The reaction of 1-hydroxypyridine-2-thione with Os3(CO)11(NCMe) has yielded three new complexes Os3(CO)10(μ-H)(μ-η1-S-C5H4N(O)) (1, 11% yield), Os3(CO)10(μ-H)(η2-S-C5H4N(O)) (2, 16% yield), and Os3(CO)9(μ-H)(μ-η2:η1-SC5H4N(O)) (3, 3% yield). Similarly, treatment of complex Os3(CO)10(NCMe)2 with this ligand has produced the major complexes 1 and trace of 3. Prolonging the above two reactions increased the yield of 3. Treatment of 1-hydroxypyridine-2-thione with triosmium isocyanide complexes Os3(CO)10(CNR)(NCMe) (a, R = CH2Ph; b, R = Pr) has led to the formation of Os3(CO)9(μ-H)(CNR)(η2-SC5H4N(O)) (4), Os3(CO)10(μ-η1-CNHCH2Ph)(μ-η1-S-C5H4N(O)) (5), and Os3(CO)9(μ-H)(CNR)(μ-η1-S-C5H4N(O)) (6). The 4:5 ratio depended upon the nature of the alkyl groups of the coordinated isocyanide. Reaction of either 1 or 2 with Me3NO resulted in CO loss and formation of complex 3. Thermolysis of 1 at 80 °C generated Os3(CO)9(μ-H)(μ3-pyS) (7), Os3(CO)9(μ-OH)(μ3-pyS) (8), and byproduct CO2. Upon being heated at 80 °C, 3 was converted to 7 and 8 in a ratio of 1:4 as indicated by an in-situ NMR study. These observations show that 3 is an intermediate for the formation of 8 from 1. Crystal structures of 1, 4b, 5a, and 8 were determined by X-ray diffraction analyses. The overall results indicate that the N-oxide group in these complexes exhibits versatile bonding modes on triosmium clusters.

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We report on a copper-catalyzed three-component reaction for the synthesis of disubstituted nicotinonitriles using 3bromopropenals, benzoylacetonitriles, and ammonium acetate (NH 4 OAc). The Knoevenagel-type condensation of 3bromopropenals with benzoylacetonitriles gives δ-bromo-2,4-dienones that contain strategically placed functional groups that react with the ammonia generated in situ to give the corresponding azatrienes. These azatrienes can then be transformed into trisubstituted pyridines under the reaction conditions via a reaction sequence involving 6π-azaelectrocyclization and aromatization.