Quantum chemical study on the mechanism and selectivity of [3 + 2] cycloaddition reactions of aryl nitrile oxides with furanone

The norbornadiene (NBD) molecule, C7H8, owes its fame to its remarkable photoswitching properties that are promising for molecular solar-thermal energy storage systems. Besides this photochemical interest, NBD is a rather unreactive species within astrophysical conditions and it should exhibit high photostability, properties that might also position this molecule as an important constituent of the interstellar medium (ISM)-especially in environments that are well shielded from short-wavelength radiation, such as dense molecular clouds. It is thus conceivable that, once formed, NBD can survive in dense molecular clouds and act as a carbon sink. Following the recent interstellar detections of large hydrocarbons, including several cyano-containing ones, in the dense molecular cloud TMC-1, it is thus logical to consider searching for NBD-which presents a shallow but non-zero permanent electric dipole moment (0.06 D)-as well as for its mono- and dicyano-substituted compounds, referred to as CN-NBD and DCN-NBD, respectively. The pure rotational spectra of NBD, CN-NBD, and DCN-NBD have been measured at 300 K in the 75-110 GHz range using a chirped-pulse Fourier-transform millimetre-wave spectrometer. Of the three species, only NBD was previously studied at high resolution in the microwave domain. From the present measurements, the derived spectroscopic constants enable prediction of the spectra of all three species at various rotational temperatures (up to 300 K) in the spectral range mapped at high resolution by current radio observatories. Unsuccessful searches for these molecules were conducted toward TMC-1 using the QUIJOTE survey, carried out at the Yebes telescope, allowing derivation of the upper limits to the column densities of 1.6 × 1014 cm-2, 4.9 × 1010 cm-2, and 2.9 × 1010 cm-2 for NBD, CN-NBD, and DCN-NBD, respectively. Using CN-NBD and cyano-indene as proxies for the corresponding bare hydrocarbons, this indicates that-if present in TMC-1-NBD would be at least four times less abundant than indene.

https://pubs.rsc.org/en/content/articlepdf/2023/fd/d3fd00016h

Searches for bridged bicyclic molecules in space-norbornadiene and its cyano derivatives.

• 1. A novel family of superalkalis cationic clusters (ONa4-X)+, (NNa5-X)+, (CNa6-X)+ and (BNa7- X)+ (where X= F, Cl, Br) have been identified. • 2. These (M−X)+ clusters have lower ionization potential (3.61–4.28 eV) • 3. Na can generate superalkali cations when doped with halogens. • 4. Fluorination is more effective in forming superalkalis than chlorination and bromination. • 5. The identified superalkalis have high stability and the strong M-X interactions. Superalkalis are chemical species with lower ionization energy than those of alkali-metal atoms. Superalkali cationic clusters (ONa 4 -X) + , (NNa 5 -X) + , (CNa 6 -X) + and (BNa 7 -X) + (where X= F, Cl, Br) with low vertical electron affinities (VEA) have been identified. The study revealed that alkali metal, Na can generate superalkali cations when doped with halogens. These (M−X) + clusters have lower VEA (3.61–4.28 eV) at the CCSD/6-311++G(2d,2p) level. Fluorination is more effective in forming superalkalis. The stability of the studied cations is guaranteed by their strong M-X interactions. The proposed superalkalis clusters can act like efficient reducing agents in material syntheses and chemical processes. 

Halogenation Lowers the Electron Affinity: A Novel Approach to Design Superalkali Cationic Clusters

The [3 + 2] cycloaddition (32CA) reaction of benzonitrile oxide (BNO) with 4-substituted 4-hydroxy-2-cyclopentenone has been investigated using molecular electron density theory (MEDT) at the Density Functional Theory (DFT) B3LYP/6-31G (d), M06/6-311G (d,p) and M06-2X/6–311++G (d,p) levels. The present theoretical computations indicate that the reaction of BNO with 4-substituted 4-hydroxy-2-cyclopentenones is via [3 + 2] cycloaddition, where the three atom component (TAC) chemo-selectively adds across the alkene functionality in the 2-cyclopentenones (Path A). Analysis of the electrophilic PA+ and nucleophilic PA− Parr functions at the different reaction sites in the alkene counterpart indicates that the aryl nitrile oxides add across the atomic centers with the highest Mulliken atomic spin densities. The results reported in this study are in good agreement with previous experimental work. The GEDT calculations unravel the low polar character of the [3 + 2] cycloaddition reactions. This reaction occurs with poor enantioselectivity, but a high degree of stereo-, peri-, diastereo, and regioselectivity is seen for the reaction of the BNO with 4-hydroxy-4-methyl-2-cyclopentenones. The regioselectivity of the reactions is the same in all the solvents investigated. 

Quantum Mechanical Elucidation on [3+2] cycloaddition reaction of aryl nitrile oxide with cyclopentenones.

[3 + 2] Cycloaddition Reaction of Disubstituted-3-Benzylidene Succinimide with C, N-Disubstituted Nitrile Imines for Synthesizing Spiro-heterocycles: A Computational Study

Regio-, stereo-, and site-selectivities of 1,3-dipolar Cycloaddition reaction of benzonitrile oxide with unsymmetrically substituted norbornenes and norbornadienes: A computational study

Harun Abdullah

Papers

Regio-, stereo-, and site-selectivities of 1,3-dipolar Cycloaddition reaction of benzonitrile oxide with unsymmetrically substituted norbornenes and norbornadienes: A computational study

Quantum chemical study on the mechanism and selectivity of [3 + 2] cycloaddition reactions of aryl nitrile oxides with furanone

Quantum Mechanical Elucidation on [3+2] cycloaddition reaction of aryl nitrile oxide with cyclopentenones.