Unusual Regioselectivity in Palladium-Catalyzed Cyclization of 6-(Pronucleophile-tethered)-3-bromo-1,3-hexadienes: Experimental Observations and Theoretical Rationales
Issued Date
2026-05-01
Resource Type
ISSN
02767333
eISSN
15206041
Scopus ID
2-s2.0-105040009781
Journal Title
Organometallics
Volume
45
Issue
10
Start Page
1132
End Page
1143
Rights Holder(s)
SCOPUS
Bibliographic Citation
Organometallics Vol.45 No.10 (2026) , 1132-1143
Suggested Citation
Kititheerakul T., Horie M., Kirihata N., Ichio H., Ogasawara M., Surawatanawong P. Unusual Regioselectivity in Palladium-Catalyzed Cyclization of 6-(Pronucleophile-tethered)-3-bromo-1,3-hexadienes: Experimental Observations and Theoretical Rationales. Organometallics Vol.45 No.10 (2026) , 1132-1143. 1143. doi:10.1021/acs.organomet.6c00028 Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/117054
Title
Unusual Regioselectivity in Palladium-Catalyzed Cyclization of 6-(Pronucleophile-tethered)-3-bromo-1,3-hexadienes: Experimental Observations and Theoretical Rationales
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Abstract
A palladium-catalyzed reaction of a series of 6-(pronucleophile-tethered)-3-bromo-1,3-hexadiene substrates 1, in which a bromodiene unit and a pronucleophile moiety are connected with a –(CH<inf>2</inf>)<inf>2</inf>– linker, was investigated. Under optimized conditions, intramolecular nucleophilic substitution and cyclization predominantly took place to give the corresponding vinylcyclopentene derivatives 2 in good to excellent yields. The reaction proceeded through the alkylidene-π-allylpalladium intermediate M<inf>2</inf>, and the tethered soft nucleophile moiety attacked at the internal sp<sup>2</sup>-carbon in the alkylidene-π-allylpalladium moiety. This is an unprecedented “reverse” regioselectivity in the palladium-catalyzed substitution of 2-bromo-1,3-dienes with a soft nucleophile. According to our density functional theory calculations, alkylidene-π-allylpalladium generally favors nucleophilic attack at the terminal sp<sup>3</sup>-C1 carbon due to the weaker Pd–C1 bond and a favorable obtuse attack angle. However, bearing a short –(CH<inf>2</inf>)<inf>2</inf>– tether, M<inf>2</inf> necessarily imposes an acute attack angle at the terminal sp<sup>3</sup>-C1, and this also leads to an unfavorable ring strain in the seven-membered endocyclic allene product. As a result, the intramolecular nucleophilic attack at the internal sp<sup>2</sup>-C3 becomes predominant, accounting for the observed “reverse” regioselectivity.