Direct C-H methylation is a highly valuable approach for introducing methyl groups into organic molecules, particularly in pharmaceutical chemistry. Among the various methodologies available, photo-induced methylation stands out as an exceptional choice due to its mild reaction conditions, energy efficiency, and compatibility with functional groups. This article offers a comprehensive review of photochemical strategies employed for the direct and selective methylation of C(sp3)-H, C(sp2)-H, and C(sp)-H bonds in various organic molecules. The discussed methodologies encompass transition metal-based photocatalysis, organophotocatalysis, as well as other metal-free approaches, including electron donor-acceptor (EDA)-enabled transformations. Importantly, a wide range of easily accessible agents such as tert-butyl peroxide, methanol, DMSO, acetic acid, methyl halides, and even methane can serve as effective methylating reagents for modifying diverse targets. These advancements in photochemical C-H methylation are anticipated to drive further progress in the fields of organic synthesis, photocatalysis, and pharmaceutical development, opening up exciting avenues for creating novel organic molecules and discovering new drug compounds.
[ASAP] Microextraction–TQ–ICP–MS for the Direct Analysis of U and Pu from Cotton Swipes
Analytical Chemistry
DOI: 10.1021/acs.analchem.3c01022
The Mechanism of Lithium Zincate‐Mediated I/Zn Exchange Revisited: A Computational Micro‐Solvation Approach in THF
Lithium trialkylzincate-mediated I/Zn exchange reaction has been revisited computationally through a micro-solvation approach. A never yet investigated iodoaryl derivative bearing a potential bulky para-directing group, namely 4-iodobenzyl mesylate, was considered as a substrate. THF as typical solvent and Et3ZnLi have also been considered for the first time in such a reaction. Three mechanistic pathways have been calculated, including (1) a literature-inspired pathway with full preservation of the synergic character of the reagent as well as a complementary mesylate group-directed pathway, (2) a THF-solvated open complex-promoted pathway and (3) an anionic pathway. While the anionic pathway appeared to be unlikely, pathway involving a THF-solvated open zincate complex turned out to be the most energetically favoured. Equivalent thermodynamic profiles were found for both complementary pathways with preservation of the synergic character of the reagent, albeit a slight preference could be attributed to that occurring with initial chelation of Li to the mesylate group (OMs) through micro-solvation approach. The I/Zn exchange was shown to proceed through a lithium-assisted aryl shuttle-like process. The iodoaryl substrate is first converted into ArLi intermediate which in turns reacts with the remaining diorganozinc reagent.
Photoluminescence and radiation luminescence in a hybrid cuprous (I) halide: (4,4‐difluoro‐bipiperidinium)3Cu2I5
Copper (I) based halide scintillators have received high attention due to their high light yield. At the same time, researchers are increasingly interested in exploring organic-inorganic hybrid copper(I) based halides, due to the diversity and tunability of structures. Here, we describe high-efficiency photoluminescence and X-ray excited luminescence in (DFPD)3Cu2I5 (1) (DFPD = 4,4-difluoro-bipiperidinium). 1 is comprised of a unique [Cu2I5]3− cluster, which have typical structure allowing high-transition-probability self-trapped exciton emission (one Cu+ ion adopts the tetrahedral coordination geometry, the other trigonal planar coordination geometry, the Cu−Cu distance (2.574 Å) is short). Accordingly, 1 shows efficient yellow-green photoluminescence with the maximum at 527 nm, a full-width at half-maximum of 99.2 nm, a large Stokes shift of 214 nm (1.6 eV) and a quantum yield of 77.15%. Polycrystalline 1 can also convert high-energy X-ray photons into UV-visible pulsed fluorescence with the light yield of 5000 photons/MeV. This finding plays a valuable role in the development of organic-inorganic hybrid copper(I) based scintillators.
[ASAP] Dipodal Silanes Greatly Stabilize Glass Surface Functionalization for DNA Microarray Synthesis and High-Throughput Biological Assays
Analytical Chemistry
DOI: 10.1021/acs.analchem.3c03399
Efficient Oxidation of 5‐Hydroxymethylfurfural Using a Flavoprotein Oxidase from the Honeybee Apis mellifera
The chemical 5-hydroxymethylfurfural (HMF) can be derived from lignocellulose and is an interesting bio-based platform chemical as it has the potential to be transformed into numerous valuable building blocks such as the polymer-precursor 2,5-diformylfuran (DFF). To date, only few oxidases acting on HMF are known and by sampling atypical species, we discovered a novel flavin-dependent oxidoreductase from the honeybee Apis mellifera (beeHMFO). The enzyme can perform the chemoselective oxidation of HMF to DFF but can also readily accept other aromatic alcohols as substrates. The function of the enzyme may well be the antimicrobial generation of hydrogen peroxide using HMF, which is very abundant in honey. The discovery of this insect-derived flavoprotein oxidase holds promising potential in the synthesis of renewable products and demonstrates that insects can be an interesting source for novel biocatalysts.
Geometry and electronic properties of alkali metal (rubidium) doped boron clusters
The HOMO–LUMO molecular orbitals of RbB8 0/− clusters.
Abstract
Alkali metal-doped boron clusters have captured much attention because of their novel electronic properties and structural evolution. In the study of RbB n 0/− (n = 2–12) clusters, the minimum global search of the potential energy surface and structure optimization at the level of PBE1PBE by using the CALYPSO method and Gaussian package coupled with DFT calculation; the geometrical structures and electronic properties are systematically investigated. At n = 8, the ground-state structures are composed of an Rb atom above B atoms, forming a structurally stable pagoda cone. By stability analysis and charge transfer calculation, the RbB8 − cluster shows more stability. It found that s-p hybridization between Rb atom and B atoms as well as s-p hybridization between B atoms is one of the reasons for the outstanding stability exhibited in the RbB8 0/− clusters by using DOS and HOMO–LUMO orbital contour maps. The chemical bonding of the RbB8 0/− groups was analyzed by using the AdNDP method, and B atoms with larger numbers readily form multi-center chemical bonds with the Rb atom. From the results of the bonding analysis, the interaction between the Rb atom and B atoms strengthens the stability of the RbB8 0/− clusters. It is hoped that this work provides a direction for experimental manipulation.
Selective Self-Assembly of Gold Nanocrystals using Complementary Leucine Zipper Peptides
Chemistry Letters, Ahead of Print.
Dissolution and thermodynamic study of lamotrigine in propylene glycol + 1-propanol mixtures
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A review on ecology implications and pesticide degradation using nitrogen fixing bacteria under biotic and abiotic stress conditions
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