Orwik

A General and Special Catalyst for Suzuki–Miyaura Coupling Processes

Biaryl-Monophosphorliganden mit einem 2,3-Dihydrobenzo[d][1,3]oxaphosphol-Gerüst ergeben hoch effiziente palladiumkatalysierte Suzuki-Miyaura-Kreuzkupplungen mit verschiedenartigen Substraten. Der Ligand 1 eignet sich außerordentlich gut f... expand abstractür Kupplungen von sterisch stark gehinderten Arylboronsäuren. collapse abstract

ChemInform Abstract: Novel and Efficient Chiral Bisphosphorus Ligands for RhodiumCatalyzed Asymmetric Hydrogenation.

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&r... expand abstractdquo; option. The original article is trackable via the “References” option. collapse abstract

Copper catalyzed asymmetric propargylation of aldehydes.

The highly enantio- and regioselective copper catalyzed asymmetric propargylation of aldehydes with a propargyl borolane reagent is reported. The methodology demonstrated broad functional group tolerance and provided high enantioselectivities for ali... expand abstractphatic, vinyl, and aryl aldehydes. The utility of the TMS homopropargylic alcohols was demonstrated by the facile conversion to a chiral dihydropyranone. collapse abstract

ChemInform Abstract: Novel, Tunable, and Efficient Chiral Bisdihydrobenzooxaphosphole Ligands for Asymmetric Hydrogenation.

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&r... expand abstractdquo; option. The original article is trackable via the “References” option. collapse abstract

ChemInform Abstract: A Facile and Practical Synthesis of NAcetyl Enamides.

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&r... expand abstractdquo; option. The original article is trackable via the “References” option. collapse abstract

Novel and efficient chiral bisphosphorus ligands for rhodium-catalyzed asymmetric hydrogenation.

A series of structurally novel, operationally convenient, and efficient chiral 2-phosphino-2,3-dihydrobenzo[d][1,3]oxaphosphole ligands was developed. Applications of ligands 3a and 3b in rhodium-catalyzed asymmetric hydrogenation of alpha-(acylamino... expand abstract)acrylates and beta-(acylamino)acrylates provided excellent enantioselectivities (up to >99% ee) and reactivities (up to 10,000 TON). collapse abstract

Novel, tunable, and efficient chiral bisdihydrobenzooxaphosphole ligands for asymmetric hydrogenation.

A series of novel, efficient, air-stable, and tunable chiral bisdihydrobenzooxaphosphole ligands (BIBOPs) were developed for rhodium-catalyzed hydrogenations of various functionalized olefins such as alpha-arylenamides, alpha-(acylamino)acrylic acid ... expand abstractderivatives, beta-(acylamino)acrylates, and dimethyl itaconate with excellent enantioselectivities (up to 99% ee) and reactivities (up to 2000 TON). collapse abstract

A facile and practical synthesis of N-acetyl enamides.

A facile and practical method for the synthesis of N-acetyl alpha-arylenamides has been developed from corresponding ketoximes as the starting materials with ferrous acetate as the reducing reagent. This methodology offers mild reaction conditions, s... expand abstractimple purification procedures, and high yields for a variety of N-acetyl enamides. collapse abstract

Formation of 2-Trifluoromethylphenyl Grignard Reagent via Magnesium−Halogen Exchange: Process Safety Evaluation and Concentration Effect

The thermal stability profile for a solution of 2-trifluoromethylphenyl magnesium chloride at 1.5 M concentration in THF was determined using an Advanced Reactive System Screening Tool (ARSST). The solution generated by employing Knochel’s magn... expand abstractesium−halogen exchange protocol showed highly exothermic decomposition. The decomposition begins at a low-onset temperature accompanied by a rapid temperature and pressure rise. Analysis of the decomposition mixture revealed the destruction of trifluoromethyl group and formation of fluoride ion. This decomposition profile was substantially attenuated by reducing the concentration of the solution to 0.5−0.6 M. Thus, it is strongly recommended that selecting an appropriate concentration for the reagent based on calorimetric evaluation should be included with procedural and engineering controls when considering any strategy for safe scale-up of trifluoromethyl-substituted phenyl Grignard solutions. collapse abstract

