Activated Carbonyl Compounds Research Articles

Reactions of Some Active Carbonyl Compounds with 4‐Aryl‐1,6‐diamino‐2‐oxo‐1,2‐dihydropyridine‐3,5‐dicarbonitrile Derivatives.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Silica Sulfuric Acid-Catalyzed Reaction of 4-Hydroxy Proline with 11H-Indeno[1,2-b]quinoxalin-11-one and Isatin Derivatives: A Novel Synthesis of New Pyrrole Compounds

Facile reaction involving 4-hydroxy proline and activated carbonyl compounds such as 11H-indeno[l,2-b]quinoxalin-l 1-one and isatin derivatives catalyzed by silica sulfuric acid under microwave irradiation yielding some novel 11-(1H-pyrrol-l-yl)-l H-indeno[l,2-b]quinoxaline and 3-(1H-pyrrol-1-yl)indolin-2-one derivatives are described.

Activation of Carbonyl Compounds by Double Hydrogen Bonding: An Emerging Tool in Asymmetric Catalysis.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Activation of carbonyl compounds by double hydrogen bonding: an emerging tool in asymmetric catalysis.

Activation of carbonyl compounds by double hydrogen bonding: an emerging tool in asymmetric catalysis.

Direct catalytic asymmetric aldol reactions of pyruvates: scope and mechanism.

The direct aldol reaction of 2-ketoesters catalyzed by chiral bisoxazoline copper(II) complexes has been investigated. First the direct homo-aldol reaction of ethyl pyruvate is reported which proceeds to give diethyl 2-hydroxy-2-methyl-4-oxoglutarate. This was isolated as the more stable optically active isotetronic acid in good yield and enantiomeric excess in the absence of bases such as amines. Detailed investigations of the use of different chiral Lewis acids as the catalyst, amines, ratios of chiral bisoxazoline copper(II) salts:amine, and solvents gave up to 96% ee of the isotetronic acid. Then the reaction was extended to a cross-aldol reaction of various 2-ketoesters with activated carbonyl compounds to give the cross-aldol adduct with excellent enantiomeric excess. Furthermore, the synthesis of the isotetronic acids was investigated from these cross-aldol adducts giving important information about the formation of the stereogenic centers during the aldol reaction. Based on the absolute configuration of the homo-aldol adduct the mechanism for the aldol reaction is discussed.

Asymmetric Friedel-CraftsReactions: Catalytic Enantioselective Addition of Aromatic and HeteroaromaticC-H Bonds to Activated Alkenes, Carbonyl Compounds, andImines

The development and scope of catalytic enantioselective addition of aromatic and heteroaromatic C-H bonds to α,β-unsaturated alkenes, carbonyl compounds, and imines are presented. α,β-Unsaturated alkenes, 4-substituted 2-oxo-3-butenoate esters and alkylidene malonates react with indoles, furans and electron-rich aromatic compounds in the presence of chiral bisoxazoline-copper(II) complexes to give the Friedel-Crafts alkylation adduct in moderate to high yields and with up to >99.5% ee. Chiral bisoxazoline-copper(II) complexes can also catalyze the enantioselective addition of especially electron-rich aromatic compounds to activated carbonyl compounds such as glyoxylates and trifluoropyruvate to give e.g. optically active aromatic mandelic acid esters in good yields and enantioselectivities. Electron-rich aromatic compounds and heteroaromatic compounds react in an enantioselective fashion with activated N-protected α-imino esters to give optically active aromatic and heteroaromatic α-amino acid derivatives using chiral BINAP­-copper(I) complexes as the catalyst.

Direct catalytic asymmetric aldol reactions of aldehydes.

The development of a direct catalytic enantioselective aldol reaction of aldehydes with activated carbonyl compounds catalyzed by chiral amines is presented and the potential demonstrated by the synthesis of optically active beta-hydroxycarboxylic acid derivatives.

Progress in Karl Fischer coulometry using diaphragm-free cells.

