Readily available o′-alkenyl-o-alkynylbiaryls, a particular type of 1,7-enynes, undergo a selective cycloisomerization reaction in the presence of a gold­(I) catalyst to give interesting phenanthrene and dihydrophenanthrene derivatives in high yields. The solvent used provokes a switch in the evolution of the gold intermediate and plays a key role in the reaction outcome.

Metal-free borylative cyclization of biphenylembedded 1,3,5-trien-7-ynes in the presence of simple and inexpensive BCl 3 provided synthetically useful borylated building blocks. The outcome of the process depends on the reaction temperature, with borylated phenanthrenes obtained at 60 °C and phenanthrenefused borylated cyclobutanes formed at 0 °C. Based on DFT calculations, a mechanism for these novel transformations has been proposed, which involves an uncommon skeletal rearrangement, including migration of a methyl group and alkyne fragmentation, unprecedented in BCl 3 -promoted cyclization reactions.

Gold(I)‐catalyzed cyclization of o‐alkenyl‐o’‐alkynylbiaryls in the presence of external or internal nucleophiles provides a straightforward access to phenanthrene‐based polycycles, which are of considerable interest in materials science. Thus, their reactions with alcohols yield functionalized dihydrophenanthrenes, in a process that can also be carried out intramolecularly, to provide phenanthrene‐derived heteropolycyclic compounds. Moreover, benzo[b]triphenylenes can be synthesized from o‐methoxyvinyl‐o’‐alkynylbiaryls, in a reaction in which an (hetero)aryl substituent at the triple bond acts as an internal nucleophile.

Die Titelverbindung (I) wird einerseits durch direkte Alkylierung in die Dialkylderivate (II) übergeführt, wobei das Isomere (III) als Nebenprodukt entsteht.

Metal-free borylative cyclization of biphenylembedded 1,3,5-trien-7-ynes in the presence of simple and inexpensive BCl 3 provided synthetically useful borylated building blocks. The outcome of the process depends on the reaction temperature, with borylated phenanthrenes obtained at 60 °C and phenanthrenefused borylated cyclobutanes formed at 0 °C. Based on DFT calculations, a mechanism for these novel transformations has been proposed, which involves an uncommon skeletal rearrangement, including migration of a methyl group and alkyne fragmentation, unprecedented in BCl 3 -promoted cyclization reactions.