson's reagent (Scheme 43). 84 The reaction was conducted on both P -phenoxy 100 and P -phenyl 105 . Comparison of the photophysical properties of the thionated heterocycles 109 to the previously synthesized oxo-analogues (Table 10) showed that there was no apparent change to the absorption profiles upon thionation; however, it was noted that there was a substantial reduction in brightness values and a consistent ∼20 nm redshift of emission, which was attributed to a lower S 1 excited state level resulting from the weaker P–S bond.…”

2-λ5-Phosphaquinolin-2-ones as Non-cytotoxic, Targetable, and pH-Stable Fluorophores

“…Recently, we reported that the phosphorus- and nitrogen-containing (PN) scaffold built from a 2-λ 5 -phosphaquinolin-2-one framework (Figure ) possesses interesting photophysical properties, which include coumarin-like fluorescence emission of 450–650 nm, quantum yields up to 93%, structural modularity, and Stokes shifts ranging from 3800–10 000 cm –1 . , In addition to a variety of studies examining the effects of arene core modification and integration of heteroatoms into the scaffold, , several structure–property relationships have been drawn for substituent group placement on the PN-heterocycle scaffold, which include both the phenyl group on the phosphorus as well as the substituents at the 3- and 6-positions, , thus guiding the development of the fluorophores in this study ( vide infra ). Moreover, most of the PN-systems are compatible with Lipinski’s “Rule of Five”, as they have <5 hydrogen bond donors, <10 hydrogen bond acceptors, a mass <500 amu, and a low octanol–water partition coeffient, suggesting that this class of compounds may be cell permeable.…”