Different designs of a semiopen, drainable cathode compartment of a medium-sized coulometric Karl Fischer (KF) cell for the determination of water in the range 0.1-500 microg were evaluated. The main criterion for the design was to keep the resistance between the anolyte and catholyte low enough to permit the generation of currents larger than 20 mA (for an output voltage of 28 V). It was found that a good compromise between the size of this current and a minimal influence from diffusing/migrating oxidizable reduction products from the catholyte was achieved by means of an interface having a channel length and diameter of 8 and 2.1 mm, respectively (catholyte volume, approximately 1 mL). To show the general applicability of the concept, the following different types of coulometric reagents suitable for nonpolar and polar samples, as well as for samples containing active carbonyl compounds, were investigated: Hydranal Coulomat A, AD, AK, AG-H (modified with chloroform, Merck), and two homemade methanolic reagents modified with 40% (v/v) chloroform and 50% (v/v) formamide, respectively. Except for Hydranal Coulomat A, the mean value of five consecutive titrations of 50 microg water did not deviate by more than 0.2% from the expected value for all reagents. Draining after every titration was sufficient to obtain accurate results, even for Coulomat A which, when used in the commercial diaphragm-free system of Metrohm, gave values which were about 10% too high. As compared to earlier reported results for diaphragm-free coulometry, the descibed modified cell represents a significant improvement, mainly because of the high accuracy achieved for all types of reagents.

Model of Reactant–Modifier Interaction in Enantioselective Hydrogenation of Ethyl Pyruvate on Platinum–Cinchona Catalysts: Extension to Synthetic Chiral Modifiers

The previously proposed model for reactant–modifier interaction in the enantioselective hydrogenation of activated carbonyl compounds over platinum chirally modified by cinchona alkaloids has been extended to platinum modified by synthetic pyrrolidinyl–naphthyl–ethanol modifiers. As in the case of cinchonidine, the most used modifier, the model predicts enantiomeric excess in nearly quantitative agreement with experiment. Excellent agreement is achieved despite the fact that structural assumptions had to be made and the platinum surface was not explicitly taken into account. The one-to-one interaction between modifier and reactant was calculated at the ab initio level. A comparison of the results for different modifiers leads to the conclusion that steric repulsion caused by the anchoring group plays an important role in the enantiodifferentiating interaction. The favoured formation of the (R)-product is traced to the fact that the pro-(S) complex leading to the (S)-product upon hydrogenation is more destabilised due to repulsive interaction than the pro-(R) complex. The model calculations are a useful tool for designing effective modifiers and for gaining insight into the mechanism of enantiodifferentiation.

Catalytic Asymmetric Hetero-Diels-Alder Reactions of Carbonyl Compounds and Imines.

Asymmetric catalysis is a challenge for chemists: How can we design catalysts to achieve the goal of forming optically active compounds? This review provides the reader with an overview of the development of catalytic asymmetric hetero-Diels-Alder reactions of carbonyl compounds and imines. Since its discovery, the Diels-Alder reaction has undergone intensive development and is of fundamental importance for synthetic, physical, and theoretical chemists. The Diels-Alder reaction has been through different stages of development, and at the beginning of the 21st century catalytic Diels-Alder reactions are one of the main areas of focus. The preparation of numerous compounds of importance for our society is based on cycloaddition reactions to carbonyl compounds and imines. There are several parallels between the reactions of carbonyl compounds and those of imines, which, however, begin to vanish on entering the field of catalytic reactions. Why? From a mechanistic point of view some similarities can be drawn, but the synthetic development of catalytic enantioselective hetero-Diels-Alder reactions of imines are several years behind those of the carbonyl compounds. For hetero-Diels-Alder reactions of carbonyl compounds there a number of different chiral catalysts, and great progress has been achieved in developing enantioselective reactions for unactivated and activated carbonyl compounds. In contrast the development of catalytic enantioselective hetero-Diels-Alder reactions of imines is in its infancy and only few catalytic reactions have been published. This review will focus on the most important developments, and discuss the synthetic and mechanistic aspects of enantioselective hetero-Diels-Alder reactions of carbonyl compounds catalyzed by chiral Lewis acids. For the hetero-Diels-Alder reactions of imines, the diastereoselective reactions of optically substrates catalyzed by Lewis acids will be presented first, followed by the catalytic enantioselective reactions.

Stereoselective reductions with macrocyclic NADH models

Macrocyclic NADH models with two ( C 2 symmetry) or four ( D 2 symmetry) nicotinamide units comprised in a ring have been prepared and found to reduce activated carbonyl compounds in good yields and high enantiomeric excess. The roles of magnesium ions as a cocatalyst and the temperature have also been investigated. The smaller, C 2-symmetric macrocycle gave 96% ee upon reduction of ethyl benzoylformate whereas the best result with the larger D 2-symmetric model was 81% ee for the reduction of methyl benzoylformate.

ChemInform Abstract: Development of a Chiral Propionaldehyde Homoenolate Equivalent Which Reacts with Imines with Excellent Stereoselectivity: Efficient and Practical Synthesis of Optically Active γ‐Amino Carbonyl Compounds.

AbstractChemInform 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.

