The Advances and Applications of Arynes and Their Precursors to Synthesize the Heterocyclic Compounds: A Review

Alam, Md. Ashraful

doi:10.11648/j.ajhc.20170305.11

Cited by 5 publications

(2 citation statements)

References 24 publications

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“…One of such areas includes bonding of transition metals with arynes since arynes are undoubtedly extremely reactive species, even at very low temperatures. Out of aryne systems, benzyne (1,2-didehydrobenzene) is the most widely studied, whose transient existence was initially confirmed through pioneering investigations conducted by Wittig and Roberts in the 1950s. Benzyne’s unique reactivity arises from this strained triple bond (the most common representation of benzyne, Figure ), and the generation of benzyne involves the 1,2-elimination of leaving groups from corresponding precursor, leading to its versatile reactivity toward nucleophiles and electrophiles, facilitating the construction of complex organic compounds.…”

Section: Introductionmentioning

confidence: 99%

Unveiling the Bonding Scenario in Metal–Aryne Complexes with EDA-NOCV Analyses

Suthar,

Mondal

2024

Organometallics

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Transition metal-based organometallic compounds have been explained by the Dewar−Chatt−Duncanson (DCD) model, established in 1953, which provides a conceptual framework elucidating the interaction between transition metals and ligands. This interaction involves σ-donation from the ligand to the symmetric vacant d-orbital of the transition metal (TM ⃖ L), coupled with πbackdonation from a distinctly occupied d-orbital of the transition metal to the suitable empty orbital (mostly antibonding type) on the ligand (TM → L), which leads to the variations in bond lengths in the bonded ligand (typically bond elongation) and vibrational frequencies within ligand bonds (such as C=O, N=N, and C=C of olefins), serving as an indicator of the ligand's π-accepting strength. One such effective and highly reactive ligand is benzyne/aryne, which is generated in situ and has been stabilized by coordinating to a transition metal. The transition metal−aryne complexes are primarily formed with low-valent early transition metals and late (d 10 ) transition metals. The findings, on employing the EDA-NOCV calculations of different classical textbook examples of experimentally synthesized mononuclear TM−aryne complexes, specifically TM−benzyne complexes, reveal intriguing deviations from the original DCD model and suggest that the bonding interaction of these well-known organometallic complexes occurs between TM and aryne fragments in their 'electronically charged doublet states' (as TM + and aryne − ). Notably, when the TM resides within groups IV−IX of the periodic table, the interaction exhibits one dative σ-bond, one electron-sharing π-bond, and one (a few have two) additional dative σ/π bond (D + E). Even though late TM (d 10 , Ni/Pd/Pt) exhibits the potential to form both dative bonds (D) (in accordance with the DCD model) and D + E interaction between electronically charged fragments, it still slightly favors the later bonding scenario. The major contribution in the bond formation of TM−aryne complexes is from electrostatic interaction energy (ΔE elstat ) and the major contribution toward the orbital interaction (ΔE orb ) is dominated by the electron sharing π-bond formation.

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Section: Introductionmentioning

confidence: 99%

Unveiling the Bonding Scenario in Metal–Aryne Complexes with EDA-NOCV Analyses

Suthar,

Mondal

2024

Organometallics

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“…σ-Type carbon-centered aromatic biradicals, including the three benzynes (ortho-, meta-, and para-) and their analogues, have been studied for decades for their potential application in various fields, including organic synthesis and anticancer therapeutics. − Because of the difficulty in clean and simultaneous generation of two radical sites that are not adjacent to each other in solution, mass spectrometers have been used to study numerous gas-phase aromatic biradicals with a chemically inert charged site. ,, These biradicals are generated from protonated diiodo- or iodonitro precursors by collision-activated dissociation to homolytically cleave off iodo atoms and/or nitro groups. In most cases, the charged site has been demonstrated to influence reactions like a strongly electron-withdrawing substituent, without directly participating in the reactions …”

Section: Introductionmentioning

confidence: 99%

Effects of the Distance between Radical Sites on the Reactivities of Aromatic Biradicals

Ding

Jiang

et al. 2020

J. Org. Chem.

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Coupling of the radical sites in isomeric benzynes is known to hinder their radical reactivity. In order to determine how far apart the radical sites must be for them not to interact, the gasphase reactivity of several isomeric protonated (iso)quinoline-and acridine-based biradicals was examined. All the (iso)quinoliniumbased biradicals were found to react slower than the related monoradicals with similar vertical electron affinities (i.e., similar polar effects). In sharp contrast, the acridinium-based biradicals, most with the radical sites farther apart than in the (iso)quinolinium-based systems, showed greater reactivities than the relevant monoradicals with similar vertical electron affinities. The greater distances between the two radical sites in these biradicals lead to very little or no spin−spin coupling, and no suppression of radical reactivity was observed. Therefore, the radical sites can still interact if they are located on adjacent benzene rings and only after being separated further than that does no coupling occur. The most reactive radical site of each biradical was experimentally determined to be the one predicted to be more reactive based on the monoradical reactivity data. Therefore, the calculated vertical electron affinities of relevant monoradicals can be used to predict which radical site is most reactive in the biradicals.

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