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Different Nucleophiles (different + nucleophile)
Selected AbstractsGold(III) Chloride-Catalyzed Diastereoselective Alkylation Reactions with Chiral Benzylic AcetatesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2008Philipp Rubenbauer Abstract Gold(III) chloride was shown to be an efficient catalyst for the diastereoselective CC bond formation of various chiral para -methoxybenzylic acetates and different nucleophiles. All electrophilic acetates carried next to the reacting center a stereogenic carbon center bound to a functional group (FG), a methyl substituent and a proton. Selectivities were good (dr>80/20) in favor of the anti -product for FG=COOMe, NO2, CN and in favor of the syn -product for FG=SO2Et, PO(OEt)2. The reactions proceed most likely via a free carbocation, in which a face differentation is facilitated by a preferred conformation. Several arene nucleophiles were shown to be compatible with the catalysis conditions providing the corresponding substitution products in high yields (13 examples, 62,98%). Moreover, other nucleophiles (allyltrimethylsilane, trimethylsilyl cyanide, 2,2-dimethyl-3-(trimethylsilyloxy)butane, p -toluenesulfonamide, and acetylacetone) reacted with a representative chiral electrophile in a high yielding and diastereoselective fashion. [source] Ethyl-3,4-diaroyl-2-cyanobutyrate: A Synthon for novel heterocyclesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2009Adivireddy Padmaja A new class of aminopyrazolones, aminoisoxazolones, aminopyrimidinones, and thioxopyrimidinones were synthesized from Michael adduct, ethyl-3,4-diaroyl-2-cyanobutyrate, on reaction with different nucleophiles, hydrazine hydrate, hydroxylamine hydrochloride, and urea derivatives. J. Heterocyclic Chem., (2009). [source] One-pot synthesis of [11C]ureas via triphenylphosphiniminesJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 4 2006Erica W. van Tilburg Abstract A series of 11C-labeled ureas was prepared using a rapid and efficient one-pot procedure. First, the intermediate [11C]phenylisocyanate was formed with phenyltriphenylphosphinimine and [11C]CO2. A range of amines was then reacted with the [11C]phenylisocyanate yielding the [11C]urea derivatives in short synthesis times. This easy-to-handle method circumvents disadvantages of known procedures and generates the possibility to prepare other kinds of 11C-labeled compounds using a variety of phenylphosphinimines in combination with different nucleophiles. The presented approach is an alternative to the use of established methods in 11C-labeling chemistry. Copyright © 2006 John Wiley & Sons, Ltd. [source] Palladium(II)-catalyzed catalytic aminocarbonylation and alkoxycarbonylation of terminal alkynes: regioselectivity controlled by the nucleophilesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 1 2010Rami Suleiman Abstract The aminocarbonylation and alkoxycarbonylation reactions of terminal alkynes took place smoothly and efficiently using a catalyst system Pd(OAc)2,dppb,p -TsOHCH3CNCO under relatively mild experimental conditions. The catalytic system was tested and optimized using two different nucleophiles: alcohols and amines. Phenylacetylene (1a) was considered as an alkyne along with diisobutylamine (2b1) and methanol (2c1) as nucleophiles. The results showed significant differences in the conversion of 1a and in the selectivity towards the gem or trans unsaturated esters or amides with these nucleophiles. The effects of the type of palladium catalysts, the type of ligands, the amount of dppb and the solvents were carefully studied. With diisobutylamine (2b1), excellent regioselectivity towards the 2-acrylamides (gem isomer, 3ab1) was almost always observed, while trans -,,,-unsaturated esters 4ac1 was the predominant product with methanol (2c1) as a nucleophile. This remarkable sensitivity in the selectivity of the reaction indicates two different possible mechanistic pathways for these carbonylation reactions. Copyright © 2009 John Wiley & Sons, Ltd. [source] From , - N-tert -butyloxycarbonyl N -carboxyanhydrides to , -aminoacid derivativesCHEMICAL BIOLOGY & DRUG DESIGN, Issue 6 2003J. Huck Abstract:,, - N-tert -butyloxycarbonyl- N -carboxyanhydrides are very reactive , -amino acid derivatives. They react cleanly and smoothly with different nucleophiles like aminoesters, enolates, N -methyl- d -glucamine, amidoximes to afford in good to excellent yields peptides, , -amino ketocompounds, , -aminosugars and functionalized disubstituted 1,2,4-oxadiazoles. [source] | ||||||||||