Synlett

We report an unprecedented synthesis of bis(pyrazolo[1,5-a]pyrimidin-3-yl)methanes, a new class of di(hetaryl)methanes, from pyrazolo[1,5-a]pyrimidines by using DMSO as a C1 synthon (methylene source). The transformation is mediated by sodium metabisulfite (Na2S2O5), which plays a crucial role in the presence of acetic acid as a promoter. A wide variety of bis(pyrazolo[1,5-a]pyrimidin-3-yl)methanes were synthesized in moderate to good yields of up to 90%. Mechanistic studies suggested that the reaction follows an ionic pathway, probably involving a methyl(methylene)sulfonium ion as an active electrophilic species formed in situ by the reaction of DMSO with Na2S2O5.

Tellurium is now recognized as a ‘technology-critical element’ that is quickly being used in innovative applications. The chemistry of organotellurium ligands has improved rapidly during the last three decades. Because of their enhanced accessibility and the possibility that they would display significantly different properties than their sulfur counterparts, these ligands of heavier chalcogens have sparked considerable attention. The next sections will go through the various tellurium ligands and associated transition-metal complexes. Organochalcogen ligands are exceedingly flexible ligands that may react with nearly any transition metal to form a wide range of compounds, including multidentate ligands.Tellurides of various metals have lately been investigated for potential use in storage devices, solar cells, piezoelectric, medical applications, electronics, photothermal treatment, nanoplatelets, nanocrystals, catalysis, and other fields. Researchers are interested in metal chalcogenide heterostructures because of their improved charge transport and synergistic optoelectronic and catalytic properties. A sensor for various metals based on Te electrodes and a donor ligand are used to generate electrical signals and identify different metals. Due to the scarcity of tellurium, metal telluride nanocrystal heterostructures have received less attention than metal sulfide and metal selenide nanocrystal heterostructures.1 Introduction2 Tellurenated Compounds of Zwitterionic Nature3 Synthesis of Tellurenated Ligands and Complexes4 Catalytic Application and and Suzuki–Miyara Coupling5 Tellurenated Sensors for Metal-Ion Sensing5.1 Tellurium-Ion Detectors5.2 Drawbacks/Catalyst Poisoning5.3 Disadvantages5.4 Advantages and Future Prospects6 Conclusions

The Birch reduction has found a renaissance during the last two decades. In this Synpacts article a short summary of selected recent synthetic applications will be provided. 1,4-Cyclohexadienes, which are formed by Birch reduction in one step, are suitable precursors for radical reactions and are used as surrogates for difficult-to-handle substances. Their rearomatization under acidic conditions offers easy access to selectively alkylated arenes. Additionally, the Birch reduction of benzoic acids and subsequent trapping afford spiro compounds in high yields. Very recently, it was shown that 1,3-cyclohexadienes are directly available by Birch reduction in a one-pot reaction as well.1 Introduction2 Rearomatizations3 Synthesis of Spiro Compounds4 Synthesis of 1,3-Cyclohexadienes5 Conclusion

Reactions of bis(cyclopentadienyl)titanacyclopentenes with BiI3 gave coupling products of one Cp ligand and the alkenyl carbons in moderate yields. An NMR study of the tetracyanoethylene (TCNE) adduct of the product showed that the coupled Cp ring and the alkenyl carbons were connected by one carbon–carbon double bond. This is in sharp contrast to coupling reactions of one Cp ligand with the diene moiety in bis(cyclopentadienyl)titanacyclopentadienes, where two carbon–carbon single bonds were formed between those two components to give dihydroindenes or spiro compounds.

