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.
10.1021/ol0502026
The study by Scott T. Handy and Duncan Omune investigates the reductive cyclization of tethered bis-enones with one-carbon tethers, focusing on the influence of reaction conditions and α-substitution on the cyclization pathway. They found that the cyclization products, either pinacol or hydrodimerization-type, are highly dependent on these factors. The researchers synthesized three cyclization substrates and explored their reductive cyclization under electrochemical conditions and using samarium diiodide. They observed that electrochemical conditions favored pinacol-type products, while samarium diiodide favored reductive cyclization products. The study suggests that chelation and steric effects play a crucial role in determining the cyclization pathway, with Lewis acidic metals promoting pinacol formation and non-chelatable metals favoring reductive cyclization. This mechanistic understanding was further supported by experiments using magnesium in methanol, which resulted in pinacol products. The findings highlight the importance of reaction conditions in controlling the cyclization outcome and provide insights into the mechanism of reductive cyclization reactions.
10.1007/s11172-007-0243-5
The research presents a novel method for synthesizing 6-R-3-arylazo-1H-pyridazin-4-ones from difluoroboron chelates of 1,3-diketones. The study is based on the reactivity of the methyl group in these chelates with two equivalents of a diazonium salt. The synthesis involves a two-step process: first, the reaction of difluoroboron complexes of ?-diketones with diazonium salts at low temperatures to form dark red crystalline intermediates, followed by their decomposition upon refluxing in a pyridine-butanol mixture to yield the final 3-arylazo-1H-pyridazin-4-one derivatives. Acetylacetone and aroylacetones as the starting 1,3-diketones. Boron trifluoride etherate and tributyl borate for the preparation of difluoroboron chelates. The researchers utilized various spectroscopic techniques, including 1H and 13C NMR, IR, and mass spectrometry, to identify and analyze the structures of the synthesized compounds. The study also explored the possibility of structural isomers and confirmed the formation of the desired compounds through 2D NMR spectroscopy.
10.1016/S0040-4020(00)01008-5
The research focuses on the synthesis of spiroazabicycloalkane amino acid scaffolds, which serve as reverse-turn inducer dipeptide mimics. These conformationally constrained molecules are designed to mimic Ala-Pro dipeptide units or more generally, the central (i+1 and i+2) residues of β-turns in peptide chains. The methodology involves a series of chemical reactions starting from known compounds, utilizing reagents such as LiEt3BH, Ac2O, allyltributyl tin, BF3.Et2O, OsCl3, and NaBH4, among others, to produce the desired scaffolds. The experiments include hydrogenolysis, hydrolysis, protection of nitrogen atoms, dihydroxylation, oxidation, and olefination steps. The analyses used to characterize the intermediates and final products encompass 'H and 13C NMR spectroscopy, elemental analysis, mass spectrometry, and optical rotation measurements. Single crystal diffraction analysis was also performed to secure the configuration of the diastereoisomeric alcohols. The study successfully demonstrates a practical approach to synthesize these constrained scaffolds, which could potentially improve peptide-receptor affinity by interacting with hydrophobic pockets, thereby enhancing the metabolic stability of peptides.
10.1016/0040-4020(86)80014-X
The research focuses on the synthesis of oxygen-containing heterocycles with a vinylidene exocyclic group, specifically vinylidyne-5 dioxanes-1,3, through organosilicon chemistry. The purpose of the study is to develop a regiospecific method for the preparation of these compounds using α-silyloxypropargyltrimethylsilanes, which react with aliphatic aldehydes in a one-pot reaction. The researchers found that this method effectively yields a variety of alkyl-substituted 5-vinylidene-1,3-dioxanes with good yields and purity. The chemicals used in the process include α-silyloxypropargyltrimethylsilanes, aliphatic aldehydes with primary or secondary alkyl groups, and Lewis acids such as TiCl4 and BF3.O(C2H5)2 as catalysts. The study concludes that the presence of a Lewis acid facilitates the regiospecific reaction of α-silyloxypropargyltrimethylsilanes with aliphatic aldehydes, leading to the formation of diversely substituted vinylidyne-5 dioxanes-1,3 in a single step and with good yields.
10.1021/ja00385a038
The research involves two separate studies. The first study focuses on the total synthesis of the 16-membered ring macrolide antibiotic tylonolide hemiacetal. Key chemicals used in this research include chiral bicyclo[2.2.1]heptenol, which was elaborated into the C(3)-C(9) and C(11)-C(17) fragments through a series of complex organic reactions involving reagents such as benzyl chloride, boron trifluoride etherate, lithium aluminum hydride, and m-chloroperbenzoic acid. The synthesis also utilized various solvents like methylcyclohexane and tetrahydrofuran, and involved steps like benzoylation, olefin inversion, and allylic oxidation to ultimately achieve the coupling of the fragments and the formation of the 16-membered macrolide ring. The second study investigates the photochemical formation of tetracarbonyl(4,4’-dialkyl-2,2’-bipyridine)metal from hexacarbonylmetal using rapid-scan Fourier transform infrared spectroscopy. Chemicals such as W(CO)6, 4,4’-(n-C19H39)2-2,2’-bpy, and 2-phenylpyridine were used to observe the formation of monodentate intermediates in the reaction. The study provides direct infrared spectral evidence for the formation of these intermediates, highlighting the role of CO and the bipyridine ligands in the photochemical process.
