6-Endo-dig versus 5-exo-dig: Exploring Radical Cyclization Preference with First-, Second-, and Third-row Linkers using High-level Quantum Chemical Methods

Title
6-Endo-dig versus 5-exo-dig: Exploring Radical Cyclization Preference with First-, Second-, and Third-row Linkers using High-level Quantum Chemical Methods
Publication Date
2023-09-01
Author(s)
Baroudi, Abdulkader
Jaradat, Khaled
Karton, Amir
( author )
OrcID: https://orcid.org/0000-0002-7981-508X
Email: akarton@une.edu.au
UNE Id une-id:akarton
Type of document
Journal Article
Language
en
Entity Type
Publication
Publisher
Wiley-VCH Verlag GmbH & Co KGaA
Place of publication
Germany
DOI
10.1002/cphc.202300426
UNE publication id
une:1959.11/58475
Abstract

As an expansion upon Baldwin rules, the cyclization reactions of hex-5-yn-1-yl radical systems with different first-, second-, and third-row linkers are explored at the CCSD(T) level via means of the SMD(benzene)-G4(MP2) thermochemical protocol. Unlike C, O, and N linkers, systems with B, Si, P, S, Ge, As, and Se linkers are shown to favor 6-endo-dig cyclization. This offers fundamental insights into the rational synthetic design of cyclic compounds. A thorough analysis of stereoelectronic effects, cyclization barriers, and intrinsic barriers illustrates that structural changes alter the cyclization preference by mainly impacting 5-exo-dig reaction barriers. Based on the high-level computational modeling, we proceed to develop a new tool for cyclization preference prediction from the correlation between cyclization barriers and radical structural parameters (e. g., linker bond length and bond angle). A strong correlation is found between the radical attack trajectory angle and the reaction barrier heights, i. e., cyclization preference. Finally, the influence of stereoelectronic effects on the two radical cyclization pathways is further investigated in stereoisomers of hypervalent silicon system, which provides novel insight into cyclization control.

Link
Citation
ChemPhysChem, 24(17), p. 1-11
ISSN
1439-7641
1439-4235
Start page
1
End page
11

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