RESUMEN
Stoichiometric homeostasis is the ability of life to maintain inner chemical constancy despite changes in the environment and resources. Organisms can be stoichiometrically homeostatic to different degrees. This variation can be substantial even within species, but is ignored in most studies of ecological stoichiometry. Recent studies suggest that resource limitations are an important selective pressure behind homeostasis, but are contradictory in direction, likely owing to differences in nutrient storage strategies. Understanding the selective pressures underlying stoichiometric homeostasis, and its potential for rapid evolution, are key to predicting eco-evolutionary dynamics. This calls for the development of an evolutionary theory of stoichiometric homeostasis that incorporates rapid evolution, as well as for empirical studies to test the underlying mechanisms.
RESUMEN
Low-valent main group species have been evolving as powerful alternatives to transition metals over the years due to their advantages such as low toxicity and high abundance. However, the inability of main group elements to mimic the redox-switching property of transition metals often limits their role as catalysts. Here, we demonstrate the use of a low-valent phosphorus(I) compound as an efficient metal-free catalyst for the synthesis of biologically relevant γ-butyrolactones through dual activation under ambient reaction conditions. The highly nucleophilic phosphorus(I) center plays a key role in leading to this transformation. Extensive experimental and theoretical studies suggest that the phosphorus center exhibits facile switching between its reduced state [P(I)] and its oxidized state [P(III)] during this transformation, mimicking the behavior of transition metals.
RESUMEN
Herein, we report the first catalytic methylation of primary amides using CO2 as a C1 source. A bicyclic (alkyl)(amino)carbene (BICAAC) exhibits dual role by activating both primary amide and CO2 to carry out this catalytic transformation which enables the formation of a new C-N bond in the presence of pinacolborane. This protocol was applicable to a wide range of substrate scopes, including aromatic, heteroaromatic, and aliphatic amides. We successfully used this procedure in the diversification of drug and bioactive molecules. Moreover, this method was explored for isotope labelling using 13CO2 for a few biologically important molecules. A detailed study of the mechanism was carried out with the help of spectroscopic studies and DFT calculations.
RESUMEN
Bicyclic (alkyl)(amino)carbene (BICAAC) is introduced as a metal-free catalyst for the reduction of various nitriles to the corresponding amine hydrochloride salts in the presence of pinacolborane. Mechanistic investigations combining experiments and DFT calculations suggest a B-H addition to the carbene center, which acts as a carrier of the hydride source.
RESUMEN
A storable bicyclic (alkyl)(amino)carbene (BICAAC) stabilized two coordinate zinc(0) complex [(BICAAC)2Zn] (2) was synthesized. DFT calculations reveal that BICAAC plays a decisive role in imparting the stability to 2. This complex activates the C(sp3)-Cl bond of trityl chloride generating the Gomberg's free radical with greater efficiency than metallic Zn powder.