Phosphinine – synthesis of a heavy sibling of pyridine (microreview)

Tokarz, Paweł; Zagórski, Piotr M.

doi:10.1007/s10593-017-2138-1

Cited by 11 publications

(5 citation statements)

References 20 publications

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“…To meet these criteria, we have chosen the radicals 2 , 8 , 12 , and 21 for further studies. Indeed, all of these radicals have remarkable RSE values, and the precursors to these radicals, namely, phosphirenes, phospholes, − phosphinines , (phosphabenzenes), and phosphepins, can be synthesized using well-established and effective techniques.…”

Section: Resultsmentioning

confidence: 99%

Stability of Carbocyclic Phosphinyl Radicals: Effect of Ring Size, Delocalization, and Sterics

2022

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In this computational study, we report on the stability of cyclic phosphinyl radicals with an aim for a systematical assessment of stabilization effects. The radical stabilization energies (RSEs) were calculated using isodesmic reactions for a large number of carbocyclic radicals possessing different ring sizes and grades of unsaturation. In general, the RSE values range from −1.2 to −14.0 kcal·mol–1, and they show practically no correlation with the spin populations at the P-centers. The RSE values correlate with the reaction Gibbs free energies calculated for the dimerization of the studied simple radicals. Therefore, the more easily accessible RSE values offer a cost-effective estimation of global stability in a straightforward manner. To explore the effect of unsaturation on the RSE values, delocalization energies were determined using appropriate isodesmic reactions. Introducing unsaturations beside the P-center into the backbone of the rings leads to an additive increase in the magnitude of the delocalization energy (∼10, 20, and 30 kcal·mol–1, respectively, for radicals with one, two, and three CC bonds in the conjugation). Parallelly, the spin populations at the P-centers also dwindle gradually by ∼0.1 e in the same order, indicating that the lone electron delocalizes over the π-system. Radicals containing exocyclic CC π-bonds were also investigated, and all of these radicals have rather similar stabilities independently of the ring size, outlining the primary importance of the two exocyclic π-bonds in the conjugation. Among the radicals involved in our study, those with the best electronic stabilization are the unsaturated three-, five-, six-, and seven-membered rings containing the maximum number of conjugated vinyl fragments. The largest delocalization energy of 31.5 kcal·mol–1 and the lowest obtained spin population of 0.665 e were found for the fully unsaturated seven-membered radical (phosphepin derivative). Importantly, the electronic stabilization effects alone are insufficient for stabilizing the radicals in monomeric forms epitomized by the exothermic dimerization energies (−40 to −58 kcal·mol–1). Therefore, it is essential to apply sterically demanding bulky substituents on the α-C-atoms. Tweaking the steric congestion enabled us to propose radicals that are expected to be stable against dimerization and, consequently, may be realistic target species for synthetic investigations. The effects contributing to the stability of radicals having sterically encumbered substituents have also been explored.

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Section: Resultsmentioning

confidence: 99%

Stability of Carbocyclic Phosphinyl Radicals: Effect of Ring Size, Delocalization, and Sterics

2022

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Section: Introductionmentioning

confidence: 99%

“…We believe this is because of the high relative reactivity of the phosphinine P‐atom, which renders phosphinine incompatible with most polymerization protocols. For λ 3 ‐phosphinine, the typical electrophilic attack or nucleophilic attack is more preferred at the P atom . λ 5 ‐Phosphinine is more stable owing to the absence of phosphorus lone pairs, but some strong acids or bases can still attack the P atom during some polymerizations .…”

Section: Introductionmentioning

confidence: 99%

“…For l 3 -phosphinine, the typical electrophilic attack or nucleophilic attack is more preferred at the Pa tom. [30] l 5 -Phosphinine is more stable owing to the absence of phosphorus lone pairs, but some stronga cids or bases can still attack the Pa tom during some polymerizations. [25a] Therefore, stable phosphinine-based monomers and mild polymerization routes need to be carefully chosen to achieve P-containing p-conjugated frameworks.…”

Section: Introductionmentioning

confidence: 99%

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A π‐Conjugated, Covalent Phosphinine Framework

Huang

Tarábek

Kulkarni

et al. 2019

Chemistry A European J

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Structural modularity of polymer frameworks is a key advantage of covalent organic polymers, however, only C, N, O, Si, and S have found their way into their building blocks so far. Here, the toolbox available to polymer and materials chemists is expanded by one additional nonmetal, phosphorus. Starting with a building block that contains a λ5‐phosphinine (C5P) moiety, a number of polymerization protocols are evaluated, finally obtaining a π‐conjugated, covalent phosphinine‐based framework (CPF‐1) through Suzuki–Miyaura coupling. CPF‐1 is a weakly porous polymer glass (72.4 m2 g−1 BET at 77 K) with green fluorescence (λmax=546 nm) and extremely high thermal stability. The polymer catalyzes hydrogen evolution from water under UV and visible light irradiation without the need for additional co‐catalyst at a rate of 33.3 μmol h−1 g−1. These results demonstrate for the first time the incorporation of the phosphinine motif into a complex polymer framework. Phosphinine‐based frameworks show promising electronic and optical properties, which might spark future interest in their applications in light‐emitting devices and heterogeneous catalysis.

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“…Several synthetic routes to simple phosphinines have been described. − However, there are certain synthetic limitations hindering easy adaptation to helicene chemistry. Furthermore, the stability of the phosphinine core is closely related to its substitution pattern, preventing the preparation of large libraries of such compounds .…”

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confidence: 99%

Synthesis of 2-Phospha[7]helicene, a Helicene with a Terminal Phosphinine Ring

et al. 2022

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A synthetic strategy toward phosphahelicenes containing a terminal phosphinine ring has been explored. The 4-phenyl-6-methyl-2-phospha[7]helicene was prepared from starting 2-bromobenzo[c]phenanthrene in 12% overall yield in 12 steps. The synthetic approach involves introduction of the phosphorus function prior to photocyclization forming the final helicene skeleton, followed by the formation of a phosphorus hexacycle. The structure of the first phosphahelicene with a terminal phosphinine ring was confirmed by X-ray crystallography.The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.orglett.2c01723.Synthetic details, Experimental procedures, 1 H, 13 C and 31 P NMR spectra, characterization data for all new compounds, HPLC analysis, computational data, UV− vis, CD and crystallographic data (PDF) FAIR data, including the primary NMR FID files, for compounds 1

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Phosphinine – synthesis of a heavy sibling of pyridine (microreview)

Cited by 11 publications

References 20 publications

Stability of Carbocyclic Phosphinyl Radicals: Effect of Ring Size, Delocalization, and Sterics

Stability of Carbocyclic Phosphinyl Radicals: Effect of Ring Size, Delocalization, and Sterics

A π‐Conjugated, Covalent Phosphinine Framework

Synthesis of 2-Phospha[7]helicene, a Helicene with a Terminal Phosphinine Ring

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