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Breaking Conjugation: Unusual Regioselectivity with 2-Substituted Allylic Substrates in the Tsuji-Trost Reaction.


ABSTRACT: ?3-Allyl palladium complexes are key intermediates in Tsuji-Trost allylic substitution reactions. It is well known that (?3-1-aryl-3-alkyl substituted allyl)Pd intermediates result in nucleophilic attack at the alkyl substituted terminus. In contrast, the chemistry of (?3-1,2,3-trisubstituted allyl)Pd intermediates is relatively unexplored. Herein we probe the regioselectivity with 1,2,3-trisubstituted allylic substrates in Tsuji-Trost allylic substitution reactions. DFT investigation of cationic (?3-1-Ph-2-B(pin)-3-alkyl-allyl)Pd(PPh3)2 intermediates predict that nucleophilic attack should occur preferentially on anti-allyls rather than the syn-isomers to generate benzylic substitution products under Curtin-Hammett conditions. Experimentally, systematic studies with 1,2,3-trisubstituted allylic substrates revealed that a Linear Free Energy Relationship (LFER) is observed when Charton steric parameters of the C-2 substituents are plotted against the log of the ratio of regioisomers. Bulkier C-2 substituents in 1,2,3-trisubstituted ?3-allyl palladium intermediates provide stronger preference for nucleophilic attack at anti-oriented benzylic termini. Additionally, the geometry of 1,4-elimination products supports the presence of anti-allyl palladium intermediates.

SUBMITTER: Kim BS 

PROVIDER: S-EPMC4045119 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature

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Breaking Conjugation: Unusual Regioselectivity with 2-Substituted Allylic Substrates in the Tsuji-Trost Reaction.

Kim Byeong-Seon BS   Hussain Mahmud M MM   Norrby Per-Ola PO   Walsh Patrick J PJ  

Chemical science 20140301 3


η<sup>3</sup>-Allyl palladium complexes are key intermediates in Tsuji-Trost allylic substitution reactions. It is well known that (η<sup>3</sup>-1-aryl-3-alkyl substituted allyl)Pd intermediates result in nucleophilic attack at the alkyl substituted terminus. In contrast, the chemistry of (η<sup>3</sup>-1,2,3-trisubstituted allyl)Pd intermediates is relatively unexplored. Herein we probe the regioselectivity with 1,2,3-trisubstituted allylic substrates in Tsuji-Trost allylic substitution reacti  ...[more]

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