Synthesis of\nCyclic 2‑Aminodienes and Aminobenzofulvenes\nby Rhodium-Catalyzed Hydroaminative Cyclization of Diynes

Regioselective hydroaminative cyclizations of 1,5- and\n1,6-diynes\nvia double functionalization of an alkyne carbon were achieved using\na phosphine-quinolinolato (PNO) rhodium catalyst. While the reaction\nof 1,6-diynes with secondary amines provided cyclic 2-aminodienes,\nphenylene-tethered 1,5-diynes were transformed into benzofulvene derivatives.\nThe reaction is considered to proceed via in situ construction of\nan aminocarbene ligand, [2 + 2] addition with an internal alkyne moiety,\nand isomerization to an aminodiene structure. This hydroaminative\ncyclization proceeds just by heating the substrate with the rhodium\ncatalyst without adding any additive and provides a convenient route\nto access cyclic 2-aminodiene and aminobenzofulvene derivatives.