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An Investigation into the Stephens–Castro Synthesis of Dehydrotriaryl[12]annulenes: Factors Influencing the Cyclotrimerization
Author(s) -
Baxter Paul N. W.,
Al Ouahabi Abdelaziz,
Karmazin Lydia,
Varnek Alexandre,
Strub JeanMarc,
Cianferani Sarah
Publication year - 2019
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201901053
Subject(s) - annulene , dimer , monomer , phosphine , chemistry , dilution , stereochemistry , crystallography , organic chemistry , polymer , physics , catalysis , thermodynamics
Detailed investigation into the CuX/base/phosphine modified Stephens–Castro syntheses of dehydrotriaryl[12]annulenes 1 – 3 have shown that cyclization is suppressed by excess CuX, strong donor ligands, high dilution conditions, and thermally unstable ethynylcuprate monomers. Surprisingly, intermediate dimer 16 plays only a minor role in the formation of 2 and 4 . Overall, our findings are consistent with a cyclization pathway governed more by the nature of prior self‐association of the ethynylcuprate monomers. Crystallographic characterization of tetrameric by‐product 4 , is also reported and revealed that it assembles into tubular stacks in the solid state.