10.1016/j.tetlet.2008.05.037
The study presents a rational design of bis(thiourea) cocatalysts to accelerate the Morita–Baylis–Hillman (MBH) reaction, a C–C bond forming reaction known for its sluggishness. By applying electronic structure calculations, the researchers identified key transition states and designed catalysts that could stabilize these states through hydrogen bond recognition of both nucleophile and electrophile. The cocatalysts were synthesized and tested, demonstrating significant acceleration of the MBH reaction between cyclohexenone and 4-fluorobenzaldehyde. The study shows that the designed cocatalysts, particularly one with an o-xylyl bridge, were much more effective than the previously reported bis(thiourea) cocatalyst, nearly tripling the reaction rate. The findings underscore the potential of computational methods in designing organic catalysts that utilize hydrogen bonding for enhanced reactivity.
10.1055/s-2004-831250
The study presents an efficient method for synthesizing esters and thioesters from corresponding carboxylic acids using Tetramethylfluoroformamidinium hexafluorophosphate (TFFH) as a coupling reagent. The research details the preparation of N-acyl-dithiocarbamates from carboxylic acids and 1,3-thiazolidine-2-thione with TFFH. It highlights TFFH's advantages over traditional reagents like Dicyclohexylcarbodiimide (DCC), including higher reactivity, fewer byproducts, and lower toxicity. The study also demonstrates the chemoselective acylation of dithiocarbamates using TFFH, which is beneficial for preparing aldehydes from carboxylic acids. The results show that TFFH is effective for a wide range of substrates, including those with sensitive functional groups, and can be used under mild conditions with high yields, making it a valuable reagent in organic synthesis.
10.1021/acs.organomet.8b00635
The research discusses the synthesis and characterization of first-row late 3d transition metal silylene complexes supported by trisPhosphinoborate ligands, with the aim of understanding their electronic structures, reactivity patterns, and potential applications in hydrosilylation catalysis. The study focused on complexes of iron, cobalt, and nickel with the [BP3 R] ligand scaffold, where R represents different substituents. Key chemicals used in the process include [BP3 Ph]NiCl, [BP3 Pr]CoCl, (THF)2LiSiHMes2, CySiH3, and 4-dimethylaminopyridine (DMAP). The researchers discovered that α-H migration steps were effective in forming metal-silylene complexes, and that anionic silyl sources and hydrosilanes could be used as precursors for silylene-type ligands. They also observed residual M?H···Si interactions in some complexes, emphasizing the importance of hydride ligands in stabilizing reactive silylene moieties. The [BP3 iPr] ligand was found to enable access to silylene and alkyl complexes that could not be generated with the less sterically protecting [BP3 Ph] ligand. The study concluded that the ancillary ligands significantly influence the reactivity of 3d-metal silylene complexes, and future work will focus on this influence.
10.1021/jo030367x
The study presents an efficient method for synthesizing carboxylic esters and lactones using 2-methyl-6-nitrobenzoic anhydride (MNBA) as a dehydrating reagent. The key chemicals involved include carboxylic acids and alcohols, which are the starting materials for esterification, and MNBA, which reacts with carboxylic acids to form mixed anhydrides. Triethylamine acts as a base to neutralize the acid byproduct, while 4-(dimethylamino)pyridine (DMAP) serves as a catalyst to promote the reaction. The study demonstrates that this method allows for the production of carboxylic esters and lactones in high yields and with high chemoselectivity at room temperature. The protocol is particularly advantageous for synthesizing compounds that are sensitive to acidic conditions and can be applied to a wide range of substrates, including those with acid-sensitive protective groups. The study also highlights the successful application of this method to the synthesis of erythro-aleuritic acid lactone and the eight-membered-ring lactone moiety of octalactins A and B, showcasing its utility in the preparation of complex natural products.
10.1016/j.tetlet.2003.11.133
The study presents a concise synthesis method for a novel class of homochiral aromatic amino acid surrogates, featuring tetrahydroindazole or benzisoxazole systems. These surrogates were synthesized through the acylation of cyclic 1,3-diketone by the side-chain carboxyl functionality of specific amino acid precursors, followed by a regioselective condensation with hydrazine, N-benzylhydrazine, and hydroxylamine. The synthetic strategy is versatile, allowing for the creation of structurally diverse derivatives. These novel amino acids can be efficiently incorporated into proteins and have potential applications in imparting unique properties to biological peptides. The study also includes the synthesis of Na-Fmoc-protected derivatives, which are useful for solid-phase peptide assembly, and the exploration of the stereochemistry integrity of the homochiral starting material through chemical transformations. The synthesized amino acids offer opportunities as structural surrogates of tryptophan and as building blocks for designing molecular probes.
