A DFT computational study on the molecular mechanism of reaction between pyridinium salts and π-deficient ethylenes: Why furan derivatives are formed instead of feasible cyclopropane derivatives and [3 + 2] cycloadducts?
Authors:
- Saeedreza Emamian,
- Radomir Jasiński
Abstract
The reaction between 1-(2-amino-2-oxoethyl)pyridinium ylide 4 ( PY4 ) and 1-methylene-3,4-dihydro naphthalen-2(1H)-one 5 ( MDN5 ) in the presence of acetonitrile (CH 3 CN) was theoretically studied at the M06-2X/6-31G(d,p) computational level. Calculated relative Gibbs free energies indicate that encounters between PY4 and MDN5 in the reaction mixture result in the formation of the highly zwitterionic betaine-like intermediate IM1ca in an entirely C1 A C5 regio- and a cisoid-anti stereoselective manner over the course of a Michael addition reaction through a very low barrier (4.2 kcal/mol) and a highly exergonic (24.7 kcal/mol) pathway. While C1 A C5 regioselectivity can be rationalized via the analysis of the computed nucleophilic and electrophilic Parr functions at the reactive sites of reagents, the cisoid-anti stereoselectivity predominance over the cisoid-syn one can nicely be portrayed within the non-covalent interactions (NCIs) analysis at the cisoid-anti transition state TS1ca and cisoid-syn transition state TS1cs involved in the Michael addition reaction. The electron-localization function (ELF) quantum topological analysis obviously demonstrates that the C1 carbon atom in PY4 exhibits a pseudoradical character indicating the high reactivity of PY4 toward C5 electrophilic attack of MDN5 which is characterized with a very low barrier associated with the C1 A C5 single bond formation along the Michael addition step. Upon formation of IM1ca , in excellent agreement with the experimental outcomes, an S N i-like reaction converts IM1ca into trans -furan derivative 8 together with pyridine via a high barrier (23.9 kcal/mol) but a highly irreversible pathway making compound 8 as the only reachable product under ‘‘thermodyna mically-controlled” conditions (refluxing over 8 h). In other words, neither [3 + 2] cycloadduct 6 (as the kinetically most favourable but thermodynamically most unfavourable product) nor cyclopropane derivative 7 (as both kinetically and thermodynamically most undesirable product) can be obtained under the reaction conditions. From the molecular mechanism point of view, the ELF analyses indicate that while C1 A C5 single bond formation within the Michael addition reaction takes place via aC-toC coupling of two pseudoradical C1 and C5 centers, formation of C1 A O8 single bond accompanied with the C1 A N15 single bond breaking at the generated IM1ca to afford compound 8 is a direct consequence of donation of some electron density of O8 oxygen lone electron pairs to the C1 carbon atom.
- Record ID
- CUT91deff59fae047ee969561a936d2d978
- Publication categories
- ;
- Author
- Journal series
- Computational and Theoretical Chemistry, ISSN 2210-271X, e-ISSN 1872-7999
- Issue year
- 2017
- Vol
- 1114
- Pages
- 87-100
- Other elements of collation
- schem.; tab.; wykr.; Bibliografia (na s.) - 99-100; Bibliografia (liczba pozycji) - 53; Oznaczenie streszczenia - Abstr.; Numeracja w czasopiśmie - Vol. 1114
- Keywords in English
- cycloaddition, DFT study, pyridinium salt, kinetically- and thermodynamically-controlled conditions, regio- and stereoselectivity, non-covalent interactions analysis, parr functions, ELF quantum topological analysis
- DOI
- DOI:10.1016/j.comptc.2017.05.019 Opening in a new tab
- URL
- http://www.sciencedirect.com/science/article/pii/S2210271X1730244X Opening in a new tab
- Language
- eng (en) English
- Score (nominal)
- 20
- Additional fields
- Indeksowana w: Web of Science, Scopus
- Uniform Resource Identifier
- https://cris.pk.edu.pl/info/article/CUT91deff59fae047ee969561a936d2d978/
- URN
urn:pkr-prod:CUT91deff59fae047ee969561a936d2d978
* presented citation count is obtained through Internet information analysis, and it is close to the number calculated by the Publish or PerishOpening in a new tab system.