Palladium-catalyzed highly chemo- and regioselective formal [2 + 2 + 2] sequential cycloaddition of alkynes: A renaissance of the well known trimerization reaction?

V. Gevorgyan, U. Radhakrishnan, A. Takeda, M. Rubina, M. Rubin, Y. Yamamoto

Research output: Contribution to journalArticle

109 Scopus citations

Abstract

A new concept of highly chemo- and regioselective formation of the benzene ring by a palladium-catalyzed formal [2 + 2 + 2] sequential intermolecular trimerization of, alkynes is proposed. Homodimerization of terminal alkynes and subsequent [4 + 2] benzannulation with diynes gives tetrasubstituted benzenes in moderate to good yields. The introduction of two different alkynes (terminal and internal) in the first step of the sequence allows for construction of pentasubstituted benzenes from three different acyclic acetylenic units. In all cases the tetra- and pentasubstituted benzenes are formed as a single reaction product without being accompanied by any of regio- or chemoisomers. A significant acceleration of the sequential trimerization reaction in the presence of Lewis acid/phosphine combined system was observed. Mechanistic studies reveal that the Lewis acid assisted isomerization of the E-enyne formed in the first step of the sequence to the more reactive Z-isomer is responsible for the observed acceleration effect. The proposed methodology provides a conceptually new and synthetically useful route to multifunctional aromatic compounds.

Original languageEnglish (US)
Pages (from-to)2835-2841
Number of pages7
JournalJournal of Organic Chemistry
Volume66
Issue number8
DOIs
StatePublished - Apr 20 2001
Externally publishedYes

ASJC Scopus subject areas

  • Organic Chemistry

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