Green Synthesis of 1,1'-Carbonyldiimidazole Using Copper Oxide Nanofiber as a Heterogeneous Catalyst.

Poly(vinyl pyrrolidone) (PVP)/copper oxide composite nanofibers were prepared by electrospinning technique using PVP and copper acetate as precursors and calcinated at high temperature to yield polymer free, phase pure copper oxide nanofibers (CuO NFs). The powder X-ray diffraction (XRD) pattern, transmission electron microscopic (TEM) images and selected area electron diffraction pattern (SAED) results showed that the calcinated CuO NFs were crystalline with 166 nm diameter and monoclinic in phase. From the catalytic application point of view, the newly prepared electrospun CuO NFs were tested for N-arylation of imidazole using aryl halides. To our surprise, 1,1'-carbonyldiimidazole (CDI) was obtained under the conditions of air and nitrogen atmosphere. Furthermore, the same product CDI was obtained from the reactions where in no aryl halide was involved but with imidazole alone as substrate. Our methodology to prepare CDI is free from the use of toxic phosgene as carbonyl source, as reported earlier. Hence, the present process possesses some advantages such as green and cost effective alternate for the existing synthesis method.