A DFT study on the mechanism of Rh-catalyzed competitive 1,2- versus 1,3-acyloxy migration followed by [5+1] and [4+1] cycloadditions of 1,4-enynes with CO

Dilek Coskun, Nurcan Tüzün*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

The mechanisms of the [RhCl(CO)2]2-catalyzed intramolecular cycloadditions of 3-acyloxy-1,4-enynes (ACEs) by CO with concominant acyloxy (OAc) migrations have been extensively investigated using density functional theory (DFT) calculations. All geometries were optimized at the B3LYP/6-31 + G(d) level (LANL2DZ for Rh). The effect of the nature of alkynes, terminal vs internal, has been rationalized by modelling possible intermediates and transition states for competitive 1,2- vs 1,3-migrations of acyloxy group and for further possible transformations with terminal and methyl substituted starting enynes. Experimental and mechanistic studies indicate that the formation reaction of the functionalized cyclopentenones involved a Saucy-Marbet 1,3-OAc migration of ACEs with terminal alkynes and subsequent [4 + 1] cycloaddition with CO, while the reaction for cyclohexadienones proceeded by a [5 + 1] type cycloaddition ACEs of substituted alkynes involving a Rautenstrauch 1,2-OAc migration by carbonylation. The acyloxy migration step is found to be the rate determining step from the DFT study and the predicted regioselectivity is in harmony with the experimental result. The calculations presented herein will contribute to understanding and controlling this effective Rh (I) catalyzed transformation reactions of 1,2 and 1,3-acyloxy migration followed by cycloaddition for further bicyclic cyclohexadienone and cyclopentenone derivatives in obtaining custom made products.

Original languageEnglish
Pages (from-to)97-103
Number of pages7
JournalJournal of Organometallic Chemistry
Volume851
DOIs
Publication statusPublished - 2017

Bibliographical note

Publisher Copyright:
© 2017

Funding

The authors gratefully acknowledge the ITU BAP Project (Grant No. 36543 ) and the National High Performance Computing Center at ITU (Grant No. 1002322012 ) for financial support and computational sources. D.C. thanks The Scientific and Technological Research Council of Turkey ( TUBITAK ) for a PhD scholarship.

FundersFunder number
ITU BAP36543
National High Performance Computing Center
TUBITAK
International Technological University1002322012
Türkiye Bilimsel ve Teknolojik Araştirma Kurumu

    Keywords

    • Acyloxy migration
    • Cycloaddition
    • DFT
    • Enynes
    • Rhodium
    • Transition metal

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