Three regioisomers - 1,4-bis(indazol-1-yl)butane, 1-(indazol-1-yl)-4-(indazol-2-yl)butane, and 1,4-bis(indazol-2-yl)butane - are prepared by the reaction of indazole double alkylation by 1,4-dibromobutane in a KOH/DMSO superbasic medium. The main reaction product - 1,4-bis(indazol-1-yl)butane (1,4-binb) - is isolated in individual form by recrystallization from isopropyl alcohol. The binuclear arene-ruthenium complex Ru2Cl4(1,4-binb)(p-cym)2 is prepared using the obtained 1,4-bis(indazol-1-yl)butane. The structure of the studied compounds is confirmed by SC-XRD. According to the obtained XRD data, indazole rings adopt an anti-conformation relative to the linker, and dihedral angles at the nitrogen atoms of indazole rings are 180° both in the structure of 1,4-bis(indazol-1-yl)butane and in that of the corresponding arene-ruthenium complex.
Pavlova et al. (2026) studied this question.