Refernces
10.1016/j.tet.2009.09.111
The study investigates the monoelectronic reduction mechanism of aromatic esters, with a particular focus on the synthetic utility of the toluate moiety in deoxygenation of alcohols and allylation of ketones. It also explores the use of aromatic esters as protective groups that can be easily removed. Chemicals used in the study include aromatic esters like toluates and benzoates, which serve as reagents and protective groups, and reducing agents such as samarium iodide (SmI2) and hexamethylphosphoramide (HMPA). These chemicals were employed to elucidate the reduction mechanism, develop novel synthetic reactions, and achieve selective deoxygenation and allylation reactions. The study also involved electrochemical techniques to perform metal-free reactions and deprotection of aromatic esters, demonstrating the versatility of toluates in organic synthesis and the potential of electrosynthesis for selective chemical transformations.
10.1002/anie.200460730
The study focuses on the highly diastereoselective nucleophilic addition of the anion derived from α-diazocarbonyl compounds to aromatic N-tosylimines, a reaction that is significant in organic synthesis. The researchers utilized a variety of chemicals, including α-diazocarbonyl compounds (1a-d) with chiral auxiliaries, N-tosylimines (2a-m), and bases such as lithium diisopropylamide (LDA), sodium hexamethyldisilazide (NaHMDS), and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). They also experimented with additives like LiCl, MgBr2, and HMPA to enhance stereoselectivity. The purpose of these chemicals was to explore the stereocontrol of the reaction, optimize reaction conditions, and synthesize syn- and anti-α-hydroxy-β-amino esters, which are important building blocks in organic chemistry. The study demonstrated that the diastereoselectivity of the reaction could be significantly improved by the use of HMPA, which likely disrupts ion pairing and allows the α-diazocarbonyl anion to react more efficiently. The results have implications for the synthesis of a range of organic compounds, particularly those containing α-hydroxy-β-amino acid derivatives.
10.1016/S0040-4039(00)87344-X
The study aimed to elucidate the mechanism of the condensation of enol dichloroacetylene with trichloroethylene to form α-dichlorovinyl ketone, which was previously unclear. The study concluded that the reaction proceeds via dichloroacetylene as an essential intermediate and the mechanism is elimination-addition. The fate of the initial adduct of dichloroacetylene and enol depends on the competition between unimolecular elimination of Cl- and bimolecular proton abstraction. The key chemicals used in the process include trichloroethylene, dichloroacetylene (ClC≡CCl), lithium diisopropylamide (LDA), hexamethylphosphoramide (HMPA) and lithium bis(trimethylsilyl)amide (LiN(SiMe3)2). The study also involved the use of deuterated trichloroethylene to study the isotope effect, supporting the proposed mechanism. This work has important implications for the synthetic scope of haloacetylene chemistry in the ethynylation and vinylation of enol systems.
10.1002/ejoc.201001061
The research investigates the impact of solvents and additives on the steric course of the [2,3]-Wittig rearrangement of chiral 1,3-diphenyl-1-propenyloxy-2-propen-1-yl carbanion and its derivatives. The purpose of the study was to understand how the configurational stability of chiral carbanions is influenced by solvents and additives, which is crucial for maintaining the optical purity of chiral centers during chemical reactions. The researchers concluded that the steric course of the rearrangement is significantly affected by the solvent and additive used, with the configurational stability of chiral carbanions being dependent on the solvent, reflecting the ratio of contact ion pairs (CIP) and separated ion pairs (SIP) associated with their solvated structures. Key chemicals used in the process include nBuLi, LDA, KHMDS, tetramethylethylenediamine (TMEDA), Me2NEt, hexamethylphosphoramide (HMPA), and various solvents such as Et2O, CPME, MTBE, DME, THF, and 1,4-dioxane. The study also utilized a range of substrates, including (S)-6a–g, which bear either an inductively anion-stabilizing halogen atom or a cyano group at the meta- or para-positions.
