The utility of the intramolecular Nozaki-type coupling for the synthesis of macrocyclic benzo[b]thiophene-fused enediynes has been explored. The starting acyclic enediynes were prepared by the iodocyclization of 2-(buta-1,3-diynyl)thioanisoles followed by the Sonogashira cross-coupling of the resulting iodo-substituted benzo[b]thiophene with corresponding acetylenes. We found that Cr(II)-promoted intramolecular cyclization of 7-[2-(iodoethynyl)benzo[b]thiophen-3-yl]hept-6-ynal and 7-[3-(iodoethynyl)benzo-[b]thiophen-2-yl]hept-6-ynal resulted in the formation of 11-membered macrocyclic enediynes, while both expected 10-membered enediynes cannot be produced under the Nozaki-type reaction from corresponding 6-[3-(iodoethynyl)benzo[b]thiophen-2-yl]hex-5-ynal and 6-[2-(iodoethynyl)benzo[b]thiophen-3-yl]hex-5-ynal. In the case the reaction was catalyzed by Ni(II), the attack on a proximal triple bond led to the formation of 2-methylenecycloalkane-1-ol fragments, instead of macrocyclization. The DFT analysis of the ring strain in the benzo[b]thiophene-fused 10- and 11-membered enediyne-containing cycle provides the plausible explanation of the observed regioselectivity.

Original languageEnglish
Pages (from-to)151-167
Number of pages17
JournalArabian Journal of Chemistry
Volume12
Issue number2
Early online date18 May 2018
DOIs
StatePublished - Feb 2019

    Research areas

  • Allylic alcohols, Benzothiophene, Diacetylenes, Enediynes, Intramolecular Nozaki‐Hiyama‐Kishi reactions, Iodocyclization, ANTITUMOR ANTIBIOTICS, ELECTROPHILIC CYCLIZATION, DYNEMICIN-A, Intramolecular Nozaki-Hiyama-Kishi reactions, 10-MEMBERED RING, DEPENDENT BERGMAN CYCLIZATION, NUCLEOPHILIC ACTIVATION, DESIGNED ENEDIYNES, COUPLING REACTION, METHYL THIOGLYCOLATE, HIYAMA-KISHI REACTIONS

    Scopus subject areas

  • Chemical Engineering(all)
  • Chemistry(all)

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