10.1016/j.tetlet.2011.07.078
The research focuses on the stereoselective synthesis of the peptide moiety of jamaicamides, which are marine natural products with sodium channel blocking properties. The synthesis begins with natural amino acids, L-alanine and N-Boc-β-alanine, and utilizes Meldrum's acid as a key reactant. The researchers detail the preparation of two segments of the peptide: the pyrrolidone ring and the N-Boc-β-methoxy enone carboxylic acid. Various reagents such as EDC·HCl, DMAP, NaBH4, and LiHMDS are used in a series of reactions including condensation, reduction, and amide bond formation. Analytical techniques likely employed, though not explicitly mentioned in the paragraph, include NMR spectroscopy and mass spectrometry for compound characterization. The study also discusses alternative routes and yields for different steps, aiming to optimize the synthesis process.
10.1021/acs.orglett.8b03567
The study presents a method for the stereoselective preparation of α-C-vinyl and -aryl glycosides through nickel-catalyzed reductive coupling of glycosyl halides with vinyl and aryl halides. The researchers utilized a variety of chemicals, including acetyl-protected glucosyl bromide, E-(2-bromovinyl)benzene, pyridine, N,N-dimethyl aminopyridine (DMAP), MgCl2, Zn, and various vinyl and aryl halides. These chemicals served as substrates, catalysts, and ligands to achieve high α-selectivities for C-glucosides, galactosides, maltoside, and mannosides. The purpose of these chemicals was to develop a controlled method for the synthesis of α-C-vinyl-glucosides and α-C-aryl glucosides, which are important in the field of organic chemistry and have potential applications in pharmaceuticals and materials science. The study also explored the effects of different reaction conditions, ligands, and substrate structures on the stereoselectivity of the reaction products.
10.1039/c39860001524
The research details a novel method for oxygen-to-carbon ester migration in the benzofuranone ring system, catalyzed by 4-(N,N-dimethylamino)pyridine (DMAP). The purpose of this study was to address the challenge in synthetic chemistry of regioselective carbon acylation of enolates, particularly those that are highly delocalized, as the kinetically-formed oxygen-acylated products usually predominate. The researchers reported a method that quantitatively rearranges the initially-formed enol carbonate to its carbon-acylated isomer, using DMAP as a catalyst. The benzofuranones, which have a wide spectrum of pharmacological activity, were the focus of this study due to their importance in the synthesis of potential anti-neoplastic agents. Key chemicals used in the process included sodium hydride in dimethylformamide (DMF) for deprotonating 3-phenyl-2(3H)-benzofuranone, ethyl chloroformate for the formation of enol carbonate, and DMAP for catalyzing the rearrangement to the C-acylated ester. The study concluded that DMAP could effectively catalyze the carbon acylation, leading to the desired C-acylated ester, and that this reaction was general for several alkyl chloroformates.
10.1021/acs.orglett.1c01720
The study presents an efficient method for the trifluoromethylation of benzoic acids using TMSCF3 (trimethylsilyl trifluoromethane) to produce aryl trifluoromethyl ketones. The reaction involves anhydrides as in situ activating reagents, with trifluoroacetic anhydride (TFAA) and 4-dimethylaminopyridine (DMAP) playing crucial roles in activating the carboxylic acids and facilitating nucleophilic addition. CsF (cesium fluoride) is used to enhance the yield of the desired products. The reaction is conducted in PhOMe (anisole) solvent under nitrogen at 120 °C for 15 hours. The study demonstrates a wide substrate scope, including various carboxylic acids with different functional groups, and shows high functional group tolerance. Notably, bioactive molecules such as adapalin, probenecid, and telmisartan can also be trifluoromethylated using this method, highlighting its potential in drug design and development. The reaction conditions are relatively mild, and the process is scalable, making it a practical and environmentally benign approach for synthesizing aryl trifluoromethyl ketones.
T,
C,
T+
