Theoretical explanation of the regioselectivity of polar cycloaddition reactions between furan derivatives and Danishefsky’s diene

The Stepwise Diels–Alder Reaction of 4‐Nitrobenzodifuroxan with Danishefsky’s Diene

“…[36] Assuming that the Curtin-Hammett principle is not operating in the present system and, thus, conformer 12 c is the most reactive structure with the cis arrangement required for reactions to take place with some concerted character, we first focused our DFT analysis of the NBDF/cis-12 interaction to pathways that correspond to the involvement of this structure.…”

Comprehensive DFT Study on Site‐, Regio‐, and Stereoselectivity of Diels–Alder Reactions Leading to 5‐Hydroxybenzofurans

“…DFT-based descriptors [a] for the reactive sites of the reactants. [6] Dienophile ω k Diene N k 1a 1b 1c Channels 3Ј and 4Ј deserve special attention: in several cases for these two channels -1c + 2 and the exo addition mode for 1a + 2 -two-step mechanisms involving true intermediates were obtained by the calculations (Figure 2). In contrast, the 1b + 2 cycloaddition in these two channels should also proceed through a concerted mechanism.…”

“…Possible explanations for the preferred formation of the bond to C4Ј of the diene are: 1) strong interaction between the reactant active sites due to a greater overlap of the orbitals [i.e., the interaction between the most electrophilic site of the dienophile (C3) and the most nucleophilic site of the diene [6] (C4Ј, see below, Table 3) leads to a stronger bonding], and 2) increased steric interactions between the oxygen substituent at C1Ј of the diene and the dienophile's reaction center (C2 for channels 1 and 2). On the other hand, the substituent at the 3-position of the diene lies too far away from the reaction center and does not interfere with the approaching furan sterically in a significant way in any of the TSs.…”

“…[5] For the reactions shown in Scheme 1, for instance, we demonstrated that the local electrophilicity (ω k ) and nucleophilicity (N k ) can be used to explain the observed regioselectivity. [6] More recently we studied the regio-and stereoselectivity of the same series of DA reactions using some global reac- and stereochemistry were analyzed in detail. Moreover, the extrusion of nitrous acid from the Diels-Alder cycloadducts and the formation of the aromatic products were also explained in order to give a total description of the complete domino processes.…”

Ionic Liquids in Polar Diels-Alder Reactions Using Carbocycles and Heterocycles as Dienophiles

“…We can assume that high nucleophilicity and high electrophilicity corresponds to opposite extremes of this scale. Brasca, et al, 2009). In the table we also included some global properties such as the chemical potential and the chemical hardness.…”