- Pyridyl-directed Cp?Rh(III)-catalyzed B(3)-H acyloxylation of o-carborane
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An efficient pyridyl-directed Rh(III)-catalyzed o-carborane B(3)-H acyloxylation is reported. The B(3)-H bond is the most electron-deficient vertex on o-carborane whose functionalization is challenging. The combination of Cu(OH)2 and diverse carboxylic acids provides low cost and abundant acyloxyl sources which could lead to moderate to excellent yields.
- Li, Chun-Xiao,Zhang, Hao-Yun,Wong, Tsz-Yung,Cao, Hou-Ji,Yan, Hong,Lu, Chang-Sheng
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- Deaminative chlorination of aminoheterocycles
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Selective modification of heteroatom-containing aromatic structures is in high demand as it permits rapid evaluation of molecular complexity in advanced intermediates. Inspired by the selectivity of deaminases in nature, herein we present a simple methodology that enables the NH2 groups in aminoheterocycles to be conceived as masked modification handles. With the aid of a simple pyrylium reagent and a cheap chloride source, C(sp2)?NH2 can be converted into C(sp2)?Cl bonds. The method is characterized by its wide functional group tolerance and substrate scope, allowing the modification of >20 different classes of heteroaromatic motifs (five- and six-membered heterocycles), bearing numerous sensitive motifs. The facile conversion of NH2 into Cl in a late-stage fashion enables practitioners to apply Sandmeyer- and Vilsmeier-type transforms without the burden of explosive and unsafe diazonium salts, stoichiometric transition metals or highly oxidizing and unselective chlorinating agents. [Figure not available: see fulltext.]
- Ghiazza, Clément,Faber, Teresa,Gómez-Palomino, Alejandro,Cornella, Josep
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- Basic techniques of working on a solid phase: From ABC of the peptide synthesis to libraries of non-natural amino acids
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Libraries of hardly available amino acids bearing a heteroaromatic ring (2-pyrimidyl, substituted 2-pyridyl or 2-thiazolyl) at the amino group were prepared using solid-phase synthesis on various resins. The synthesized compounds are structurally similar to some known antidiabetic drugs. The paper combines features of a review (elementary introduction to the solid-phase synthesis methodology and technique for beginners and selected methods from peptide chemistry) and step-by-step experimental protocols (tested by the authors) useful as a methodic tool. The presented protocols (immobilization and modification of amino acids, placing and removal of common protective groups) require no sophisticated equipment and may be useful as pictorial introductory tasks for students education. Pleiades Publishing, Ltd., 2010.
- Babaev,Ermolat'ev
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experimental part
p. 2572 - 2589
(2011/04/15)
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- Facile preparation of aromatic fluorides by deaminative fluorination of aminoarenes using hydrogen fluoride combined with bases
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One-pot deaminative fluorination of aminoarenes including heteroaromatics, namely, diazotization of aminoarenes followed by in situ fluoro-dediazoniation of the corresponding diazonium ions, was successfully accomplished to produce fluoroarenes in high yields by using hydrogen fluoride combined with base solutions. The diazotization stage has been found to play the most important part in yielding fluoroarenes effectively. It was greatly influenced by the composition of the HF solution and enhanced by employing appropriate amounts of bases such as pyridine under carefully controlled conditions. The fluoro-dediazoniation stage was effectively accelerated photochemically to afford fluoroarenes having polar substituents such as hydroxyl, nitro and so on in high yields.
- Yoneda,Fukuhara
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- Halogen-Exchange Fluorination of Aromatic Halides with HF or HF-Base
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Heteroatomic halides such as 2-chloropyrimidines and 2-chloropyridines, and 2,4-dinitrochlorobenzene underwent halogen-exchange fluorination with the treatment of HF or HF-base solutions to afford the corresponding fluorides in good yields.
- Fukuhara, Tsuyoshi,Yoneda, Norihiko
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p. 509 - 512
(2007/10/02)
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