Nitrous Oxide as a 1,3-Dipole:  A Theoretical Study of Its Cycloaddition Mechanism

Abstract

The 1,3-dipolar cycloadditions of nitrous oxide and substituted alkynes have been studied at the B3LYP/6-31G(d,p) level. The reaction is controlled by LUMO (dipole)--HOMO (dipolarofile) and involves aromatic transition structures. The shape of the potential energy surface and the regioselectivity are not affected by the polarity of the solvents, except in the case of N2O + HC triple bond CSiH3. Different reactivity criteria including FMO coefficients product C, local softness differences Delta, magnetic susceptibility anisotropy chi(anis), and nucleus-independent chemical shifts NICS were used to predict the regioselectivity in all studied cases; the C, Delta criteria turn out to give the best results among them. The aromaticity of the transition structure is not a factor in determining the regiochemistry of the cycloaddtition reactions.

5-(3-Phosphonated 1H-1,2,3-triazol-4-yl)isoxazolidines: synthesis, DFT studies and biological properties

“…Moreover, the electrophilicity differences between vinyl-triazole and nitrone (∆ω < 0.2 eV) indicate a lower polar character for these cycloadditions, and their values are characteristic of nonpolar pericyclic reactions. [38][39] Being the present 1,3-dipolar cycloaddition an inverse electron demand type process, the nitrone undergoes a nucleophilic attack by the vinyl-triazole; thus, the local properties to be used are reported in Table 3. For the dipolarophile, C4 has the higher local nucleophilicity index, ω-with respect to C5.…”

Theoretical investigation of the interaction of glycerol with aluminum and magnesium phthalocyanines

“…In order to seek a possible explanation for these complexation phenomena we have also calculated the Fukui functions and applied the theory of hard-and-soft acid-base (HSAB) in the reactants. The statement that "soft likes soft" and "hard likes hard", together with the idea that the larger the value of the Fukui function, the greater the reactivity, also provides a very useful approach to explain the chemical reactivity of many chemical systems [51][52][53][54][55][56][57]. The determination of the specific sites at which the interaction between two chemical species takes place is very important to elucidate the path and the products of a given reaction.…”

Use of Local Softness for the Interpretation of Reaction Mechanisms

“…For example, 1,3-dipolar cycloaddition reactions between various dipoles and dipolarophiles [30][31][32], excited state cycloadditions [33], and [4+2] Diels-Alder reactions [34] were studied recently by using local reactivity descriptors. However, in order to explain the regiochemistry of a multicenter reaction, such as cycloaddition, apart from the local softness one also needs to consider HSAB principle in a local sense.…”