A NEW SYNTHESIS OF α-AMINO ACID DERIVATIVES BY REACTION OF N-ACYL-α-TRIPHENYLPHOSPHOSPHONIO-GLYCINATES WITH CARBON NUCLEOPHILES

Recently described1, easily accessible N-acyl-α-triphenylphosphonioglycinates react smoothly with activated carbonyl compounds or enamines in the presence of a base (DBU or Et3N) yielding the corresponding α-functionalized glycine derivatives.

Asymmetric addition of chiral triquinphosphoranes on activated carbonyl compounds

Chiral triquinphosphoranes react with trifluoroacetophenone, ketopantolactone and aromatic aldehydes affording pairs of hydroxyphosphoranes diastereomers with a diastereoselectivity up to 90% depending on the nature of the electrophile. In the case of ketopantolactone, hydroxyphosphorane diastereomers are quantitatively converted to alkoxyphosphoranes with a decreasing of diastereomeric excesses. The major alkoxyphosphorane diastereomer exhibits a close SP structure determined by x-ray diffraction analysis.

ChemInform Abstract: The Aza‐Ene Reaction of Heterocyclic Ketene Aminals with Activated Carbonyl Compounds: A Novel and Efficient Synthesis of γ‐Lactam‐Fused Diazaheterocycles.

AbstractChemInform 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.

ChemInform Abstract: Vinylalumination of Activated Carbonyl Compounds.

AbstractChemInform 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.

The aza-ene reaction of heterocyclic ketene aminals with activated carbonyl compounds: a novel and efficient synthesis of γ-lactam-fused diazaheterocycles

Reactions of heterocyclic ketene aminals with activated carbonyl compounds are strongly influenced by the structure of the heterocycle moiety. Six-membered heterocyclic ketene aminals with or without an N-methyl group such as 3 and 4 underwent efficient addition and consecutive cyclocondensation reactions with diethyl oxomalonate 9 to produce γ-lactam-fused pyrimidine derivatives 10 and 11 in moderate to excellent yield. For the five-membered enediamines, however, those compounds without any N-substituent such as 6 underwent the same reaction slowly and no reaction at all was observed with N-methyl and N,N′-dimethyl-substituted analogs 7 and 8. Heterocyclic ketene aminals 3 also reacted with glyoxylic acid esters 17 to afford 8-aroyl-7-hydroxy-6-oxo-1,2,3,4,6,7-hexahydropyrrolo[1,2-a]pyrimidines 18 in good yield. No asymmetric induction was found, however, when (1R,2S,5R)-(–)-menthyl glyoxylate 17b was employed as a chiral substrate. An aza-ene reaction mechanism involving heterocyclic ketene aminals as the aza-ene component (H–N–CC) has been proposed. The effects of intramolecular hydrogen bonding and heterocyclic ring size on the reactivity are also discussed.

Vinylalumination of activated carbonyl compounds

[α-(Ethoxycarbonyl)vinyl]diisobutylaluminum and its β-methyl and -phenyl analogs react with activated ketones, such as α-keto esters, α-acyl cyanides, and α-acetylenic ketones to provide the corresponding α-hydroxyalkenylated products in high yields.

Mapping of a Novel Human Carbonyl Reductase, CBR3, and Ribosomal Pseudogenes to Human Chromosome 21q22.2

To find the genes contributing to Down syndrome, we constructed a 4-Mb sequence-ready map spanning chromosome 21q22.2 with megabase-sized cosmid/P1-derived artificial chromosome (PAC) contigs. The restriction map with rare cutting enzymes, followed by sequencing from the clustering sites, has defined CpG islands and revealed the genes associated with CpG islands (Accession No. D85771). Of these, two human carbonyl reductases (CBR; EC1.1.1.184) were found in a PAC 25P16 clone. CBR catalyzes the reduction of a large number of biologically and pharmacologically active carbonyl compounds to their corresponding alcohols and has been mapped in 21q22.1. To confirm these results, we sequenced the PAC clone in shotgun strategies and identified a novel carbonyl reductase, designated CBR3, 62 kb downstream from the original CBR. In addition, three ribosomal pseudogenes, L23a, S9, and L3, and some cDNAs with ESTs were mapped in the sequence. In conclusion, the sequence analysis for CpG islands predicted from the megabase-sized contigs will reveal and identify the genes involved in Down syndrome.

ChemInform Abstract: Synthesis of Highly Functionalized γ‐Butyrolactones from Activated Carbonyl Compounds and Dimethyl Acetylenedicarboxylate.

AbstractChemInform 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.