Refernces
10.1016/j.jorganchem.2020.121414
The research focuses on the development of a novel and convenient synthesis process for 1,3-bis(chlorodiorganosilyl)-cyclodisilazanes, which are important starting materials for preparing high-temperature-resistant elastomers. The synthesis involves an intermolecular dehydrochlorination of 1,3-dichloro-tetraorgano-disilazanes in the presence of a strong organic alkaline deacidification agent, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). The study compares different methods for preparing 1,3-dichloro-tetraorgano-disilazanes, including silyl group exchange reactions and equilibrium redistribution reactions, and examines the influence of various substituents on the reaction outcomes. The experiments utilize reactants such as hexamethylcyclotrisilazane, dimethyldichlorosilane, and diphenyldichlorosilane, among others, and employ techniques like 29Si NMR, 1H NMR, 13C NMR, FT-IR spectroscopy, and elemental analysis to characterize the synthesized compounds. The research also discusses the reaction mechanisms and provides detailed procedures for the synthesis of four different 1,3-bis(chlorodiorganosilyl)-tetraorganocyclodisilazanes, highlighting the advantages of using DBU as a deacidification agent for a one-step, mild, and efficient synthesis process.
10.1002/1522-2675(20010613)84:6<1504::AID-HLCA1504>3.0.CO;2-G
The research focuses on developing new base-labile protecting groups for the synthesis of oligoribonucleotides, addressing the challenges posed by the 2'-OH function in RNA assembly. The study involved synthesizing various carbonochloridates from hydroxy compounds, such as β-hydroxybenzenepropanenitrile and 2,2-bis(4-nitrophenyl)ethanol, which were then introduced at the 5'-O position of thymidine to create model nucleosides. Kinetic studies were conducted to evaluate the deprotection rates of these groups using bases like DBU, piperidine, and Et3N, with analyses performed via HPLC to determine half-lives and cleavage mechanisms. The results indicated that the newly synthesized protecting groups, particularly the 1-(2-cyano-1-phenylethoxy)carbonyl and 2-(4-nitrophenyl)ethoxycarbonyl, demonstrated promising compatibility for temporary protection during RNA synthesis.
10.1021/acs.joc.7b00512
The study titled "DBU-mediated Diastereoselective Aldol-type Cyanomethylation of Isatins" explores an efficient, metal-free approach to synthesizing 3-substituted 3-hydroxy oxindoles through DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) mediated addition of aryl acetonitrile to N-protected isatin under mild conditions. The researchers optimized the reaction conditions using various N-protected isatins and benzyl cyanides as substrates, achieving good yields and excellent diastereoselectivity. The study also includes DFT calculations to provide mechanistic insights into the aldol-type cyanomethylation process. The cyanomethylated adducts can be further transformed into advanced intermediates of natural product analogues, demonstrating the synthetic utility of this method.
10.1016/j.tetasy.2013.11.001
The study focuses on the total syntheses of both enantiomers of bacillamide C and neobacillamide A, natural products with bioactivity, and their optical activities. The researchers aimed to resolve the confusion regarding the absolute configurations of these metabolites, which have been derived from microorganisms growing in marine and terrestrial environments. They synthesized the compounds using a stereospecific route from D-(-)-alanine and compared the specific rotation of the synthesized compounds to those reported in literature. The results indicated that the absolute configurations previously proposed for bacillamide C and neobacillamide A should be revised to (S). This finding is significant for genomic studies of their biosynthesis and for the use of bacillamide C as a building block in bioactive cyclic peptides.
10.1016/S0957-4166(00)00327-X
The study focuses on the stereocontrolled cyclopropanation of enones derived from (S)-Garner’s aldehyde, aiming to synthesize 1,2,3-trisubstituted cyclopropanes with potential biological activities. The researchers utilized sulfonium ylides, specifically ethyl (dimethylsulfuranylidene)acetate (EDSA), generated in situ from ethyl dimethylsulfonium acetate bromide and DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), to react with enones 5 derived from (S)-Garner’s aldehyde in toluene. The major isomer produced from this reaction was found to have the configuration 2R,1’S,2’S,3’S. The study also explored the synthesis of a 3-benzyl analogue of the CCG family compounds, which are known for their biological significance. Various enones, sulfonium ylides, and reaction conditions were investigated to assess the scope and diversity of the reaction, ultimately concluding that the reaction allows for the assembly of 1,2,3-trisubstituted cyclopropanes with great diversity, potentially leading to the synthesis of biologically important compounds such as CCG analogues.
10.1055/s-0029-1218711
The study presents an efficient one-pot synthesis method for oxime ethers from alcohols using triphenylphosphine and carbon tetrachloride. The process involves the O-alkylation of oximes with various structurally diverse alcohols in the presence of catalytic amounts of tetrabutylammonium iodide and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in refluxing acetonitrile. The chemicals serve specific roles: triphenylphosphine and carbon tetrachloride convert alcohols into alkyl halides, DBU acts as a base to activate the O-H bond in oximes, and tetrabutylammonium iodide functions as a phase-transfer catalyst. The synthesized oxime ethers are important in organic and medicinal chemistry, used for introducing functional groups into organic compounds and as key structural motifs in drugs. The study demonstrates high efficiency and selectivity, with primary alcohols being more reactive than secondary alcohols in O-alkylation, and the method predominantly yields O-alkyl ethers over nitrones. The study also includes semiempirical quantum-mechanic calculations to support the stability of the synthesized products, indicating a lower heat of formation for Z-isomers.
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