Synlett

A green and sustainable electrochemical approach is developed for the regioselective C3–H trifluoro/difluoromethylation of 2H-indazoles at room temperature. Relatively less expensive C-soft (+)/Ni-foam (–) electrodes are utilized to selectively functionalize the 2H-indazoles effectively by avoiding the use of any external oxidant and transition-metal salt. Moreover, along with the C3–H trifluoromethylation, for the very first time, direct C3–H difluoromethylation of 2-phenyl-2H-indazoles is accomplished. Diverse C3–H trifluoro/difluoromethylated 2H-indazoles having an array of functionalities are successfully synthesized in moderate to very good yields. As an application, a precursor of both an estrogen receptor ligand and an acetyl Co-A carboxylase inhibitor is synthesized. A plausible reaction mechanism is proposed based on control experiments and cyclic voltammetry studies.

Epoxidation of α,β-unsaturated ketones under visible-light irradiation constitutes a significant chemical transformation with potential applications in the synthesis of epoxypropane derivatives. An organophotoredox catalytic system is herein reported to facilitate efficient aerobic epoxidation. This protocol enables the conversion of α,β-unsaturated ketones into their corresponding epoxy products with moderate to high yields under benign reaction conditions. The methodology demonstrates broad functional-group compatibility, providing a reliable and direct route to a variety of functionalized epoxypropane compounds. Additionally, the absence of heavy metals in this strategy renders it particularly suitable for the pharmaceutical industry, offering a new avenue for the synthesis of epichlorohydrin drugs.

A simple strategy for the synthesis of a variety of tetrahydropyridines in good to excellent yields via a Cu(OTf)2 catalyzed quaternary ammonium salt mediated ring-opening of activated azetidines followed by cyclization with alkynes in a domino ring-opening cyclization (DROC) is described. The formation of the products has been explained by an SN2-type ring-opening of azetidines with alkynes.

Synlett 2024; 35: A165-A181DOI: 10.1055/s-0043-1764000Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

Synlett 2024; 35: V-DOI: 10.1055/s-0043-1773497Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

SynlettDOI: 10.1055/s-0043-1773496Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents  |  Full text

Adamantane-based methacrylates are important monomers for the design of polymers used for the development of chemically amplified photoresists. Herein, we present the selection of reaction conditions for obtaining of 2-ethyladamantan-2-yl methacrylate, 2-methyladamantan-2-yl methacrylate, adamantan-1-yl methacrylate, and 3-hydroxyadamantan-1-yl methacrylate from adamantane derivatives and methacryloyl chloride. It is shown that the combination of pyridine as a solvent and base with 1,4-diazabicyclo[2.2.2]octane (DABCO) as a base allows reproducible preparation of the desired products with good yields. The results obtained provide valuable information for upscaling the synthesis of important products for the microelectronics industry.

Here, we have reported a visible-light-mediated organic photoredox-catalyzed difunctionalization of vinyl arenes via radical–radical coupling. A stabilized benzylic radical at the α-position is generated via the regioselective addition of phosphonyl radical at the β-position of the styrene. Subsequently, benzyl or allyl radical, generated via the deaminative pathway from the Katritzky salt, combines with the α-radical of the styrene to furnish the functionalised C–P and C–C bonds in a single reaction.

Chemical-capture-mediated sensing has had a great impact on proteomic research. Toward this end, we demonstrate the chemical trapping of BSA by the reactive formyl functionality of a newly developed fluorescent nucleoside probe, formylphenothiazine-labeled-2′-deoxyuridine. The probe is capable of trapping BSA via Schiff base formation leading to fluorescence ‘switch-on’ sensing with a large hypsochromic shift of ca. 100 nm. The α-amylase does not show any significant change in fluorescence response, demonstrating the efficiency of the probe in selective sensing of BSA. Docking studies suggest the preferential interaction of the phenothiazinylcarbaldehyde-labeled dU with the residual amino acids in site I of the BSA protein as compared to site II.

The catalytic dehydrogenation of methanol to give formaldehyde or formic acid, followed transfer hydrogenation and/or tandem (de)hydrogenation for the hydrogenation and C-methylation of carbonyls, offers advantages over traditional methods, including milder reaction conditions, improved safety, greater selectivity, and enhanced sustainability. This account provides a comprehensive overview of homogeneous catalysts reported for the transfer hydrogenation and C-methylation of various substrates, including ketones, chalcones, esters, and amides, using methanol as both a hydrogen donor and methylation source. We provide specific examples and mechanistic insights for each strategy, offering a thorough and concise overview of recent advancements from 2014 to 2024.1 Introduction2 Methanol Activation Strategies3 Hydrogenation of Carbonyls4 Methylation of Carbonyls5 Outlook and Summary