ChemInform Abstract: Other Bisphosphine Ligands for Enantioselective Alkene Hydrogenation

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text&r... expand abstractdquo; option. The original article is trackable via the “References” option. collapse abstract

Chromatographic and spectroscopic studies on the chiral recognition of sulfated beta-cyclodextrin as chiral mobile phase additive enantiomeric separation of a chiral amine.

A fast enantiomeric separation of a chiral aromatic amine was achieved, using ultra high pressure liquid chromatography and highly sulfated beta-cyclodextrin (S-beta-CD) as a chiral additive in the mobile phase. The stationary phase consisted of a co... expand abstractre-shell support with a particle size of 2.7mum. Under these conditions the base-line separation was obtained within 2.5min. The influence of the concentration of the additive, along with the thermodynamics of the separation, was studied. Vibrational circular dichroism (VCD) spectroscopy was applied to assess the absolute configuration of the two enantiomeric analytes, as well as the interaction of these enantiomers with the S-beta-CD. The VCD results revealed that S-beta-CD undergoes a temperature-induced conformational change. Further, VCD experiments indicate that the interactions of the two enantiomers with the S-beta-CD occur through an inclusion of the aromatic part of the analyte, as well as through electrostatic interaction between the protonated amine and the sulfate groups located at the narrow part of the S-beta-CD. Molecular mechanics calculations performed according to the VCD results are consistent with experimental data, providing further evidence of these interactions. collapse abstract

Development of a Preparative-Scale Asymmetric Synthesis of (R)-p-Tolyl Methyl Sulfoxide for Use in a One-Pot Synthesis of a Drug Intermediate Containing a Trifluoromethyl-Substituted Alcohol Functionality

A one-pot process for the synthesis of (S)-1,1,1-trifluoro-4-(5-fluoro-2-methoxy-phenyl)-4-methyl-2-((R)-toluene-4-sulfinylmethyl)pentan-2-ol (3) is described, which was a key intermediate for the preparation of a class of novel glucocorticoid recept... expand abstractor ligands. The chemistry features the preparative-scale synthesis of (R)-p-tolyl methyl sulfoxide [(R)-pTMSO] from (2R,4S,5R)-4-methyl-5-phenyl-3-(tolene-4-sulfonyl)oxathiazolidine-2-oxide (5) and the synthesis of 3 from 5 without isolation of (R)-pTMSO during the process. collapse abstract

Total synthesis and structural elucidation of azaspiracid-1. Final assignment and total synthesis of the correct structure of azaspiracid-1.

The molecular structure of azaspiracid-1, a neurotoxin isolated from mussels, has been elucidated by total synthesis which also enriched its supplies. The degradatively derived fragments of this marine biotoxin, compounds 5 (EFGHI), 6 (FGHI), and 40 ... expand abstract(ABCD), were matched with synthetic materials, thus confirming their structural identities. Based on this detective work, a new structure of azaspiracid-1 (i.e., 1) was proposed and constructed by total synthesis. The final strategy for the total synthesis of azaspiracid-1 featured a dithiane anion (C(21)-C(27) fragment) reacting with a pentafluorophenol ester (C(1)-C(20) fragment) followed by a Stille-type union of an advanced allylic acetate substrate (C(1)-C(27) fragment) with a vinyl stannane as the main coupling processes to assemble the carbon skeleton of the molecule. In addition to the total synthesis of azaspiracid-1 (1), the syntheses of its C(1)-C(20) epimer (2) and of several truncated analogues for biological investigations are described. collapse abstract

Total synthesis and structural elucidation of azaspiracid-1. Synthesis-based analysis of originally proposed structures and indication of their non-identity to the natural product.

