10.1002/ejic.201000802
The study focuses on the synthesis and investigation of ruthenium complexes bearing N-H acidic pyrazole ligands and their application in catalytic hydrogenation reactions. The researchers treated chelate ligands containing pyrazole groups with various ruthenium precursors to form complexes with protic N-H groups near the catalytically active ruthenium center. These complexes were characterized by spectroscopic methods and DFT calculations, and their structure and reactivity were analyzed. The study aimed to understand the role of the acidic N-H groups in metal-ligand-bifunctional hydrogenation, where a hydrido ligand and a proton from a protic group are transferred simultaneously. The catalytic performance of these complexes was evaluated through the hydrogenation and transfer hydrogenation of acetophenone, and the results were connected to the ligand's electronic and structural properties. The research provides insights into the design of efficient catalysts for hydrogenation reactions by leveraging the acidic N-H groups in pyrazole ligands.
10.1021/jo961653u
The study focuses on the total synthesis of (±)-dihydrokawain-5-ol, a unique natural product isolated from the kava plant (Piper methysticum). The synthesis begins with a highly diastereoselective iodocyclofunctionalization of α-allenic alcohols to produce vinyl iodo syn-vicinal diols. A key feature of the synthesis is the differentiation of the alcohol groups in the vicinal diols through selective monoprotection using methoxymethyl (MOM) ethers or silyl ethers, followed by further functional group manipulations. The work explores various regioselective monoprotection techniques, cyclization strategies, and the isomerization of intermediates to form the final dihydropyranone structure found in dihydrokawain-5-ol. The study exemplifies the challenges and solutions in synthesizing complex natural products with specific stereochemical requirements.
10.1016/j.tetlet.2008.05.112
The research presents a stereoselective synthesis of (2S,3S)-sa?ngol and its natural (2S,3R)-isomer from 3,4,6-tri-O-benzyl glycals. The key step in the synthesis involves a one-pot reduction of an azide, saturation of double bonds, and debenzylation under catalytic hydrogenation. The synthesis route leverages carbohydrate-based chiral pool starting materials to construct both stereocenters with good overall yields of 21% and 36%, respectively. Reactants used include 3,4,6-tri-O-benzylated glycals, which undergo Perlin hydrolysis and acetylation to form trans-enals. These are then subjected to Wittig reaction to yield trans dienes, which are further converted to the final products through a series of reactions involving sodium methoxide, mesyl chloride, sodium azide, and catalytic hydrogenation with palladium on carbon. Analyses used to characterize the synthesized compounds include spectral data such as infrared (IR), nuclear magnetic resonance (NMR), and high-resolution mass spectrometry (HRMS), which were found to be in good agreement with reported data of the natural materials.
10.1002/anie.201610387
The research focuses on the development of a stereodivergent coupling reaction between vinyl halides and boronic esters, enabling the highly stereoselective synthesis of either the E or Z alkene isomers from a single vinyl coupling partner. This process occurs without the need for a transition-metal catalyst and involves electrophilic selenation or iodination of a vinyl boronate complex, followed by a stereospecific syn or anti elimination. The experiments utilized a variety of reactants, including E-vinyl bromide, enantioenriched boronic esters, and reagents such as lithium–halogen exchange, sodium methoxide, and iodine. The analysis of the products involved techniques like NMR, HPLC, GC, and DFT calculations, which confirmed the stereospecificity and yields of the coupled products.
10.1139/V09-026
The study investigates the catalytic cleavage of RNA model compounds, specifically 2-hydroxypropyl aryl phosphates, by a dinuclear Zn(II) complex of bis[1,4-N1,N1’(1,5,9-triazacyclododecanyl)]butane in methanol and ethanol. The aim is to understand the catalytic efficiency and mechanism of these reactions under controlled pH conditions at 25°C. The chemicals used include the dinuclear Zn(II) complex as the catalyst, various 2-hydroxypropyl aryl phosphates as substrates, methanol and ethanol as solvents, and sodium methoxide and sodium ethoxide to control the pH. The study also involves other chemicals like Zn(CF3SO3)2 for catalyst preparation and tetrabutylammonium trifluoromethanesulfonate for inhibiting effects. The purpose of these chemicals is to facilitate the cleavage reaction, control experimental conditions, and provide insights into the catalytic activity and kinetics of the dinuclear Zn(II) complex on RNA model compounds, which can help in understanding enzyme mechanisms and potential applications in biotechnology and medicine.
