Ynamides are fascinating small molecules with complementary reactivities under radical, ionic, and metal-catalyzed conditions. We report herein synthetic and DFT investigations of palladium-catalyzed ligand-controlled regiodivergent hydrometalation reactions of ynamides. Germylated and stannylated enamides are obtained with excellent α,E- or β,E-selectivities and a broad functional group tolerance. Such a regiodivergent palladium-catalyzed process is unique in ynamide chemistry and allows for the elaboration of metalated enamides that are useful building blocks for cross-coupling reactions or heterocyclic chemistry. DFT calculations fully support the experimental data and demonstrate the crucial roles of the trans-geometry of the [H-Pd(L)-Ge] complex, as well as of the steric requirements of the phosphine ligand. In addition, these calculations support the prevalence of a hydro-palladation pathway over a metal palladation of the π system of the ynamide.

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Ligand-Controlled Regiodivergent Palladium-Catalyzed Hydrogermylation of Ynamides.

A simple access to silylated and germylated binuclear heterocycles, based on an original anionic rearrangement, is described. A set of electron-rich and electron-poor silylated aromatic and heteroaromatic substrates were tested to understand the mechanism and the factors controlling this rearrangement, in particular its regioselectivity. This parameter was shown to follow the rules proposed before from a few examples. Then, the effect of the substituents borne by the silicon itself, in particular the selectivity of the ligand transfer, was studied. Additionally, this chemistry was extended to germylated substrates. A hypervalent germanium species, comparable to the putative intermediate proposed with silicon, seems to be involved. However, a pathway implicating the elimination of LiCH2Cl was observed for the first time with this element, leading to unexpected products of the benzo-oxa (or benzo-aza) germol-type.

Anionic Access to Silylated and Germylated Binuclear Heterocycles

Syntheses, Structures, and Sensory Characteristics of the Perfume Ingredient Majantol and Its Analogs Sila-majantol and Germa-majantol: A Study on C/Si/Ge Bioisosterism

1
Introduction

2
Toxicity

3
Neurotropic Activity

4
Cardiovascular Activity

5
Antitumor, Antiviral and Immunomodulating Activity

6
Radioprotective Activity

7
Miscellaneous Activities



Keywords:

biological activity of organogermanium compounds;
neurotropic activity;
Germanium - middle element of Periodic Group IVA.;
acute toxicity of thienylgermatranes;
neurotropic activity of germatranes;
furan-containing germyl-substituted amines;
2-carboxyethylgermanium sesquioxane and cardiovascular activity;
antitumor, antiviral and immunomodulating activity

Biological Activity of Organogermanium Compounds

New bicyclic sila-heterocycles: syntheses and crystal structure analyses of rac-7-ethoxy-2,2-diorganyl-2,3,5,7a-tetrahydro-1H-3a,6-diaza-2-sila-inden-4-ones

In context with systematic investigations on C/Si/Ge bioisosterism, the following studies were carried out: (a) synthesis and pharmacological characterization of centrochiral enantiomerically pure germanium-based muscarinic antagonists; (b) synthesis and pharmacological characterization of a germanium-containing decapeptide; (c) studies on the metabolism of a germanium-based drug in the rat; (d) synthesis of centrochiral enantiomerically pure germanes using biotransformations with whole microorganisms or isolated enzymes. These investigations demonstrated that there are distinct bioisosteric relationships between the C/Si/Ge analogues studied.

T. Beckerss

Papers

Bioorganogermanium Chemistry: Studies on C/Si/Ge Bioisosterism