10.1021/jo00835a086
The study primarily focuses on the synthesis and properties of 3-azido-3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-allofuranose and its photolytic conversion to a ketone hydrate. The substrate, 3-azido-3-deoxy-1,2:5,6-di-O-isopropylidene-α-D-allofuranose, is obtained from 1,2:5,6-di-O-isopropylidene-3-O-(p-tolysulfonyl)-α-D-glucofuranose through nucleophilic displacement with sodium azide in hexamethylphosphoramide (HMPA). This reaction is faster in HMPA compared to dimethylformamide, reducing the reaction time from 15 days to 18 hours. The azide is then exposed to ultraviolet irradiation, leading to its complete conversion to a photoproduct, presumably an imine, which is subsequently converted to the ketone hydrate by refluxing with aqueous ether. The study also includes the synthesis of N-carbobenzoxyamino acid pentafluorophenyl esters as intermediates in peptide synthesis, highlighting their high reactivity and potential for use in peptide bond formation with minimal racemization. Additionally, the study explores the reduction of olefins using a mixture of sodium, hexamethylphosphoramide, and t-butyl alcohol, demonstrating its effectiveness in saturating carbon-carbon double bonds in various unsaturated compounds.
10.1016/S0040-4039(00)99135-4
The study investigates the asymmetric alkylation of arylacetic acid derivatives using binaphthyl esters as chiral auxiliaries. The researchers, Kaoru Fuji and colleagues, focused on synthesizing optically active 2-arylalkanoic acids, which are important due to their biological activity. They used (R)-binaphthyl esters of substituted and unsubstituted phenylacetic acids and alkylated them with various alkylating agents such as isopropyl iodide and isobutyl iodide. The reactions were carried out in tetrahydrofuran (THF) with lithium diisopropylamide (LDA) and hexamethylphosphoric triamide (HMPA) as reagents. The study demonstrated high diastereoselectivity, with the bulkiness of the alkylating agents significantly influencing the stereoselectivity. The phenolic hydroxyl group in the binaphthyl esters was found to be crucial for achieving high diastereoselectivity. The researchers also explored the effects of different substituents and reaction conditions on the yield and diastereomeric ratios of the products. The study provides insights into the mechanism of the reaction and its potential applications in the synthesis of biologically active compounds.
10.1016/S0040-4020(00)00353-7
The research investigates the cyclization reactions of ketoesters with an alkynylaryl substituent in the presence of samarium diodide. The purpose is to explore the competition between 8-endo-dig and 6-trig cyclizations, which lead to the formation of benzannulated cyclooctene or hexahydronaphthalene derivatives, respectively. The study finds that the outcome strongly depends on the substitution pattern of the starting ketoesters. Key chemicals include ketoesters (such as 3a-3h), samarium diodide (SmI2) as the reducing agent, and hexamethyl phosphoramide (HMPA) as a co-solvent. The research concludes that an unhindered alkyne is required for the 8-endo-dig cyclization to compete with the 6-trig cyclization, and that the reactions exhibit high stereoselectivity, producing predominantly trans-isomers for certain substrates. The findings provide valuable insights into the mechanisms and selectivity of these cyclization reactions, which have potential applications in the synthesis of complex organic compounds.
10.1016/0022-328X(83)85112-2
The research focuses on the oxidative cleavage of the silicon-carbon bond in alkenyltrifluorosilanes to yield carbonyl compounds, providing synthetic and mechanistic insights. The study aims to establish a new route for converting acetylenes to carbonyl compounds through hydrosilylation-oxidation, similar to the hydroboration-oxidation sequence. The researchers utilized m-chloroperbenzoic acid (MCPBA) as the oxidizing agent in dimethylformamide (DMF) at low temperatures to achieve the cleavage of the carbon-silicon bond, resulting in the formation of carbonyl compounds. The reaction's mechanism suggests a direct oxidative cleavage of the carbon-silicon bond, differing from the oxidation of trimethylsilyl counterparts which requires epoxidation and acidolysis. The study also explored the effects of solvent, reaction temperature, and oxidant quantity on the reaction's yield and course. Chemicals used in the process include alkenyltrifluorosilanes, MCPBA, DMF, and other solvents like tetrahydrofuran (THF) and hexamethylphosphoramide (HMPA), as well as DABCO-2H2O as an alternative oxidizing agent.
10.1016/0040-4020(82)80050-1
The research investigates the behavior of 9-bromo-10-methyl anthracene when treated with alkaline phenoxides and alkoxides in dipolar aprotic solvents. The purpose of the study was to understand the substitution reactions that occur under these conditions, focusing on the formation of both normal substitution products (NSP) and tele-substitution products (TSP). The researchers used various nucleophiles, including potassium phenoxide, sodium methoxide, and sodium ethoxide, in solvents such as dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and hexamethylphosphortriamide (HMPT). The study concluded that both types of ethers derived from a common unstable intermediate, 9-bromo-10-methylene-9,10-dihydroanthracene, which can undergo both normal and tele-substitution.
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