Cucurbit[7]uril/CuCl promoting decomposition of 4-nitrobenzenediazonium in aqueous solution

4-Nitro-benzendiazonium (4-NBD) was found to form a 1:1 host-guest complex (NBD@CB) with cucurbit7]uril (CB7]) in aqueous solution and 4-NBD enters into the cavity of CB7] with a binding constant of 1.28 × 10⁵ L/mol. NBD@CB can be decomposed into a nitrobenzene/4-nitrophenol mixture in a high total yield (61% + 33%) in the presence of CuCl, unlike the decomposition of 4-NBD in the presence of either CB7] or CuCl, or both absence, where would result in significant amounts of unknown byproducts. This work might provide an economic and effective way to obtain arenes or phenols through the substitution of diazonium salts.