Theoretical Study of NCO and RCCH (R = H, CH3, F, Cl, CN) [3 + 2] Cycloaddition Reactions

Hsin Tsung Chen, Jia Jen Ho

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Abstract

We carried out a theoretical study of the radical [3 + 2] cycloaddition reaction of NCO + RCCH (R = H, CH3, F, Cl, CN), which produced a five-membered ring heterocyclic oxazole. An asynchronous two-bond formation mechanism was found, which led to a certain regioselectivity in the products when the substituted alkyne was used as a reactant. The preferable reactive sites of RCCH in various substituents are calculated by employing the Fukui functions and HSAB theory, and the results are in good agreement (except R = F) with the calculated energy barriers of the transition states in the potential energy surfaces. The N atom of NCO attacks the unsubstituted carbon atom of RCCH first, followed by the ring closure of the O atom with the other carbon atom to form the substituted oxazole. The order of the calculated first transition barriers (uts1) in the substituted alkynes (RCCH) is R = H > F > CN > Cl > CH3 and that for the second transition barriers (uts2), R = H > CH3 > CN > Cl > F. The reason for the decreased transition barriers of the substituted alkynes is analyzed.

Original languageEnglish
Pages (from-to)7643-7649
Number of pages7
JournalJournal of Physical Chemistry A
Volume107
Issue number38
DOIs
Publication statusPublished - 2003 Sep 25

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Alkynes
Cycloaddition
Cycloaddition Reaction
cycloaddition
Oxazoles
alkynes
Theoretical Models
oxazole
Atoms
Carbon
atoms
Regioselectivity
Potential energy surfaces
carbon
rings
Energy barriers
Catalytic Domain
attack
closures
potential energy

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Theoretical Study of NCO and RCCH (R = H, CH3, F, Cl, CN) [3 + 2] Cycloaddition Reactions. / Chen, Hsin Tsung; Ho, Jia Jen.

In: Journal of Physical Chemistry A, Vol. 107, No. 38, 25.09.2003, p. 7643-7649.

Research output: Contribution to journalArticle

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AB - We carried out a theoretical study of the radical [3 + 2] cycloaddition reaction of NCO + RCCH (R = H, CH3, F, Cl, CN), which produced a five-membered ring heterocyclic oxazole. An asynchronous two-bond formation mechanism was found, which led to a certain regioselectivity in the products when the substituted alkyne was used as a reactant. The preferable reactive sites of RCCH in various substituents are calculated by employing the Fukui functions and HSAB theory, and the results are in good agreement (except R = F) with the calculated energy barriers of the transition states in the potential energy surfaces. The N atom of NCO attacks the unsubstituted carbon atom of RCCH first, followed by the ring closure of the O atom with the other carbon atom to form the substituted oxazole. The order of the calculated first transition barriers (uts1) in the substituted alkynes (RCCH) is R = H > F > CN > Cl > CH3 and that for the second transition barriers (uts2), R = H > CH3 > CN > Cl > F. The reason for the decreased transition barriers of the substituted alkynes is analyzed.

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