This account describes the latest developments on 3d-metal-catalyzed single-electron-transfer (SET)-induced strategies that use carboxylic acids and their synthetic equivalents as substrates. In general, 3d-metal-promoted SET-mediated transformations of free carboxylic acids proceed readily via the formation of carboxylate radicals, whilst those of carboxylic acid equivalents, bearing an N-donor substituent, proceed via the formation of α-carbo radicals. The advantages of these strategies combine the low-cost of carboxylic acid starting materials and 3d metal catalysts with the possibility of realizing structurally diverse ranges of compounds in an atom- and step-economic manner. Developments primarily achieved by our group and a few by other researchers on this topic are discussed in this account.1 Introduction2 Mechanistic Considerations of 3d-Metal-Catalyzed SET-Mediated Transformations3 Developments Based on SET-Mediated Transformations of Carboxylic Acids4 Developments Based on SET-Mediated Transformations of Carboxylic Acid Equivalents5 Conclusion and Outlook

This report describes a Ru(II)-catalyzed C–H allylation of N,N-dialkylthiobenzamides with allyl methyl carbonate. The reaction is carried out using [RuCl2(p-cymene)]2 in the presence of Cu(OAc)2 and Ag2O. This method represents the first example of a Ru-catalyzed C–H allylation directed by a sulfur-containing group. As a further advantage, the method is performed in sustainable and ecofriendly MeCN as the solvent.

6-Hydroxy-8-chlorooctanoate ethyl ester, an intermediate of α-lipoic acid, was synthesized via a chemoenzymatic method. High-throughput screening revealed that keto reductase HGD-1 could effectively catalyze the preparation of 6-hydroxy-8-chlorooctanoate ethyl ester, achieving a substantial conversion rate. The reaction conditions were optimized subsequently, the parameters for the complexation reaction were established as follows: a weight of AlCl3 1.8 times that of the substrate; a reaction time of 4 h; a temperature range of 20–25 °C. The parameters for the enzyme-catalyzed reaction were as follows: a temperature range of 25–30 °C; a reaction time of 4 h; a solution pH of 6.5–7.5; a substrate concentration of 50 g/L; concentrations of keto reductase HGD-1, coenzyme glucose dehydrogenase, and nicotinamide adenine dinucleotide phosphate of 3 g/L, 4 g/L, and 0.05 g/L, respectively. Under these optimal conditions, the substrate conversion rate exceeded 95%, and 92% yield of 6-hydroxy-8-chlorooctanoate ethyl ester is obtained, suggesting a viable, eco-friendly method for synthesizing α-lipoic acid, and it provides a green process route for the industrial production of α-lipoic acid.

We synthesized diarylated 10-(1,3-dithiol-2-ylidene)anthracene-9-(10H)-one derivatives, which serve as important precursors of unsymmetrical arylated TTFAQs, via the palladium-catalyzed direct C–H arylation. Unsymmetrical diarylated TTFAQs were synthesized by the Horner–Wadsworth–Emmons reaction using diarylated 10-(1,3-dithiol-2-ylidene)anthracene-9-(10H)-one as the starting materials. Additionally, we have successfully synthesized unsymmetrical tetraarylated TTFAQs by a second palladium-catalyzed C–H arylation of diarylated TTFAQs.

Cyclobutane derivatives are important motifs in natural products and bioactive compounds. Owing to their inherent strain, the asymmetric synthesis of cyclobutanes remains a formidable challenge. With the development of various stereospecific transformations of alkylboronic esters, chiral cyclobutylboronates are expected to serve as promising synthetic intermediates for accessing chiral cyclobutane derivatives. However, obtaining highly enantioenriched cyclobutylboronates poses a daunting task in the field of organic synthesis. In this context, we highlight recent significant advances in the synthesis of chiral cyclobutylboronates.1 Introduction2 Enantioselective Borylation of Cyclobutenes3 Enantioselective Borylation of Cyclobutanes4 Other Methods5 Conclusions

This study introduces an efficient, environmentally friendly, and sustainable method for synthesizing N-acylhydrazone analogues by engaging isoniazid in a condensation reaction with variously substituted benzaldehydes. The deep-eutectic solvent (ZnCl2/urea) employed in this study acted not only as a solvent but also as a catalyst to facilitate the synthesis of the target compounds within two to six minutes without the requirement of any lengthy purification techniques. The synthetic protocol is operationally simple and offers other remarkable advantages such as a short reaction time, good to excellent yields, a scalable protocol, and a recyclable and reusable catalyst. Additionally, green metrics calculations suggest the present method to be environmentally benign. Finally, the frontier molecular orbitals and the global reactivity parameters of the synthesized compounds were predicted by using density functional theory calculations.