Chiral Binaphthalenes Bearing Two Pyridine Ligands Attached Via Acetylene Spacers. Synthesis and Coordination Study

Dedicated to Professor Štefan Toma on the occasion of his 70th birthday. An effective methodology has been developed for the synthesis of enantiopure 2,2′-dialkynylated 1,1′-binaphthalene derivatives. Enantiopure 2,2′-diiodo-1,1′-binaphthalene (10) provided 2,2′-diethynyl-1,1′-binaphthalene (16) in the Negishi alkynylation supported by microwave irradiation in a very good yield with conservation of stereochemical informa-tion. The Stephen–Castro alkynylation of 10 afforded products in lower yields; however, in stereoconservative manner as well. Terminal diacetylene 16 served as precursor in the Sonogashira cross-coupling reaction to give new bispyridine derivatives 7–9 as potential lig-ands in moderate to high yields. Coordination of bispyridines with Zn2+ and Ag+ ions was observed by NMR and CD spectroscopy. The coordination ability of bis(2-pyridylethynyl) derivative 7 to palladium cation was determined by X-ray structure analysis