Rhodium(I)-Catalyzed [2 + 2 + 2] Cycloaddition Reactions of Triacetylenic 15-Membered Aza Macrocycles: A Comparative Structural Study

A variety of new nitrogen-containing 15-membered triacetylenic macrocycles with one or two alkyl substituents in a propargylic position have been efficiently synthesized and completely characterized. These macrocyclic systems undergo [2 + 2 + 2] cycloaddition reactions, leading to the corresponding fused tetracycles with a benzene core on treatment with Wilkinson’s catalyst, [RhCl­(PPh3)3]. The effects of alkyl chains have been evaluated on both the efficiency of the reaction and the conformational and structural analysis of the reactants.