cis-Selective Hydrogenation of Aryl Germanes: A Direct Approach to Access Saturated Carbo- and Heterocyclic Germanes

Abstract

A catalytic approach of synthesizing the cis-selective saturated carbo-and heterocyclic germanium compounds (3D framework) is reported via the hydrogenation of readily accessible aromatic germanes (2D framework). Among the numerous catalysts tested, Nishimura's catalyst (Rh 2 O 3 /PtO 2 •H 2 O) exhibited the best hydrogenation reactivity with an isolated yield of up to 96%. A broad range of substrates including the synthesis of unprecedented saturated heterocyclic germanes was explored. This selective hydrogenation strategy could tolerate several functional groups such as −CF 3 , −OR, −F, −Bpin, and −SiR 3 groups. The synthesized products demonstrated the applications in coupling reactions including the newly developed strategy of aza-Giese-type addition reaction (C−N bond formation) from the saturated cyclic germane product. These versatile motifs can have a substantial value in organic synthesis and medicinal chemistry as they show orthogonal reactivity in coupling reactions while competing with other coupling partners such as boranes or silanes, acquiring a three-dimensional structure with high stability and robustness.

Recent Developments with Organogermanes: their Preparation and Application in Synthesis and Catalysis

“…Alternatively, based upon Wu's hydrosilylation conditions, [45] our group, amongst others, developed an organophotocatalytic hydrogermylation strategy of both linear and cyclic alkenes (Figure 13B, Method C ) [46] . However, given the robustness of the germane functionality, the C sp 3 −Ge bond can also be generated via hydrogenation of aryl germane substrates, which yielded cis ‐selective saturated, cyclic germane products [47] …”

Hydrogenation of functionalised pyridines with a rhodium oxide catalyst under mild conditions

“…We compared Rh 2 O 3 to the commercially available Nishimura's Catalyst, which is a combination of Rh 2 O 3 and PtO 2 and has been reported for the hydrogenation of aromatic compounds. [34][35][36][37] Interestingly, when using the same amount of rhodium, Rh 2 O 3 outperformed the Nishimura's Catalyst in activity (entries 17 and 18). 34 The conditions in entry 16 represent the now optimised reaction conditions for the substrate scope investigations, i.e.…”

Rhodium-catalyzed double hydroboration of pyridine: the origin of the chemo- and regioselectivities

“…(2) The resulting 3D framework often acts as a key structural motif of bioactive natural products and/or drugs. 11 (3) The sp 3 C–B bond installed via the double hydroboration of pyridines could be derivatized to various functional groups via simple organic reactions. 12…”