Radical Germylzincation of Aryl- and Alkyl-Substituted Internal Alkynes

Abstract

The stereoselective germylzincation of internal alkynes delivering trisubstituted vinylgermanes is achieved via a radical chain process involving Ph3GeH and Et2Zn with AIBN as initiator. Excellent levels of regiocontrol are observed for non-symmetric (aryl, alkyl)-substituted alkynes, as well as for propargylic alcohols with aryl-, alkyl-, or silyl-substituted alkynes. The germylzincation reaction can be combined in one pot with the Cu(I)-mediated electrophilic substitution of the C(sp 2 )-Zn bond to obtain synthetically challenging tetrasubstituted vinylgermanes.

Synthesis of 6-membered germacycles by intramolecular germylzincation of alkynes

“…The formation of a vinylzinc intermediate was proved by trapping with various conventional electrophiles. 9,11,12,18 The formation of a vinylzinc intermediate was first proved by quenching the reaction with D 2 O, and compound 3a-D was obtained in satisfactory 86% yields with full d -incorporation. We were then interested in the allylation of the substrates, in the presence of a copper catalyst (Table 3).…”

“…A key feature of this process is the formation of a C(sp 2 )–Zn bond that serves as handle for further functionalization in one-pot and thereby paves the way to modular strategies. 10 While alkyne silyl- and germylzincation reactions attract increasing interest, 11–13 this report represents the first example of intramolecular germylmetallation. 9…”

Advances in Transition‐Metal‐Catalyzed Hydrogermylation of Alkenes and Alkynes†

“…It involves the addition of the Ge—H bond to the unsaturated carbon‐carbon bonds, and generally needs to be facilitated by catalysts. The catalytic hydrogermylation reactions mainly include the following categories: free radical hydrogermylation initiated by photo‐ [ 32‐33 ] or thermal‐excitation, [ 34‐37 ] peroxides, [ 38‐40 ] organic boron reagents [ 41‐48 ] or others [ 49‐51 ] and transition‐metal‐catalyzed hydrogermylation. [ 9,52‐101 ] Transition‐metal‐catalyzed hydrogermylation has the potential advantages of selectivity control upon catalyst tuning.…”

Copper-Catalyzed Three-Component Germyl Peroxidation of Alkenes

“…To address these challenges and inspired by Perez-Luna’s reports on the germylzincation of alkynes in which the newly formed C­(sp 2 )–zinc bond allowed for further electrophilic elaborations (Scheme b), we envisioned that a sterically shielded and metal-stabilized tert -butyl peroxy radical might act as the persistent radical species to couple to the newly generated transient α-germyl alkyl radical, thus overcoming the competitive hydrogen atom transfer process to furnish the desired 1,2-germylfunctionalization product. Combined with our expertise in the radical-mediated peroxidation reaction, herein we describe the implementation of the copper-catalyzed radical germyl-peroxidation of alkenes to afford various highly functionalized germanium-containing molecules in good to excellent yields (Scheme c).…”