Cobalt-Catalyzed (E)-β-Selective Hydrogermylation of Terminal Alkynes

Abstract

A cobalt-catalyzed method for the hydrogermylation of alkynes is reported, providing a selective and accessible route to (E)-β-vinyl(trialkyl)germanes from terminal alkynes and HGeBu 3 . As shown in multiple examples, the developed method demonstrates a broad functional group tolerance an practical utility for late-stage hydrogermylation of natural products. The method is compatible with alkynes bearing both aryl and alkyl substituents, providing unrivaled selectivity for previously challenging 1°alkyl-substituted alkynes. Moreover, the catalyst used in this method, Co 2 (CO) 8 , is a cheap and commercially available reagent. Conducted mechanistic studies supported the syn-addition of Bu 3 GeH to an alkyne π-complex.

Regioselective Access to α-Vinylsilanes and α-Vinylgermanes by Cobalt-Catalyzed Migratory Hydrofunctionalization of 2-Alkynes

“…After successful accomplishment of the cobalt-catalyzed migratory hydrosilylation of 2-alkynes, we sought to expand the scope of this type of alkyne hydrofunctionalization by using hydrogermane as a hydroelement source. While the synthetic utilities of organogermanes have been previously underestimated, several researchers have recently unveiled the unique synthetic applicability of the organogermanes toward chemical synthesis, and there is an ongoing effort to explore new routes for selective access to the organogermane moieties. , In addition, since hydrogermanes are known to serve as electrophiles that can operate through either one-electron or two-electron processes, it could be promising in our mechanistic platform if we could find a proper way to handle the hydrogermane source. To date, there are only two examples that describe selective catalytic hydrogermanylation for α-vinylgermanes, including Rh­(I) catalysis that describes a single example of the catalytic transformation of phenylacetylene into α-vinylgermane in the presence of a large excess of hydrogermane and Au/TiO 2 -catalyzed hydrogermanylation of terminal allenes .…”

“…α-Vinylsilanes have been utilized as versatile building blocks for applications in organic synthesis, materials science, and bioconjugation due to their stability, nontoxicity, and ease of handling, whereas α-vinylgermanes have recently emerged as promising coupling partners or precursors for organic transformations . In this context, several elegant methodologies have been devised to prepare α-vinylsilanes such as substitution reactions using propargylic chloride, regioselective allene hydrosilylations, migratory semihydrogenation of alkynylsilanes, and silylcupration or Markovnikov hydrosilylation of terminal alkynes .…”

Cu-Catalyzed Enantioselective Hydrogermylation: Asymmetric Synthesis of Unnatural β-Germyl α-Amino Acids

“…Furthermore, changing the metal catalyst into Cu­(OAc) still gave no reactivity in the hydrosilylation reaction between 2a and dihydrosilane 1a (Table , entry 5), while to our delight, the desired β-germyl α-amino acid product 3ba was obtained in 95% yield with 35% ee in the hydrogermylation reaction between 2a and dihydrogermane 1b (Table , entry 6). It is worth mentioning that, despite a number of hydrogermylation reactions having been reported, − to our knowledge, here we realized the first example of catalytic enantioselective hydrogermylation of alkenes.…”

Copper-Catalyzed Germyl-Azidation of Alkenes with Germanium Hydrides and Trimethylsilyl Azide

“…Nevertheless, in comparison to the well-established carbon and silyl chemistry, the development of catalytic methods for the synthesis of analogous organogermanes has lagged behind. In this context, hydrogermylation of alkenes with R 3 GeH has been demonstrated as a powerful tool to synthesize germanium-containing molecules . Alternatively, selective 1,2-germyl-functionalization of alkenes that assembles a germyl group and another functional group (except for the hydrogen atom) across the CC double bond in one step could provide an efficient and convenient access to construct complex functionalized organogermanium compounds .…”