Refernces
10.1021/ol006146k
The research focuses on the asymmetric Wolff rearrangement reactions using α-amino-α'-methyl-α'-diazoketones to synthesize α-methyl-β-amino acid esters with good stereoselectivity. The study examines factors influencing the stereochemistry, such as steric effects and temperature dependence. The reactants include α-alkylated-α-diazoketones prepared from α-amino acids through a two-step process involving diazomethane coupling and anionic alkylation reactions. The Wolff rearrangement reactions are initiated using UV light at -78 °C in dichloromethane to generate intermediate ketenes, which are then trapped with nucleophiles like alcohols to yield α-methyl-β-amino acid derivatives. The stereochemistry of the major diastereoisomer was determined to be anti through single-crystal X-ray crystallographic analysis and chemical correlations. The experiments also revealed that the steric size of substituents and the nitrogen protecting group significantly affected the diastereomeric ratios, with Boc protecting group showing higher stereoselectivity than Fmoc. Temperature was found to be a crucial factor, with better diastereoselectivity at lower temperatures. The analysis included 1H NMR, HPLC, and X-ray crystallography to determine the ratios and stereochemistry of the products.
10.1016/j.tetlet.2011.05.149
The research focuses on the synthesis of N-vinyl 2,2-bisphosphonoaziridines from 1,1-bisphosphono-2-aza-1,3-dienes using diazomethane as the key reactant. The study explores the effects of substituents at the 4-position of the 1,1-bisphosphono-2-aza-1,3-dienes on the reaction outcomes, leading to either 1-(ethenylamino)-2-phosphonoethenylphosphonates or mixtures of these compounds along with 2-imino-2-phosphonoethylphosphonates as side products. The experiments involved treating various 1,1-bisphosphono-2-aza-1,3-dienes with diazomethane in Et2O at room temperature, with reaction times and yields detailed in the article. The reaction products were analyzed using 31P NMR, 1H NMR, and 13C NMR spectroscopy, along with IR spectroscopy and mass spectrometry for compound characterization, and elemental analysis to confirm the composition of the synthesized compounds. The research also investigated the reaction mechanism and the influence of reaction conditions such as light and temperature on the formation of N-vinyl 2,2-bisphosphonoaziridines and enaminophosphonates.
10.1002/chem.200802052
The study focuses on the palladium-catalyzed cyclopropanation of alkenyl silanes using diazoalkanes, exploring the mechanism and efficiency of this reaction in organic chemistry. The researchers used Pd(OAc)2 as a catalyst, diazomethane (CH2N2), diazoethane, and diazobutane as diazo compounds, and a variety of alkenyl silanes as substrates. The purpose of these chemicals was to investigate the formation of silyl cyclopropanes, assess the diastereoselectivity of the cyclopropanation, and gain insights into the active species and resting state of the catalyst. The study provides evidence for a Pd0 mechanism and suggests that a Pd0(alkenyl silane)3 complex is the resting state in the catalytic cycle. The findings have implications for the development of asymmetric versions of this reaction and contribute to the understanding of palladium-catalyzed cyclopropanation reactions.
10.1021/jo00363a050
The research focuses on the synthesis and characterization of chemical adducts formed by the reaction of diazomethane with 7-chloronorbornadiene, as well as the exploration of the Hanessian-Hullar reaction in carbohydrate chemistry. The purpose of the study was to investigate the selectivity and specificity of 1,3-dipolar cycloadditions involving diazoalkanes and 7-substituted norbornadienes, challenging previous claims of stereospecificity in such reactions. The researchers found that the reaction was not stereospecific, forming both endo,syn and endo,anti isomers, and that diazomethane and diazoethane formed a variety of adducts with different structures. They also discovered a new reactive intermediate formed by triflate rearrangement, which has potential for carbohydrate synthesis. The chemicals used in the process include diazomethane, 7-chloronorbornadiene, ether-hexane for TLC analysis, and various norbornadienes and 1,3-dipoles for studying selectivity and specificity in reactions. The conclusions drawn from the research indicate that while selectivity in these reactions can be high, specificity is never found, and the researchers are conducting further systematic studies on related reactions to be reported later.
10.2174/157017809790443005
The study presents a new method for preparing N-tosyl-L-phenylalanine chloromethyl ketone (TPCK), an irreversible serine protease inhibitor, without using toxic and explosive diazomethane. L-Phenylalanine is first tosylated to form N-tosyl-L-phenylalanine, which is then converted into its 4-nitrophenyl ester using DCC and DMAP. This ester reacts with dimethylsulfoxonium methylide, generated from trimethylsulfoxonium iodide and potassium tert-butoxide, to form a sulfur ylide. The sulfur ylide is subsequently treated with lithium chloride and methanesulfonic acid to produce the chloroketone, TPCK. This method achieves an overall yield of 36% and avoids the use of hazardous diazomethane, providing a safer and practical synthesis route.
10.1016/j.ejmech.2016.06.014
The research focuses on the synthesis and antimicrobial activity of a novel class of mono and bis heterocycles, including styryl, pyrrolyl, and pyrazolyl sulfonylmethyl-1,3,4-oxadiazolyl/thiadiazolyl amines. The study utilizes Z-styrylsulfonylacetic acid as a synthetic intermediate and employs various synthetic methodologies to prepare these compounds. The antimicrobial activity of these synthesized compounds was then evaluated against different bacterial and fungal strains. The reactants used in the synthesis encompass semicarbazide, thiosemicarbazide, POCl3, tosylmethyl isocyanide, sodium hydride, diazomethane, and chloranil, among others. The synthesized compounds were characterized using techniques like infrared (IR) spectroscopy, nuclear magnetic resonance (NMR), high-resolution mass spectrometry, and elemental analysis. The antimicrobial activity was assessed using the agar well diffusion method and broth dilution test to determine the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and minimum fungicidal concentration (MFC). The findings revealed that mono heterocyclic compounds, particularly 5-(4-chlorostyrylsulfonylmethyl)-1,3,4-thiadiazol-2-amine (5c), exhibited superior antimicrobial activity against certain bacteria and fungi compared to the bis heterocyclic systems.
10.1016/j.bmcl.2005.05.116
The research investigates the impact of lipophilic and hydrogen-bonding interactions in the P3 region on the potency and selectivity of valine aspartyl ketones as inhibitors of caspase 3, an enzyme involved in apoptotic cell death. The study aims to develop more potent and selective caspase 3 inhibitors for potential use in treating degenerative diseases. Key chemicals used include Fmoc-aspartic acid β-t-butyl ester, diazomethane, benzyl mercaptan, and various carboxylic acids for solid-phase synthesis. The researchers found that introducing a hydroxyl group alpha to the P3 carbonyl significantly increased potency and selectivity, suggesting a hydrogen-bonding interaction with the enzyme. They also explored the effects of different substituents on the phenyl ring, concluding that optimal binding required a balance between hydrogen bonding and lipophilic interactions. The most potent compound identified was a mandelic acid derivative with an iodo substituent, which also offered advantages for further development as a cell-permeable radioactive tool.
