Paving the Way to Novel Phosphorus‐Based Architectures: A Noncatalyzed Protocol to Access Six‐Membered Heterocycles

Abstract

Phosphorus-based heterocycles provide access to materials with properties that are inaccessible from all-carbon architectures. The unique hybridization of phosphorus gives rise to electron-accepting capacities, a large variety of coordination reactions, and the possibility of controlling the electronic properties through phosphorus postfunctionalization. Herein, we describe a new noncatalyzed synthetic protocol to prepare fused six-membered phosphorus heterocycles. In particular, we report the synthesis of novel phosphaphenalenes. These fused systems exhibit the benefits of both five- and six-membered phosphorus heterocycles and enable a series of versatile postfunctionalization reactions. This work thus opens up new horizons in the field of conjugated materials.

Intramolecular Phosphacyclization: Polyaromatic Phosphonium P‐Heterocycles with Wide‐Tuning Optical Properties

“…Because of this distortion, phosphacyclic motifs feature a boat‐like conformation, which is reminiscent to the configuration of a family of acridophosphine compounds, but it is not observed in the planar systems based on the naphthalene moiety . The C−P bond lengths in 1 c , 2 c , and 4 c are in the range 1.765(2)–1.796(1) Å; the observed parameters are typical for P heterocyclic compounds with λ 5 ‐σ 4 or λ 4 ‐σ 4 phosphorus centers, such as phosphole oxides, phospha‐fluorescein, and related derivatives including cyclic phosphonium salts …”

Dismantling the Hyperconjugation of π‐Conjugated Phosphorus Heterocycles

“…The changes in the hyperconjugation modes also impact the structural and optical properties of the phosphorus heterocycles. Analyzes of the X‐ray and computed geometries of compounds based on 1 / 2 , 3 / 4 , and 5 / 6 (Figure ) indicated that increasing the negative hyperconjugation implies, in all systems, a decrease in the θ βα P χ dihedral angle in order to increase the effective orbital overlap between the π‐system and the σ*‐exocyclic P bonds orbitals. This can be observed in compounds 2 , 4 and 6 , which present higher negative hyperconjugation, compared with their unoxidized counterparts 1 , 3 , and 5 .…”

Phosphorus‐Containing Polycyclic Aromatic Hydrocarbons

“…[65] In these systems, the phosphorusa tom retains its reactivity towardo xidants or transition metals.T he s 4 ,l 5 -P=Oc ompounds, such as 24 and 25,a re stable in air.T he polycyclic system is fully planar,a se videnced by the crystallographic structure of 25 ( Figure 14). Again, this is allowed by the positiono ft he phosphorus atom at the edge of the structure.…”

“…The contribution of the Po rbitals is larger (CCDC 1418421c ontains the supplementary crystallographic data for this paper.These data can be obtained free of charge from The Cambridge Crystallographic Data Centre.) [65] ChemPhysChem 2017, 18,2618 -2630 www.chemphyschem.org The authors furthere xtend their strategy with the preparation of highly distorted PAHf ragments featuring two heteroatoms (31-33;F igure 18). [67] Again, the presence of the tetrahedral Pa tom and the steric repulsion between the Me groups afford aP AH fragment composed of 13 cycles that can also be viewed as ad ouble [5]helicene, as shown on the crystallographic structure (Figure 18).…”