Mechanistic Dichotomy of Magnesium‐ and Zinc‐Based Germanium Nucleophiles in the C(sp³)−Ge Cross‐Coupling with Alkyl Electrophiles

Abstract

Robust procedures for two mechanistically distinct C(sp 3 )ÀGe bond formations from alkyle lectrophiles and germanium nucleophiles are reported. The germanium reagents were made available as bench-stable solutions by lithium-to-magnesium and lithium-to-zinc transmetalation, respectively.T he germanium Grignard reagent reacts with various primary and secondary alkyl electrophiles by an ionic nucleophilic displacement. Conversely,t he coupling of the corresponding zinc reagent requires an ickel catalyst, which then engages in radical bond formations with primary, secondary,a nd even tertiary alkylb romides.B oth methods avoid the regioselectivity issue of alkene hydrogermylation and enable the synthesis of aw ide range of functionalizeda lkylsubstituted germanes. Angewandte ChemieCommunications 6441

Pd/Ni-Catalyzed Germa-Suzuki coupling via dual Ge–F bond activation

“…1k In addition, Oestreich et al significantly advanced the use of Ge-based nucleophiles in Ge-C(sp 3 ) cross-coupling and described in 2019 a very elegant Germa-Negishi type reaction. 7 We envisioned a radically different approach, namely cross-coupling with a Ge-based electrophile. 8 Our recent discovery of facile Si-F bond activation thanks to transition metal / Lewis acid cooperation opened the way to catalytic Sila-Negishi coupling from fluoro-silanes.…”

Inorganometallics (Transition Metal–Metalloid Complexes) and Catalysis

“…Recently, Oestreich and co-workers have reported methods for the synthesis of C(sp 3 )−Ge bonds from alkyl electrophiles and germanium nucleophiles. 455 A germanium Grignard reagent was synthesized and shown to be active in reactions with primary and secondary alkyl bromides. The corresponding germanium zinc reagent (Ph 3 GeZnCl) undergoes a nickelcatalyzed reaction with primary, secondary, and, less successfully, tertiary alkyl bromides (Scheme 186).…”

Pd-Catalyzed Hydroxyl-Directed Cascade Hydroarylation/C–H Germylation of Nonterminal Alkenes and Aryl Iodides

“…Accordingly, considerable effort has been made to develop efficient and novel strategies for installing germyl moieties into organic molecules. Classical methodologies for the synthesis of arylgermanes have typically involved nucleophilic substitution of a Ge-electrophile by a Grignard reagent, or alternatively, direct coupling of Ar–H/X with a germyl reagent under transition-metal catalysis (Scheme a) . Furthermore, the use of directing groups to achieve palladium-catalyzed C­(sp 2 )–H germylation has been reported .…”