An experimental and theoretical study of the hetero Diels–Alder reactions between (E)-2-aryl-1-cyano-1-nitroethenes and ethyl vinyl ether: one-step or zwitterionic, two-step mechanism?

Abstract

The mechanistic aspects of the hetero Diels-Alder reactions between strongly electrophilic (E)-2-aryl-1-cyano-1-nitroethenes and ethyl vinyl ether have been analyzed on the basis of kinetic experimental results as well as quantum chemical simulations of reaction paths. These reactions may theoretically proceed via one step or stepwise, zwitterionic mechanism. It was found that the conversion of addends into adducts carried out via polar, but not zwitterionic mechanism. This is confirmed by kinetic substituent and solvent effects. Subsequently, a detailed analysis of internal reaction coordinate trajectories shows that the title reactions should be considered as examples of ''two-stage one-step'' cycloadditions according to Domingo terminology.

Understanding the mechanism of the decomposition reaction of nitroethyl benzoate through the Molecular Electron Density Theory

“…They are useful compounds applied, e.g. in syntheses of many four-, fiveand six-membered compounds in cycloaddition reactions [6][7][8][9][10][11]. Applications of nitroalkenes in organic synthesis are largely due to their ease of conversion into a variety of functionalities.…”

A reexamination of the molecular mechanism of the Diels–Alder reaction between tetrafluoroethene and cyclopentadiene

“…The stationary points on reaction paths were localized in an analogous manner as in the case of the previously analyzed DA reaction of conjugated nitroalkenes with alkyl-vinyl ethers [29,30]. In particular, for the structure optimization of the reactants and the reaction products, the Berny algorithm [31] was applied.…”

Chemistry of 2-aryl-1-cyano-1-nitroethenes. Part II. Chemical transformations

“…The yields of nitronates (45a-d) were very high (75-90%) but a mixture of diastereoisomers was obtained (Table 12). The kinetic aspects of these transformations have also been recently discovered [9] In the same year, Pizzo et al [3] showed an example of intramolecular cycloaddition in 2-(2' -(3",3"-dimethyl)allyloxyphenyl)-1-cyano-1-nitroetene (46) generated in situ. This reaction led to the formation of cis-4a,10b,-dihydro- 1-cyano-4,4,dimethylbenzo[b]pyrene- [4,3-d] [1,2] oxazine-2-oxide (47) and its 4a-epimer (48) in a 16:1 ratio and with a 60% yield of (48).…”

“…The chemical transformations of these compounds include [2+3] cycloaddition to nitrogen-containing Three-Atoms-Components (TACs), which occupies an important place among the synthetic tools of organic chemistry [7]. Several examples of the participation of ACNs in Diels-Alder reactions as ethylenes as well as heterodienes are also known [3,8,9]. This paper is a continuation of our study on the chemistry of 2-aryl-1-cyano-1-nitroethenes.…”