2가 구리 이온을 함유한 화합물로 CuBr2를 촉매로 사용하였으나 반응이 전혀 진행되지 않았고, 크기가 약 3 µm인 dendritic Cu 분말은 촉매로서 좋은 활성을 나타내었다.
As a compound containing divalent copper ions, CuBr2 was used as a catalyst, but the reaction failed to proceed at all, and dendritic Cu powder by having a size of about 3 µm revealed good activity being a catalyst.