The key building blocks (6, 7, and 8) for the intended construction of the originally proposed structures of azaspiracid-1, a potent marine-derived neurotoxin, were coupled and the products elaborated to the targeted compounds (1a,b) and their C-20 e... expand abstractpimers (2 and 3). The assembly of the three intermediates was accomplished by a dithiane-based coupling reaction that united the C(1)-C(20) (7) and C(21)-C(27) (8) fragments, followed by a Stille-type coupling which allowed the incorporation of the C(28)-C(40) fragment (6) into the growing substrate. Neither of the final products (1a,b) matched the natural substance by TLC or (1)H NMR spectroscopic analysis, suggesting one or more errors in the originally proposed structure for this notorious biotoxin. collapse abstract

RhodiumCatalyzed Asymmetric Hydrogenation

For Abstract see ChemInform Abstract in Full Text.

A catalytic asymmetric three-component 1,4-additionaldol reaction: enantioselective synthesis of the spirocyclic system of vannusal A.

Cover Picture: Structural Revision and Total Synthesis of Azaspiracid1, Part 1: Intelligence Gathering and Tentative Proposal (Angew. Chem. Int. Ed. 332004)

The mussel toxin azaspiracid-1, which was isolated from Mytilus edulis, has baffled chemists for quite some time, as the originally proposed structure was incorrect. In their Communications on pages 4312 ff. and 4318 ff., Nicolaou and co-workers desc... expand abstractribe how they determined the structure and absolute configuration of the molecule through degradation studies and total synthesis. The synthesis should render this valuable, but scarce, substance available for much-needed biotoxin assays and biological investigations. collapse abstract

Structural revision and total synthesis of azaspiracid-1, part 1: intelligence gathering and tentative proposal.

Structural revision and total synthesis of azaspiracid-1, part 2: definition of the ABCD domain and total synthesis.

Synthesis of a New Class of Conformationally Rigid Phosphino-oxazolines:  Highly Enantioselective Ligands for Ir-Catalyzed Asymmetric Hydrogenation

A new class of conformationally rigid phosphino-oxazoline ligands were synthesized from readily available enantiopure phenyl glycinol. Ir complexes with these ligands are air-stable and highly enantioselective catalysts for asymmetric hydrogenation o... expand abstractf aryl alkenes and α,β-unsaturated esters in up to 99% ee. collapse abstract

Synthesis of a new class of conformationally rigid phosphino-oxazolines: highly enantioselective ligands for Ir-catalyzed asymmetric hydrogenation.

[reaction: see text] A new class of conformationally rigid phosphino-oxazoline ligands were synthesized from readily available enantiopure phenyl glycinol. Ir complexes with these ligands are air-stable and highly enantioselective catalysts for asymm... expand abstractetric hydrogenation of aryl alkenes and alpha,beta-unsaturated esters in up to 99% ee. collapse abstract

Enantioselective Hydrogenation of Tetrasubstituted Olefins of Cyclic β(Acylamino)acrylates.

For Abstract see ChemInform Abstract in Full Text.

A Bisphosphepine Ligand with Stereogenic Phosphorus Centers for the Practical Synthesis of βArylβamino Acids by Asymmetric Hydrogenation.

For Abstract see ChemInform Abstract in Full Text.

Enantioselective hydrogenation of tetrasubstituted olefins of cyclic beta-(acylamino)acrylates.

Hydrogenation of a series of cyclic beta-(acylamino)acrylates with tetrasubstituted olefins has been accomplished successfully with the use of Ru catalysts with chiral biaryl ligands such as C3-TunaPhos, and up to over 99% ee's have been achieved. Th... expand abstractis methodology provides an efficient catalytic method for the synthesis of both cis and trans chiral cyclic beta-amino acid derivatives. collapse abstract

A bisphosphepine ligand with stereogenic phosphorus centers for the practical synthesis of beta-aryl-beta-amino acids by asymmetric hydrogenation.