Photoredox Catalyzed Site-Selective Generation of Carbanions from C(sp3)-H bonds in Amines

The selective activation of sp3 carbon-hydrogen bonds in presence of multiple C¬-H bonds is challenging and remains of supreme importance in chemical research. Herein, we describe the activation of a C(sp3) H bond in α position to an amine via a carbanion intermediate. In the presence of several α amine sites, only one specific position is selectively activated. Applying this protocol, the proposed carbanion intermediate was effectively trapped with different electrophiles such as deuterium (D+), tritium (T+), or carbonyl compounds compiling over 50 examples. Further, this methodology was used to install deuterium or tritium in different drug derivatives (> 10 drugs) at a selected position in a late-stage functionalization. In addition, the protocol is suitable for a gram-scale synthesis and a detailed mechanistic investigation has been carried out to support our hypothesis.

Visible-Light Radical–Radical Coupling vs. Radical Addition: Disentangling a Mechanistic Knot

A highly enantioselective protocol has been recently described as allowing the synthesis of five-membered cyclic imines harnessing the selective generation of a β-Csp3-centered radical of acyl heterocyclic derivatives and its subsequent interaction with diverse NH-ketimines. The overall transformation represents a novel cascade process strategy crafted by individual well-known steps; however, the construction of the new C-C bond highlights a crucial knot from a mechanistically perspective. We believe that the full understanding of this enigmatic step may enrich the current literature and expand latent future ideas. Therefore, a detailed mechanistic study of the protocol has been conducted. Here, we provide theoretical insight into the mechanism using quantum chemistry calculations. Two possible pathways have been investigated: (a) imine reduction followed by radical–radical coupling and (b) radical addition followed by product reduction. In addition, investigations to unveil the origin behind the enantioselectivity of the 1-pyrroline derivatives have been conducted as well.

Demanding Power: Contentious Politics and Electricity in Pakistan

This paper explores Pakistan’s electricity supply crisis that lasted from 2007 to 2015, and the ensuing contention that shaped public discourse and political events in the country. During this period, which witnessed electricity outages of up to 14 hours per day, 456 incidents of contention took place, with just under 20 per cent escalating into some form of violence. Electricity became the number one political issue in the country and was integral in shaping the outcomes of the 2013 General Election. Following the election, public authorities undertook extensive investment to expand capacity and ensure consistency in supply while evading questions about affordability and sustainability. On the surface, this appears to be a case of extensive protest working towards shaping state responsiveness. And it is true that the state now sees supply as a non-negotiable aspect in the social contract with citizens. However, a range of factors contributed to the chronology and the selective, generation-focused nature of this response. On the other hand, citizen inclusion and participation in decision-making, and issues of affordability and sustainability, which impact vulnerable and disempowered groups the most, remain absent from the political and policy conversation around energy. This suggests that while protests were useful in generating a short-term response, their long-term legacy in empowerment related outcomes is less visible.

Unlocking the Accessibility of Alkyl Radicals from Boronic Acids through Hydrogen-bond Assisted Organophotoredox Activation

Despite their prevalence in organic synthesis, the application of boronic acids (BAs) as alkyl radical precursors in visible-light assisted photocatalyzed reactions has been limited by their high oxidation potential. This study demonstrates the remarkable ability of amide solvents viz. DMA (N,N-dimethylacetamide) to participate in hydrogen-bonding interactions with BAs, thus enabling the modulation of their oxidation potential towards the generation of alkyl radicals. The developed protocol is simple, robust and demonstrates broad applicability for alkylation, allylation and elimination reactions in batch and continuous flow. The application towards dehydroalanine allows the synthesis of unnatural amino acids. Furthermore, the chemo-selective generation of radical species from BAs, in the presence of boronic ester-containing molecules, is now feasible, endorsing plausible boron-selective (bio-) orthogonal modifications.

Unlocking the Accessibility of Alkyl Radicals from Boronic Acids through Hydrogen-bond Assisted Organophotoredox Activation

Despite their prevalence in organic synthesis, the application of boronic acids (BAs) as alkyl radical precursors in visible-light assisted photocatalyzed reactions has been limited by their high oxidation potential. This study demonstrates the remarkable ability of amide solvents viz. DMA (N,N-dimethylacetamide) to participate in hydrogen-bonding interactions with BAs, thus enabling the modulation of their oxidation potential towards the generation of alkyl radicals. The developed protocol is simple, robust and demonstrates broad applicability for alkylation, allylation and elimination reactions in batch and continuous flow. The application towards dehydroalanine allows the synthesis of unnatural amino acids. Furthermore, the chemo-selective generation of radical species from BAs, in the presence of boronic ester-containing molecules, is now feasible, endorsing plausible boron-selective (bio-) orthogonal modifications.

Non-Chromatographic Speciation of As by HG Technique—Analysis of Samples with Different Matrices

The applicability of the hydride generation (HG) sample introduction technique combined with different spectrochemical detection methods for non-chromatographic speciation of toxic As species, i.e., As(III), As(V), dimethylarsinate (DMA) and monomethylarsonate (MMA), in waters and other environmental, food and biological matrices is presented as a promising tool to speciate As by obviating chromatographic separation. Different non-chromatographic procedures along with speciation protocols reported in the literature over the past 20 year are summarized. Basic rules ensuring species selective generation of the corresponding hydrides are presented in detail. Common strategies and alternative approaches are highlighted. Aspects of proper sample preparation before analysis and the selection of adequate strategies for speciation purposes are emphasized.