“…Although homogeneous catalysts involving 42 the use of Ru [21][22][23], Rh [24,25], Ir [26], and Pd complexes [27,28] 43 are often reported in the literature, they are commonly limited to 44 asymmetric hydrogentation of N-protected or substituted indoles. 45 Compared with homogeneous catalysts, heterogeneous catalysts 46 are relatively stable in air and water and easy to store and recycle 47 [29][30][31]. Currently, there are only a few reports on heterogeneous 48 hydrogenation of indole to indoline.…”