10.1002/cplu.201900317
The research aims to design, synthesize, and characterize a new acceptor-donor-acceptor (AD-A) semiconductor, BDY-Ph-2T-Ph-BDY, which features a central phenyl-bithiophene-phenyl p-donor and BODIPY p-acceptor end-units. The purpose is to develop a solution-processable n-channel semiconductor with enhanced fluorescence emission for next-generation optoelectronics. The study concludes that BDY-Ph-2T-Ph-BDY exhibits an optical band gap of 2.32 eV, highly stabilized HOMO/LUMO energies (-5.74 eV/-3.42 eV), and a D-A dihedral angle of ~66°. It shows good fluorescence efficiency (FF = 0.30) and n-channel OFET transport characteristics (μe = 0.005 cm2/V·s; Ion/Ioff = 104-105), representing a significant improvement in fluorescence quantum yield compared to previous BODIPY semiconductors. This work demonstrates the potential of BDY-Ph-2T-Ph-BDY for high-performance optoelectronic applications. 4-Bromobenzaldehyde is used as a starting material to introduce the phenyl group into the BODIPY structure. N-Ethylpyrrole acts as a building block for the BODIPY core. P-Chloranil (2,3,5,6-Tetrachloro-1,4-benzoquinone) is used as an oxidizing agent in the synthesis process.
10.1021/jo0013711
The research focuses on the asymmetric synthesis of (S)-CPPG, a selective antagonist for group III metabotropic glutamate receptors (mGluRs), which are important in studying neurotransmission mechanisms. The synthesis begins with (R)-4-benzoxyphenylglycine and involves several steps including protection of the amino group, formation of trans-oxazolidinone, introduction of a dicarbon functional group, and cyclopropanation. Key reactants include methyl chloroformate, benzaldehyde dimethyl acetal, boron trifluoride etherate, and various catalysts for cyclopropanation. The process involves recrystallization, HPLC, and 1H NMR for analysis, and culminates in the production of (S)-CPPG with a final yield of 99% after purification. The study also mentions the biological evaluation of the synthesized compound, indicating ongoing research into its physiological effects.
10.1055/s-0028-1087672
The research focuses on the development of a flexible and highly regio- and diastereoselective approach to synthesize methyl 5-alkyltetramate derivatives, which are key frameworks in numerous bioactive natural products. The method involves regioselective Grignard reagent additions to 3-methoxymaleimides, followed by diastereoselective reductive dehydroxylation of the resulting N,O-acetals. The experiments utilized various Grignard reagents, such as methyl magnesium iodide and n-butyllithium, and reagents like boron trifluoride etherate and triethylsilane for the reductive dehydroxylation step. The study also explored the use of (S)-phenylglycinol as a chiral auxiliary in the synthesis. The analyses included monitoring the reactions, determining the yields and diastereoselectivities of the products, and characterizing the structures of the synthesized compounds using techniques like X-ray diffraction analysis for compound 29h. The research resulted in the synthesis of various methyl (5S)-5-alkyltetramate derivatives that are otherwise inaccessible by conventional methods based on α-amino acids.
10.1016/S0040-4039(01)00829-2
The research focuses on the development of a synthetic approach to enantiopure α-methoxy carboxyl derivatives using a chiral titanium enolate and dimethyl acetals. The main reactants involved are (S)-N-acetyl-4-isopropyl-1,3-thiazolidine-2-thione and various dimethyl acetals. The experiments utilized Lewis acids, such as BF3·OEt2 and SnCl4, to enhance the electrophilicity of the acetals and improve the stereoselectivity and yield of the process. The reactions were conducted at low temperatures (-78°C) and monitored using HPLC analysis to determine the diastereomeric ratios and overall yields. The adducts obtained were then transformed into a range of enantiopure α-unsubstituted α-methoxy carboxyl derivatives through the removal of the chiral thiazolidine-2-thione auxiliary, which was achieved using mild conditions and resulted in high yields. The analyses used to confirm the structures and absolute configurations of the adducts included spectroscopic and analytical data, as well as chemical correlation. The methodology described provides an efficient way to synthesize chiral building blocks useful in the total synthesis of natural products.
10.1055/s-0028-1087481
The study presents an improved method for the 1,4-alkynylation of acyclic enones using potassium organotrifluoroborates (K[F3BC≡CR]) in the presence of BF3·OEt2 as a Lewis acid promoter. The chemicals used in the study include aryl boronic acids, vinyltrifluoroborates, potassium organotrifluoroborates, and BF3·OEt2. These reagents serve as sp-hybridized nucleophiles and Lewis acid catalysts, respectively, to facilitate the rapid conjugate alkynylation reaction, which is suitable for the preparation of small compound libraries. The purpose of these chemicals is to increase the rate of the 1,4-addition reaction and to improve the yield of the desired alkynylation products, overcoming the limitations of previous methods that were slow and sensitive to hydrolysis.
10.1016/S0040-4039(01)93851-1
The study aimed to develop a new method for the synthesis of 1,3,5-triselenane from aldehydes and to generate selenoaldehyde via the fragmentation of 1,3,5-triselenane. The aim was to establish a convenient method for the generation of selenoaldehyde, a reactive intermediate containing a carbon-selenium double bond and of great importance in heteroatom chemistry. The researchers used chemicals such as (Me3Si)2Se (bis(trimethylsilyl)selenium) and Lewis acids such as BF3.OEt2 and SnCl4 in the reaction. The study concluded that 1,3,5-triselenane can be formed via the instantaneous generation of selenoaldehyde by treating aldehydes with (Me3Si)2Se in the presence of Lewis acids.
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