The organic chemistry of phospholes

Abstract

Contents Introduction 429 I. Synthetic Problems 430 A. Building the 1W-Phosphole Ring 430 B. 2Hand 3H-Phospholes and the 1H-432 2H-Phosphoie Equilibrium C. Synthesis of the Phospholyl Anions 434 II. Physicochemical Data and Theoretical 435 Problems A. 1H-Phospholes 435 1. Structural Data 435 2. Spectroscopic Data 435 3. The Aromaticity Problem 437 B. Phospholyl Anions 438 NMR Data and Theoretical Calculations 438 III. Chemical Properties 439 A. 1H-Phospholes 439 1. Nucleophilic Properties of Phosphorus 439 2. Electrophilic Properties of Phosphorus 440 3. Heatand UV-Induced Transformations 440 4. Diels-Alder Reactivity of the Dienic 441 System 5. Other Reactions of the Dienic System 444 6. Ring Opening 445 7. Ring Expansions 446 B. 2H-Phospholes 447 Dimerization and Reactivity toward A-H 447 Compounds, Dienes, and Dienophiles C. Phospholyl Anions 448 Nucleophilic Properties of Phosphorus 448 IV. Phospholes as Synthons 449 A. Synthesis of Other Phosphorus 449 Heterocycles B. Uses In Synthetic Organic Chemistry and in 450 Homogeneous Catalysis

Synthesis, Characterization and Theoretical Calculations of Novel Five Membered Rings Containing Phosphorus and Arsenic Atoms

“…The mixture containing both rings 3 and 4, which was obtained from SiMe 3 Figure 2. The reaction of BrCH(SiMe 3 ) 2 with the anionic ring 3 may generate two isomers 5 and 7 (route A in Figure 2). The former is obtained through the bonding of the R group to the phosphorus atom and in the later, the R group bonds to the arsenic atom.…”

“…Phosphole (Figure 1), is known to be a nonplanar, nonaromatic molecule. [2][3][4][5] This behavior is attributed to the pyramidal character at phosphorus. 6 This class of compounds is of particular interest in coordination chemistry due to its ability to act in several different coordination modes.…”

“…All these coordination modes have been reviewed in the literature. [2][3][4] Theoretical calculations [7][8][9] have shown that increasing the number of phosphorus atoms in the ring structure of phosphole leads to a decrease in the pyramidal character of the sp 3 phosphorus, giving rise to a planar phosphole structure. These calculations also showed that the ring planarity is directly related to the electronic delocalization (or aromaticity) and a planar ring is predicted to be strongly aromatic by means of theoretical calculations.…”

“…The synthesis of two new arsadiphospholes of formula (AsP 2 C 2 Bu t 2 )CH(SiMe 3 ) 2 , from 4-arsa-1,2-diphosphacyclopentadienyl and 2-arsa-1,4-diphosphacyclopentadienyl ring anions are reported together with their characterization by 31 P NMR. Ab initio calculations at the MP2/6-31G(d) level of theory were carried out to investigate the energy barrier for pyramidal inversion about the pyramidal P and As atoms, relative stability and aromaticity character of all possible isomers in the gas phase.…”

Phosphorus‐Containing Polycyclic Aromatic Hydrocarbons

“…[37] Furthermore, the diversity of conjugated P-heterocycles (three-membered phosphirenes, [38] four-membered phosphetes, [39] five-membered phospholes, [40] six-membered phosphinines, [41] seven-membered phosphepines), [42] -P), make this heteroatom highly versatile and adept to the tuning of the physicalproperties of p systemsand PAHs, in particular.…”