Dichotomous mechanistic behaviour in Narasaka-Heck cyclizations: electron rich Pd-catalysts generate iminyl radicals

Nicholas J Race, Adele Faulkner, Megan H Shaw, John Bower

Research output: Contribution to journalArticle (Academic Journal)peer-review

41 Citations (Scopus)
240 Downloads (Pure)

Abstract

Pd-catalyzed cyclizations of oxime esters with pendant alkenes are subject to an unusual ligand controlled mechanistic divergence. Pd-systems modified with electron deficient phosphines (e.g. P(3,5-(CF3)2C6H3)3) promote efficient aza-Heck cyclization, wherein C–N bond formation occurs via alkene imino-palladation. Conversely, electron rich ligands, such as P(t-Bu)3, cause deviation to a SET pathway and, in these cases, C–N bond formation occurs via cyclization of an iminyl radical. A series of mechanistic experiments differentiate the two pathways and the scope of the hybrid organometallic radical cyclization is outlined. This study represents a rare example in Pd-catalysis where selection between dichotomous mechanistic manifolds is facilitated solely by choice of phosphine ligand.
Original languageEnglish
Pages (from-to)1508-1513
Number of pages6
JournalChemical Science
Volume7
Issue number2
Early online date1 Dec 2015
DOIs
Publication statusPublished - 1 Feb 2016

Structured keywords

  • BCS and TECS CDTs

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