10.1246/bcsj.55.3254
The study focused on a new synthetic method for a branched amino sugar, specifically methyl 2-amino-2,3-dideoxy-3-C-formyl-α-D-glucofuranoside-3'R,5-hemiacetal. The aim of this study was to develop a new method for the synthesis of branched amino sugars that could potentially be used as building blocks for the synthesis of alkaloids and β-lactam antibiotics. The main conclusion of the study was the successful synthesis of the target compound via skeletal rearrangement of N,O-phthalidesulfonyl derivatives without the need for external protecting groups. The process involved the use of various chemicals, including methyl 2-amino-2-deoxy-α-D-glucofuranoside, phthalidesulfonyl dichloride, sodium methoxide, and several other reagents for the synthesis of the derivatives. The researchers also noted the stereospecificity of the synthetic process and the formation of specific derivatives, which could aid in the synthesis of nitrogen-containing natural products.
10.1016/0223-5234(87)90275-3
The research focuses on the synthesis of a series of nitro-naphtho[1,2-b]furans with methoxy groups on the external homocycle. The purpose of this study is to synthesize and characterize these compounds, which are of interest due to their potential mutagenic and carcinogenic properties, similar to the previously studied methoxy-7 nitro-2 naphtho[2,1-b]furane (R 7000). The researchers used methoxy-tetralones as starting materials, converting them into ortho-hydroxylated naphthaldehydes via a series of chemical reactions involving ethyl formate, sodium methoxide, and dichlorodicyanobenzoquinone. These intermediates were then treated with bromonitromethane and potassium carbonate, followed by dehydration in acetic anhydride to yield the desired nitro-naphtho[1,2-b]furans. The study concludes that this synthetic method is efficient, with overall yields ranging from 40% to 70% for the different compounds. The synthesized compounds are obtained in sufficient quantities for further biological testing, which will be detailed in subsequent studies.
10.1016/j.tet.2007.03.116
The research focuses on the novel synthesis of 2-aminopentanedinitriles from 2-(bromomethyl)aziridines and their subsequent transformation into 2-imino-5-methoxypyrrolidines and 5-methoxypyrrolidin-2-ones. The study explores an unprecedented reaction mechanism involving base-induced ring opening of intermediate 2-(cyanomethyl)aziridines into allylamines, followed by migration of the double bond towards aldimines via enamine intermediates. The synthesized aminopentanedinitriles serve as precursors for the preparation of glutamic acid derivatives, which are significant in the central nervous system as excitatory neurotransmitters. The experiments utilized reactants such as 1-arylmethyl-2-(bromomethyl)aziridines, potassium cyanide in DMSO, and sodium methoxide in methanol. The analyses included column chromatography for purification, and various spectroscopic techniques such as NMR, IR, and MS for structural characterization and confirmation of the synthesized compounds.
10.1002/cber.19971300710
The research focuses on the synthesis and characterization of mono- and bicyclic organometallic ring systems containing exocyclic C=C and C=S bonds. The purpose of the study was to develop new routes to metal-containing ring systems with both exocyclic C=CH2 and C=S bonds, convert these species to bicyclic dithiolenecobalt complexes, and investigate the formal insertion of activated alkynes into the C=CH2 bond. The researchers prepared cobaltaheterocycles from imino-acylcobalt compounds using CS2/NaOCH3 or K[S2CNMe2] and explored their reactions with various electrophilic substrates, such as HBF4, [OMe3]BF4, and C2(CO2R')2 (R' = Me, Et). They found that protonation and methylation reactions of the initially formed heterocycles and insertion products occur at different sites, likely due to the hardness and softness of the reacting centers. The conclusions of the research highlight the successful synthesis of novel bicyclic dithiolenecobalt complexes and the insight into the reactivity of these complexes towards electrophilic addition and insertion reactions.
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