We next investigated the catalytic activity of various copper salts (Table 2). Cu(OAc)2 was found to be the most effective catalyst with a high yield of 96% (Table 2, entry 6). Interestingly, except for CuOAc/Cu(OAc)2, Cu(I) catalysts showed better catalytic activities than Cu(II) catalysts (Table 2, entries 1–12). Cu(OAc)2 was therefore adopted for the optimization of other reaction conditions. As to the temperature, 80 °C was found to be optimal. The reactions at lower temperatures generated less product (Table 2, entries 13 and 14). Lowering the catalyst load amount to 5 mol%, or reducing the reaction time to 12 h also resulted in decrease of yield (Table 2, entries 15 and 16).