Why do five-membered heterocyclic compounds sometimes not participate in polar Diels-Alder reactions?

Luis R. Domingo, Patricia Pérez, Daniela E. Ortega

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

The reactions of bicyclic enone (BCE, 1) with cyclopentadiene (Cp, 2) and the five-membered heterocyclic compounds (FHCs) furan 3 and N-methyl pyrrole 4 for the construction of polycyclic heterocyclic compounds have been studied at the B3LYP/6-31G* level. No reaction takes place in the absence of Lewis acid (LA) catalysts as a consequence of the high activation energy associated with these reactions. Electrophilic activation of BCE 1 by formation of a complex with the BF3 LA, 1-BF3, and solvent effects favor the reactions. However, a different reactivity is manifested by Cp 2 and FHCs 3 and 4. Thus, while the reaction of 1-BF3 with Cp 2 yields the expected exo [4 + 2] cycloadduct, the reactions of these FHCs yield Michael adducts. In any case, the reactions are characterized by the nucleophilic/electrophilic interaction between the most nucleophilic centers of these dienes and the most electrophilic center of complex 1-BF3. The greater ability of FHCs 3 and 4 to stabilize positive charges opposed to Cp 2 favors a stepwise mechanism with formation of a zwitterionic intermediate. Although in most stepwise Diels-Alder reactions, the subsequent ring closure has unappreciable barriers, in these FHCs the abstraction of a proton with regeneration of the aromatic ring becomes competitive. Thermodynamic calculations suggest that the exergonic character of the formation of the Michael adducts could be the driving force for the reactions involving FHCs.

Original languageEnglish
Pages (from-to)2462-2471
Number of pages10
JournalJournal of Organic Chemistry
Volume78
Issue number6
DOIs
Publication statusPublished - 15 Mar 2013

Fingerprint

Heterocyclic Compounds
Lewis Acids
Cyclopentanes
Pyrroles
Protons
Activation energy
Chemical activation
Thermodynamics
Catalysts

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

@article{dd324b72885a4b0e989900118c2412ff,
title = "Why do five-membered heterocyclic compounds sometimes not participate in polar Diels-Alder reactions?",
abstract = "The reactions of bicyclic enone (BCE, 1) with cyclopentadiene (Cp, 2) and the five-membered heterocyclic compounds (FHCs) furan 3 and N-methyl pyrrole 4 for the construction of polycyclic heterocyclic compounds have been studied at the B3LYP/6-31G* level. No reaction takes place in the absence of Lewis acid (LA) catalysts as a consequence of the high activation energy associated with these reactions. Electrophilic activation of BCE 1 by formation of a complex with the BF3 LA, 1-BF3, and solvent effects favor the reactions. However, a different reactivity is manifested by Cp 2 and FHCs 3 and 4. Thus, while the reaction of 1-BF3 with Cp 2 yields the expected exo [4 + 2] cycloadduct, the reactions of these FHCs yield Michael adducts. In any case, the reactions are characterized by the nucleophilic/electrophilic interaction between the most nucleophilic centers of these dienes and the most electrophilic center of complex 1-BF3. The greater ability of FHCs 3 and 4 to stabilize positive charges opposed to Cp 2 favors a stepwise mechanism with formation of a zwitterionic intermediate. Although in most stepwise Diels-Alder reactions, the subsequent ring closure has unappreciable barriers, in these FHCs the abstraction of a proton with regeneration of the aromatic ring becomes competitive. Thermodynamic calculations suggest that the exergonic character of the formation of the Michael adducts could be the driving force for the reactions involving FHCs.",
author = "Domingo, {Luis R.} and Patricia P{\'e}rez and Ortega, {Daniela E.}",
year = "2013",
month = "3",
day = "15",
doi = "10.1021/jo3027017",
language = "English",
volume = "78",
pages = "2462--2471",
journal = "Journal of Organic Chemistry",
issn = "0022-3263",
publisher = "American Chemical Society",
number = "6",

}

Why do five-membered heterocyclic compounds sometimes not participate in polar Diels-Alder reactions? / Domingo, Luis R.; Pérez, Patricia; Ortega, Daniela E.

