Abstract
The structure and the contribution of the bis(2-chloroethyl) 2-nitro 1a and 2-bromo-2-nitroethenylphosphonates 1b with anthracene 2 in the Diels–Alder (DA) reactions have been studied within the Molecular Electron Density Theory (MEDT) at the B3LYP functional together with 6-31G(d), 6-31+G(d) and 6-31+G(d,p) basic sets. Analysis of the Conceptual Density Functional Theory (CDFT) reactivity indices indicates that 1a and 1b can be classified as a strong electrophile and marginal nucleophile, while 2 is classified as a strong electrophile and strong nucleophile. The studied DA reactions take place through a one-step mechanism. A Bonding Evolution Theory (BET) of the one path associated with the DA reaction of 1a with 2 indicates that it is associated with non-concerted two-stage one-step mechanism. BET analysis shows that the first C2-C3 single bond is formed in Phase VI, while the second C1-C6 single bond is formed in the Phase VIII. The formation of both single bonds occurs through the merging of two C2 and C3, C1 and C6 pseudoradical centers, respectively.
Highlights
The Diels–Alder (DA) reaction is among the most formidable available protocols for the construction of optically active compounds, with extensive synthetic applications in natural products with a large range of biological activity [1,2,3,4]
Many studies concerning of the DA reactions put these reactions in a completely different light; a one-step mechanism has been replaced by a two-step mechanism undergoing through the intermediate
It was found that the reaction of α-(trihaloethylidene)-nitroalkanes with push–pull enamines affords one to cycloadduct or linear enamines depending on the nature of the trihalomethyl group
Summary
The Diels–Alder (DA) reaction is among the most formidable available protocols for the construction of optically active compounds, with extensive synthetic applications in natural products with a large range of biological activity [1,2,3,4]. 1-methylpyrrole and dimethyl acetylenedicarboxylate two alternative reaction pathways have been considered This reaction proceeds with a two-step formation of cycloadduct, and intramolecular proton transfer affords a Michael adduct (Scheme 3). Observed course of reaction between α-(trihaloethylidene)-nitroalkanes been considered This reaction proceeds with a two-step formation of cycloadduct, and with push–pull enamines [7]. In the case of the experimental [8] and theoretical [9] research of the reaction between 1methylpyrrole and dimethyl acetylenedicarboxylate two alternative reaction pathways have been considered.
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