An Investigation into the Stephens–Castro Synthesis of Dehydrotriaryl[12]annulenes: Factors Influencing the Cyclotrimerization.

Baxter, Paul N. W.; Al Ouahabi, Abdelaziz; Karmazin, Lydia; Varnek, Alexandre; Strub, Jean‐Marc; Cianferani, Sarah

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.

MONOMERS; ANNULENES; LIGANDS (Chemistry); WASTE products; CUPRATES

European Journal of Organic Chemistry, 2019, Vol 2019, Issue 40, p6783

1434-193X

Academic Journal

10.1002/ejoc.201901053