In: Journal of Organic Chemistry, Vol. 78, No. 6, 15.03.2013, p. 2462-2471.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Why do five-membered heterocyclic compounds sometimes not participate in polar Diels-Alder reactions?

AU - Domingo, Luis R.

AU - Pérez, Patricia

AU - Ortega, Daniela E.

PY - 2013/3/15

Y1 - 2013/3/15

N2 - The reactions of bicyclic enone (BCE, 1) with cyclopentadiene (Cp, 2) and the five-membered heterocyclic compounds (FHCs) furan 3 and N-methyl pyrrole 4 for the construction of polycyclic heterocyclic compounds have been studied at the B3LYP/6-31G* level. No reaction takes place in the absence of Lewis acid (LA) catalysts as a consequence of the high activation energy associated with these reactions. Electrophilic activation of BCE 1 by formation of a complex with the BF3 LA, 1-BF3, and solvent effects favor the reactions. However, a different reactivity is manifested by Cp 2 and FHCs 3 and 4. Thus, while the reaction of 1-BF3 with Cp 2 yields the expected exo [4 + 2] cycloadduct, the reactions of these FHCs yield Michael adducts. In any case, the reactions are characterized by the nucleophilic/electrophilic interaction between the most nucleophilic centers of these dienes and the most electrophilic center of complex 1-BF3. The greater ability of FHCs 3 and 4 to stabilize positive charges opposed to Cp 2 favors a stepwise mechanism with formation of a zwitterionic intermediate. Although in most stepwise Diels-Alder reactions, the subsequent ring closure has unappreciable barriers, in these FHCs the abstraction of a proton with regeneration of the aromatic ring becomes competitive. Thermodynamic calculations suggest that the exergonic character of the formation of the Michael adducts could be the driving force for the reactions involving FHCs.

AB - The reactions of bicyclic enone (BCE, 1) with cyclopentadiene (Cp, 2) and the five-membered heterocyclic compounds (FHCs) furan 3 and N-methyl pyrrole 4 for the construction of polycyclic heterocyclic compounds have been studied at the B3LYP/6-31G* level. No reaction takes place in the absence of Lewis acid (LA) catalysts as a consequence of the high activation energy associated with these reactions. Electrophilic activation of BCE 1 by formation of a complex with the BF3 LA, 1-BF3, and solvent effects favor the reactions. However, a different reactivity is manifested by Cp 2 and FHCs 3 and 4. Thus, while the reaction of 1-BF3 with Cp 2 yields the expected exo [4 + 2] cycloadduct, the reactions of these FHCs yield Michael adducts. In any case, the reactions are characterized by the nucleophilic/electrophilic interaction between the most nucleophilic centers of these dienes and the most electrophilic center of complex 1-BF3. The greater ability of FHCs 3 and 4 to stabilize positive charges opposed to Cp 2 favors a stepwise mechanism with formation of a zwitterionic intermediate. Although in most stepwise Diels-Alder reactions, the subsequent ring closure has unappreciable barriers, in these FHCs the abstraction of a proton with regeneration of the aromatic ring becomes competitive. Thermodynamic calculations suggest that the exergonic character of the formation of the Michael adducts could be the driving force for the reactions involving FHCs.

UR - http://www.scopus.com/inward/record.url?scp=84875163993&partnerID=8YFLogxK

U2 - 10.1021/jo3027017

DO - 10.1021/jo3027017

M3 - Article

C2 - 23350936

AN - SCOPUS:84875163993

VL - 78

SP - 2462

EP - 2471

JO - Journal of Organic Chemistry

JF - Journal of Organic Chemistry

SN - 0022-3263

IS - 6

ER -