The focus of this review is to provide an overview of the field of organocatalysed photoredox chemistry relevant to synthetic medicinal chemistry. Photoredox transformations have been shown to enable key transformations that are important to the pharmaceutical industry. This type of chemistry has also demonstrated a high degree of sustainability, especially when organic dyes can be employed in place of often toxic and environmentally damaging transition metals. The sections are arranged according to the general class of the presented reactions and the value of these methods to medicinal chemistry is considered. An overview of the general characteristics of the photocatalysts as well as some electrochemical data is presented. In addition, the general reaction mechanisms for organocatalysed photoredox transformations are discussed and some individual mechanistic considerations are highlighted in the text when appropriate.
Carbon dioxide (CO2) impacts
every aspect of life, and
numerous sensing technologies have been established to detect and
monitor this ubiquitous molecule. However, its selective sensing at
the molecular level remains an unmet challenge, despite the tremendous
potential of such an approach for understanding this molecule’s
role in complex environments. In this work, we introduce a unique
class of selective fluorescent carbon dioxide molecular sensors (CarboSen)
that addresses these existing challenges through an activity-based
approach. Besides the design, synthesis, and evaluation of these small
molecules as CO2 sensors, we demonstrate their utility
by tailoring their reactivity and optical properties, allowing their
use in a broad spectrum of
multidisciplinary applications, including atmospheric sensing, chemical
reaction monitoring, enzymology, and live-cell imaging. Collectively,
these results showcase the potential of CarboSen sensors as broadly
applicable tools to monitor and visualize carbon dioxide across multiple
disciplines.
Many methods report the scission of N−O bonds of aromatic heterocycles and their subsequent functionalization. Oxidative addition is one of the presumed pathways through which aromatic N−O bond activation with transition metals is achieved. We report the first well-defined pathway of (benz)isoxazole's aromatic N−O bond activation through oxidative addition. We also provide control experiments, which show that aromatic N−O bonds may be broken by strong inorganic reductants. These results highlight that N−O bonds are susceptible to both reduction and oxidative addition, which has important implications for catalysis. Exploring the reactivity of one of these complexes toward a series of electrophiles leads to the discovery of a Staudingertype β-lactam synthesis upon the reaction with a ketene. Finally, we demonstrate that the choice of different metal/ligand combinations allows for selective oxidative addition into either C−I bonds or N−O bonds in the presence of the other.
Alkylpalladium complexes are important intermediates in several industrially relevant catalytic reactions such as the Mizoroki–Heck, alkyl C–H activation and ethylene polymerisation. Beta-elimination - of either a hydride (β-Η) or a heteroatom (β-Χ) - is the most common decomposition pathway for these intermediates; this can either promote the desired reaction as in the Mizoroki–Heck reaction, or it can hinder reaction progress as in ethylene/vinyl halide co-polymerisations. Despite the importance of these elimination 15 processes, little mechanistic understanding exists with respect to the factors that control them. We present a systematic investigation of the factors governing the competition between β-Η and β-Χ in catalytically relevant alkylpalladium complexes. These results enabled us to derive selection rules which dictate ligand choice to control selectivity for either elimination. This knowledge may allow chemists to manipulate beta-eliminations in the design of chemoselective catalytic reactions for a wide range of applications.
Many methods report the scission of the N–O bonds of aromatic heterocycles and their subsequent functionalization. Oxidative addition is one of the presumed pathways through which aromatic N–O bond activation with transition metals is achieved. We report the first well-defined pathway of (benz)isoxazole’s aromatic N–O bond activation through oxidative addition. We also provide control experiments which show that aromatic N–O bonds may be broken by strong inorganic reductants. These results highlight that N–O bonds are susceptible to both reduction and oxidative addition, which has important implications for catalysis. Exploring the reactivity of one of these complexes towards a series or electrophiles led to the discovery of a Staudingertype β-lactam synthesis upon reaction with a ketene. Finally, we demonstrate that choice of different metal/ligand combinations allows for selective oxidative addition into either C–I bonds or N–O bonds in the presence of the other.
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