A Cu(I) Catalyzed Mild and General Synthesis of 1,4-Disubstituted-1,2,3-triazoles from Terminal Acetylenes and in situ Generated Alkyl Azides. -The reaction is catalyzed by cuprous cyanide, in situ generated from cupric sulfate and sodium cyanide. -(LOPEZ-RUIZ*, H.; ROJAS-LIMA, S.; DE LA CERDA-PEDRO, J. E.; AMADOR-SANCHEZ, Y. A.; CORTES-HERNANDEZ, M.; PEREZ-PEREZ, J.; Heterocycles 89 (2014) 1, 27-41, http://dx.doi.org/10.3987/COM-13-12764 ; Area Acad. Quim., Univ. Auton. Estado Hidalgo, 42184 Hidalgo, Mex.; Eng.) -H. Hoennerscheid 24-144
Crystalline 3-(4-aryl-1,2,3-triazol-1-yl)coumarins (ATCs) were prepared from commercial materials using a four-component methodology as a key step. In the present work, a feasible and environmentally friendly route to the title compounds was developed through the reaction between salicylaldehydes, ethyl bromoacetate, phenylacetylenes and sodium azide under mild conditions, with short reaction times and a simple workup. Crystalline solids are readily accessed from the featured products via solution processing and their arrays in the solid state were elucidated through SXRD; these molecules display a periodic overlap of π-systems, which facilitates carrier transport in organic electronic devices. Semiconductor band gaps for the obtained solids were derived through plane-wave DFT and compared with reference systems known to display superior performance in organic electronics. Thus ATCs represent attractive systems for research and implementation in molecular materials, a task which will be facilitated by the concise route herein described.
Cuprous oxide on charcoal (Cu 2 O/C), the preparation of which is described for the first time, catalyzes the formation of 1,4-disubstituted 1,2,3-triazoles from organic azides and terminal alkynes in good to excellent yields (69-94%). These disubstituted triazoles can be equally efficiently generated in a one-pot process from alkyl bromides, sodium azide, and terminal acetylenes in 50% aqueous isopropanol containing a suspension of the catalyst. This obviates the necessity to isolate potentially explosive organic azides.
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