Copper (II) as catalyst for intramolecular cyclization and oxidation of (1,4-phenylene)bisguanidines to benzodiimidazole-diylidenes

Publication date: February 2020Source: Journal of Catalysis, Volume 382Author(s): Angela Mesias-Salazar, Oleksandra S. Trofymchuk, Constantin G. Daniliuc, Antonio Antiñolo, Fernando Carrillo-Hermosilla, Fabiane M. Nachtigall, Leonardo S. Santos, René S. RojasAbstractA synthetically useful approach of catalytic intramolecular cyclization and oxidation of 2′,2′-(1,4-phenylene)bis(1,3-dialkyl)guanidines (Alkyl = isopropyl 1 or cyclohexyl 2) catalyzed by copper acetate in acetonitrile under air was studied by on line monitoring of the reaction by ESI-MS. All-important intermediates organic species were intercepted during the experiment confirming for the first time the stepwise (1,4-phenylene)bisguanidines cyclization and oxidation mechanism. Moreover, performed collision-induced dissociation (CID) experiments were also applied as a structure elucidation tool. Bimetallic copper intermediates Cu1 ([C28H48Cu2N6O10 + H]+) of m/z 755 and Cu2 [C22H36Cu2N6O4 + H]+ of m/z 575 were documented. The plausible key mechanistic steps involving the formation of organic and inorganic intermediates detected by in situ monitoring of the reaction are presented.Graphical abstract

Source: Journal of Catalysis - January 3, 2020 Category: Chemistry Source Type: research