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Oxazoline Ring (oxazoline + ring)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

ChemInform Abstract: Oxazolinylferrocene Ligands for the Addition of Diethylzinc to Benzaldehyde: Effects of the Symmetry and the Substituent on the Oxazoline Ring of the Ligands on Asymmetric Catalysis.

CHEMINFORM, Issue 5 2001
Wanbin Zhang
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Novel Cyclic 1,2-Diacetals Derived from (2R,3R)-(+)-Tartaric Acid: Synthesis and Application as N,O Ligands for the Enantioselective Alkylation of Benzaldehyde by Diethylzinc

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2004
M. Teresa Barros
Abstract A chiral cyclic 1,2-diacetal derived from tartaric acid was used as the basic structural unit for novel ligands. Monooxazoline carbinols in which the degree of substitution of the alcohol and the nature of the stereocentre in the oxazoline ring were varied were synthesized in moderate to good yields. The influence of these structural factors on asymmetric induction was examined in the enantioselective addition of diethylzinc to benzaldehyde. Up to 60% ee was observed with a secondary or a tertiary alcohol as the metal-chelating group. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Homogeneous Hydrogenation of Tri- and Tetrasubstituted Olefins: Comparison of Iridium-Phospinooxazoline [Ir-PHOX] Complexes and Crabtree Catalysts with Hexafluorophosphate (PF6) and Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF) as Counterions

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2008
Bettina Wüstenberg
Abstract Four iridium complexes with achiral phosphino-oxazoline (PHOX) ligands were readily prepared in two steps starting from commercially available phenyloxazolines. The air-stable complexes with tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (BArF) as counterion showed high reactivity in the hydrogenation of a range of tri- and tetrasubstituted olefins. The best results were obtained with an iridium complex (11) derived from a dicyclohexylphosphino-oxazoline ligand bearing no additional substituents in the oxazoline ring. With several substrates, which gave only low conversion with the Crabtree catalyst, [Ir(Py)(PCy3)(COD)]PF6, full conversion was observed. The productivity of the Crabtree catalyst could be strongly increased by replacing the hexafluorophosphate anion with tetrakis[3,5-bis(trifluoromethyl)phenyl]borate. In one case, in the hydrogenation of a tetraalkyl-substituted CC bond, [Ir(Py)(PCy3)(COD)]BArF gave higher conversion than catalyst 11. However, with several other substrates complex 11 proved to be superior. [source]

Concise Total Synthesis of the Thiazolyl Peptide Antibiotic GE2270,A

CHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2008
Oscar Delgado Dr.
Abstract The potent antibiotic thiazolylpeptide GE2270,A was synthesized starting from N - tert -butyloxycarbonyl protected valine in a longest linear sequence of 20 steps and with an overall yield of 4.8,%. Key strategy was the assembly of the 2,3,6-trisubstituted pyridine core by consecutive cross-coupling reactions starting from 2,6-dibromo-3-iodopyridine. The complete Southern fragment was installed by Negishi cross-coupling of 3-zincated 2,6-dibromopyridine at the terminal 2-iodothiazole of a trithiazole (87,%). The substituent at C-6 representing the Northern part of the molecule was introduced in form of the truncated tert -butyl 2-bromothiazole-4-carboxylate after metalation to a zinc reagent by another Negishi cross-coupling (48,%). Decisive step of the whole sequence was the macrocyclization to a 29-membered macrolactam, which was conducted as an intramolecular Stille cross-coupling occurring at C-2 of the pyridine core and providing the desired product in 75,% yield. The required stannane was obtained by amide bond formation (87,%) between a complex dithiazole fragment representing the Eastern part of GE2270,A and a 3,6-disubstituted 2-bromopyridine. Final steps included attachment of a serine-proline amide dipeptide to the Northern part of the molecule (65,%), formation of the oxazoline ring and silyl ether deprotection (55,% overall). [source]