A new method for the preparation of tertiary butyl ethers and esters
TL;DR: T-butyl 2,2,2-trichloroacetimidate is an efficient reagent for the preparation of t- butyl ethers and esters in the presence of a catalytic amount of boron trifluoride etherate.
About: This article is published in Tetrahedron Letters.The article was published on 1988-01-01. It has received 152 citations till now. The article focuses on the topics: Trichloroacetonitrile & Boron trifluoride.
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230 citations
TL;DR: The wide synthetic potential of levulinic acid, particularly as a key compound in the synthesis of various heterocyclic systems, saturated and unsaturated ketones and diketones, difficultly accessible acids and other compounds is demonstrated in this article.
Abstract: Data concerning the methods of synthesis, chemical transformations and application of levulinic acid are analysed and generalised. The wide synthetic potential of levulinic acid, particularly as a key compound in the synthesis of various heterocyclic systems, saturated and unsaturated ketones and diketones, difficultly accessible acids and other compounds is demonstrated. The accessibility of levulinic acid from hexose-containing wood-processing and agricultural wastes is noted. The bibliography includes 260 references.
140 citations
TL;DR: Preliminary cell uptake and inhibition studies using the 9L tumor cells and SF188(Bcl-xL) tumor cells provided strong evidence for their potential application in conjunction with positron emission tomography (PET) for in vivo imaging of tumors, which use glutamine as an alternative energy source.
Abstract: A versatile synthetic route to prepare all four stereoisomeric 4-fluoro-glutamines was developed by exploiting a Passerini three-component reaction. The skeleton of 4-substituted glutamine derivatives was efficiently constructed. Subsequent four-step reactions, highlighted by a “neutralized” TASF fluorination, provided the desired products with high yields and excellent optical purity. The optically pure fluorine-18 labeled 4-fluoroglutamines were also successfully prepared using either a 18-crown-6/KHCO3 or K[222]/K2CO3 catalysis system. Preliminary cell uptake and inhibition studies using the 9L tumor cells and SF188Bcl-xL tumor cells (a glutamine addicted tumor derived from glioblastoma) provided strong evidence for their potential application in conjunction with positron emission tomography (PET) for in vivo imaging of tumors, which use glutamine as an alternative energy source.
138 citations
TL;DR: X-ray structure analysis and ab initio calculations have been used to develop a model for rationalizing the stereoselectivities in these reactions with chiral hypervalent iodine reagents, and high enantiomeric excess in the reaction correlates with the relative population of a conformation in which a methyl group on the asymmetric carbon atom is in the axial position.
126 citations
TL;DR: In this article, the nucleophilic ring opening of optically active N-sulphonyl aziridine-2-carboxylate esters with organometallic reagents has been investigated as a method of preparation of amino acids.
119 citations
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TL;DR: Emphasis is placed on glycoside and saccharide formation by 1-O-alkylation, on the trichloroacetimidate method, and on activation through the formation of glycosylsulfonium salts and Glycosyl fluorides.
Abstract: Glycoproteins, glycolipids, and glycophospholipids (glycoconjugates) are components of membranes. The oligosaccharide residue is responsible for intercellular recognition and interaction; it acts as a receptor for proteins, hormones, and viruses and governs immune reactions. These significant activities have stimulated interest in oligosaccharides and glycoconjugates. With their help it should be possible to clarify the molecular basis of these phenomena and to derive new principles of physiological activity. Major advances in the synthesis of oligosaccharides have been made by the use of the Koenigs-Knorr method, in which glycosyl halides in the presence of heavy-metal salts are employed to transfer the glycosyl group to nucleophiles. The disadvantages of this procedure have led to an intensive search for new methods. Such methods will be discussed in this article. Emphasis is placed on glycoside and saccharide formation by 1-O-alkylation, on the trichloroacetimidate method, and on activation through the formation of glycosylsulfonium salts and glycosyl fluorides.
1,185 citations
TL;DR: In this article, trichloracetonitril lagert leicht Alkohole unter Bildung von Trichloracetimidsaureestern an: die Reaktion wird durch Alkali (Alkoholat, Salze der Alkoxysauren, Carbonat) katalysiert.
Abstract: Trichloracetonitril lagert leicht Alkohole unter Bildung von Trichloracetimidsaureestern an: die Reaktion wird durch Alkali (Alkoholat, Salze der Alkoxysauren, Carbonat) katalysiert. Die leichte Anlagerung der Alkohole kann mit dem induktiven Effekt der Cl-Atome erklart werden.
68 citations
TL;DR: O-Alkyl-N.N′-dicyclohexyl-isoharnstoffe reagieren mit carbonsauren zu Carbonsaureestern.
Abstract: O-Alkyl-N.N′-dicyclohexyl-isoharnstoffe reagieren mit Carbonsauren zu Carbonsaureestern. Bei Phenolcarbonsauren kann neben der Veresterung auch eine Alkylierung der phenolischen OH-Gruppe eintreten. Ungeschutzte Alkohol- und Aminogruppen storen den Reaktionsablauf nicht.
53 citations
TL;DR: In this paper, the durch Bortrifluorid katalysierte Umlagerung von Alkyl-trichloracetimidaten (I, R = CCl3, R′ = Alkyls, R″ = H) zu N-substituierten Saureamiden verlauft uber einen ionischen Mechanismus.
Abstract: Die durch Bortrifluorid katalysierte Umlagerung von Alkyl-trichloracetimidaten (I, R = CCl3, R′ = Alkyl, R″ = H) zu N-substituierten Saureamiden verlauft uber einen ionischen Mechanismus. Bei Trichloracetimidaten sekundarer oder tertiarer Alkohole wird teilweise oder vollstandige Eliminierung beobachtet. Methylallyl-trichloracetimidate werden teilweise isomerisiert, das Isomeren-verhaltnis erlaubt Ruckschlusse auf den Reaktionsmechanismus; in Gegenwart von Benzol entstehen Allylbenzole.
37 citations
TL;DR: In this paper, N-protected aminoacids by isopropenyl chloroformate leads to esters of primary, secondary and tertiary alcohols with 4-dimethylamino-pyridine as catalyst.
33 citations