Showing papers in "Organic Letters in 2001"

TL;DR: Analysis of the basic π-aromatic (benzene) and antiaromatic systems by dissected nucleus-independent chemical shifts (NICS) shows the contrasting diatropics and paratropic effects, but also reveals subtleties and unexpected details.

TL;DR: This work has examined a simple but powerful strategy to convert air-sensitive trialkylphosphines into air-stable phosphonium salts via protonation on phosphorus, which serve as direct replacements for the corresponding phosphines in a diverse set of applications.

TL;DR: Mild synthetic protocols for the formation of aryl-carbon, aryL-nitrogen, and aryal-oxygen bonds based on soluble, well-defined copper(I) catalysts do not require the use of palladium and/or expensive ligands.

TL;DR: This novel reaction provides gamma-nitro ketones in modest enantioselectivity yet excellent yields as well as proline-catalyzed Michael addition of unmodified ketones to nitro olefins.

TL;DR: Direct catalytic enantio- and diastereoselective Michael addition reactions of unmodified aldehydes to nitro olefins using (S)-2-(morpholinomethyl)pyrrolidine as a catalyst are described.

TL;DR: The first enantioselective ruthenium olefin metathesis catalysts have been prepared, and high enantiomeric excesses are observed in the desymmetrization of achiral trienes and a model consistent with the stereochemical outcome of the reactions is described.

TL;DR: This communication extends the methodology of proline-catalyzed direct asymmetric aldol reactions to include alpha-unsubstituted aldehydes as acceptors and develops a concise new synthesis of (S)-ipsenol.

TL;DR: The ortho position of the aromatic ring of imino group substituted aromatic compounds is directly arylated and alkenylated with organic halides in the presence of a catalytic amount of a ruthenium(II)-phosphine complex.

TL;DR: Nucleus-independent chemical shifts (NICS) indicate that the more reactive inner rings actually are more reactive than the less reactive outer rings and even more aromatic than benzene itself.

TL;DR: Lipase-catalyzed transesterifications in ionic liquids proceeded with markedly enhanced enantioselectivity, and it was observed that lipases were up to 25 times more enantiosing than in conventional organic solvents.

TL;DR: In this article, a mild and efficient cyclization method can be applied to alkyl- and alkenyl-substituted allenes at room temperature, furnishing tri- and tetrasubstitized dihydrofurans in good to excellent chemical yields and with complete axis to center chirality transfer.

TL;DR: Fused 5-heterotetrazole ring systems are synthesized in high yield via intramolecular [2 + 3] cycloadditions of organic azides and heteroatom-substituted nitriles through competent dipolarophiles for this reaction.

TL;DR: In this paper, the authors demonstrate that Pd/C without added ligands catalyzes the Suzuki cross-coupling reaction with aryl chlorides and demonstrate the importance of selectivity control following C−Cl bond activation.

TL;DR: NiCl(2)(PCy(3))(2) associated with PCy( 3) promotes the selective cross-coupling of aryltosylates with arylboronic acids under relatively mild reaction conditions, and a variety of functional groups are tolerated in both arenes.

TL;DR: A reversal in regioselectivity is observed for the arylation of benzoic hydrazide with ortho-substituted aryl iodides, providing the N'-arylated products B.

TL;DR: A general catalytic coupling of arylboronic acids and amines is reported, realized through the use of catalytic copper(II) acetate, 2,6-lutidine as base, and myristic acid as an additive.

TL;DR: A new phosphine-imidazolium salt that has proven to be highly efficient in the Heck coupling reactions of aryl bromides with n-butyl acrylate in the presence of Cs(2)CO(3) as base.

TL;DR: A new, convenient procedure for the addition reaction of trimethylsilylacetylene to imines is described, and it is suggested that the reaction may be conducted in the absence of solvent.

TL;DR: Diphenylphosphinomethanethiol thioesters are shown to give high isolated yields for this transformation of peptides, providing precedent for a powerful and versatile new method for the total synthesis of proteins.

TL;DR: The CuI-catalyzed coupling reaction of aryl halides with β-amino acids or β- amino esters is completed at 100 °C in 48 h, which indicates that the structure of the β-Amino acid has an accelerating effect for the Ullmann-type aryL amination reaction.

TL;DR: The full sequence of the 6.7 kb eDNA violACEin gene cluster and the characterization of violacein and deoxyviolacein from an eDNA clone are reported here.

TL;DR: A novel blue shift along with an intensity enhancement of the pyrene excimer emission is observed for 1 in the presence of Cu(2+) and a new signal transduction mode of pyrene probes results from the formation of a static pyreneexcimer that has very different characteristics from its dynamic counterpart.

TL;DR: Flexible, convergent access to 2,3-disubstituted benzo[b]thiophenes has been developed and this method has been applied to the synthesis of some novel tubulin binding agents.

TL;DR: Treatment of the crude reaction products with triphenylphosphine oxide or dimethyl sulfoxide, followed by filtration through silica gel, was found to be a practical and effective method to remove colored ruthenium byproducts.

TL;DR: Under the optimal conditions employing a 1,5-diaza-cis-decalin copper(I) iodide complex with oxygen as the oxidant, rapid and highly selective couplings could be achieved.

TL;DR: Several other late transition metals with d(8) configuration allow this conversion, providing evidence for Au(III) being a catalytically active species, and gold was still the most active catalyst and gives the cleanest conversion.

TL;DR: A new chromogenic azophenol-thiourea based anion sensor, 2, has been developed, which allows for the selective colorimetric detection of F, H2PO4-, and AcO.

TL;DR: Fmoc-Se-p-methoxybenzylselenocysteine was prepared and used for solid-phase synthesis of peptides with an N-terminal unprotected selenocysteines and provided a 17-mer that corresponds to the C-terminus of ribonucleotide reductase with selenocytesteine in place of cysteine.

TL;DR: Pure α-azido acids were prepared using an efficient diazo transfer method followed by buffered workup and these building blocks were used to prepare small peptides on Wang resin by two approaches.

TL;DR: In this article, the authors showed that α-amino alcohols can be rapidly oxidized without no overoxidation to carboxylic acids, and secondary carbinols are slowly oxidized so that the reaction is highly chemoselective.