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Carbonyl Function (carbonyl + function)
Selected AbstractsSilver versus Gold Catalysis in Tandem Reactions of Carbonyl Functions onto Alkynes: A Versatile Access to Furoquinoline and Pyranoquinoline CoresCHEMISTRY - A EUROPEAN JOURNAL, Issue 19 2007Thomas Godet Abstract An efficient and versatile tandem process of acetalization and cycloisomerization reactions has been developed for the reactions of 1-alkynyl-2-carbonylquinoline substrates. The reaction occurs thanks to AuI and AgI catalysis. Silver(I) catalysis has been extensively studied (11 different silver species) on a broad range of quinoline derivatives (variation of alkyne substituent, of carbonyl function and of nucleophiles), leading to a variety of furoquinoline and pyranoquinoline moieties. An insight is given for the presumed mechanism along with DFT-B3,LYP/6,31G** calculations to address the 6- endo and 5- exo regioselectivities observed. [source] Unexpected Tethering in the Synthesis of Methyl-Substituted Acetyl-1-oxaspiro[4.5]decanes: Novel Woody,Ambery Odorants with Improved Bioavailability,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2008Philip Kraft Abstract To study the olfactory properties of spirocyclic analogs of Iso Gamma (3) with improved water solubility and bioavailability, it was envisaged to spiroannulate 1-acetyl-1,2-dimethylcyclohexanone at the 4-position with a 3,3-dimethyltetrahydrofuran-2-yl moiety that would mimic the polarity of the double bond by its ether function. 3,3-Dimethyl-4-methylenehex-5-en-1-ol (9) was prepared by copper(I)-mediated 1,4-conjugate addition of the Grignard reagent of chloroprene (7) to 3-methylbut-2-enal with subsequent LAH reduction. However, the Diels,Alder reaction of diene 9 with (E)-3-methylpent-3-en-2-one in the presence of Me2AlCl unexpectedly provided exclusively the undesired meta adduct 10, as was discovered after cyclization to 11 with MeSO3H. The wrong selectivity was due to a tethering effect of the Lewis acid, and this could be evaded by changing the carbonyl function of the dienophile to a hydroxy group. Thereby the (5,R*,7,S*,8,S*)-configured 1-(4,,4,,7,,8,-tetramethyl-1,-oxaspiro[4.5]decan-7,/8,-yl)ethan-1-ones 11 and 14, as well as the like -configured 1-(4,,4,,7,-trimethyl-1,-oxaspiro[4.5]decan-7,/8,-yl)ethan-1-ones 16 and 19, were prepared selectively and studied for their odor characters, threshold values, and octanol/water partition coefficients. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Pyrrolidino DNA with Bases Corresponding to the 2-Oxo Deletion Mutants of Thymine and Cytosine: Synthesis and Triplex-Forming PropertiesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2007Alain Mayer Abstract The dual recognition properties of pyrrolidino DNA species as parallel triplex-forming oligonucleotides were previously found to be strongly dependent upon the nature of the pyrimidine bases. In the structure,activity study presented here we were able to exclude this differential binding being due to their 2-oxo function. We had previously reported on the incorporation of pyrrolidino C -nucleosides into triplex-forming 2,-deoxyoligonucleotides (TFOs). The basic nitrogen atom that replaces the 4,-oxygen atom of the 2,-deoxysugar in such modified units introduces a positive charge in the third strand, and this is able to produce favourable electrostatic interaction with the negatively charged DNA target duplex. A first series of pyrrolidino pseudonucleosides with the bases isocytosine and uracil proved successful for GC base-pair recognition, but was unsuccessful for AT base-pair recognition within the parallel triplex binding motif. Here we report on the synthesis of the two novel 2,-deoxypyrrolidino nucleosides carrying the bases pyridin-2-one and 2-aminopyridine, their phosphoramidite building blocks and theirincorporation into TFOs. Pyrrolidinylpyridin-2-one (dp2P) and -2-aminopyridine (dp2AP), prepared as part of a structure,activity profiling of pyrrolidino DNA in triplex binding, are deletion mutants of T and C, respectively. We found by Tm measurements that neither modification increased triplex binding efficiency relative to the iso-C- and -U-containing pyrrolidino TFOs. These experiments clearly show that the C4 carbonyl function, although important for triplex binding through indirect contributions in general, is not responsible for the differential binding of the latter two aminonucleosides and suggest that TFO conformation is more important. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Silver versus Gold Catalysis in Tandem Reactions of Carbonyl Functions onto Alkynes: A Versatile Access to Furoquinoline and Pyranoquinoline CoresCHEMISTRY - A EUROPEAN JOURNAL, Issue 19 2007Thomas Godet Abstract An efficient and versatile tandem process of acetalization and cycloisomerization reactions has been developed for the reactions of 1-alkynyl-2-carbonylquinoline substrates. The reaction occurs thanks to AuI and AgI catalysis. Silver(I) catalysis has been extensively studied (11 different silver species) on a broad range of quinoline derivatives (variation of alkyne substituent, of carbonyl function and of nucleophiles), leading to a variety of furoquinoline and pyranoquinoline moieties. An insight is given for the presumed mechanism along with DFT-B3,LYP/6,31G** calculations to address the 6- endo and 5- exo regioselectivities observed. [source] Woody Pretzels: Spirocycles from Vetiver to Patchouli and Georgywood®CHEMISTRY & BIODIVERSITY, Issue 6 2008Philip Kraft Abstract This review, including new experimental results, is the summary of a talk at the RSC/SCI conference ,flavours & fragrances 2007' in London, Imperial College, 24,26 September, 2007. Though the third dimension of the receptor models of J.,E. Amoore rarely was exceeding 4,Å, the world of woody odorants such as (+)-cedrol (3; cedarwood), (,)-khusimone (4; vetiver), and (,)-patchoulol (5; patchouli) is anything but flat. Any tricyclic skeleton with a zero-bridge contains a spirocyclic ring system determining its 3D structure, so spirocycles (spira, Lat. pretzel) are the fastest access to the third dimension. In the vetiver family, a spirocyclic mimic 9 of (,)-khusimone (4) was first discovered by chance by Büchi in 1976, and also by chance, we obtained another system, 12, with a characteristic vetiver smell by tandem- Rupe,Nazarov reaction of alkyne diols. A 5-Å distance between a quaternary C-atom and a carbonyl group (or alternative HB acceptor) with an , -methyl or methylene branching is proposed to be the key to their vetiver odor. Upon scale-up of one of these odorants, 24, we discovered a very powerful (0.067,ng/l) impurity with a most typical patchouli scent: the spirocyclic, sterically crowded hydroxy ketone 33 , a most unusual structure for a patchouli odorant. Several spirocyclic hydroxy ketone analogs, also with inverted ring systems such as in 70 and 84, provided new insights into the structure,odor correlation of this family. A superposition analysis indicated the carbonyl function of the hydroxy ketone to overlay on the geminal dimethyl motive of (,)-patchoulol. And indeed, the corresponding hydroxy ketone of patchoulol, 59, synthesized in 13 steps from Cyclal C (63), also emanated a patchouli odor. Finally, the synthesis and olfactory properties of twelve rigid spirocyclic analogs, 95,97, 99,102, and 106,110, of Georgywood® (91) are presented that highlight stereochemical requirements for woody odorants and raise doubts about an , -helical binding motive postulated by Hong and Corey. [source] Lactic Acid-Based Functionalized Polymers via Copolymerization and Chemical ModificationMACROMOLECULAR BIOSCIENCE, Issue 3 2004Benjamin Saulnier Abstract Summary: Poly(lactic acid) polymers (PLA) are presently the most attractive compounds in the field of artificial degradable and biodegradable polymers. In order to enlarge the family, and thus the range of accessible properties, stereocopolymers and copolymers with various co-monomers have been synthesized. However, very few are functionalized, i.e. include functional groups attached to the main chains or as part of the side chains. In the search for degradable PLA-type polymers bearing functional groups to serve as intermediates for further chemical modifications, we are exploring two different routes. The first one is copolymerization with a protected hydroxyl-bearing lactide-type monomer, namely 3-(1,2,3,4-tetraoxobutyldiisopropylidene)dioxane-2,5-dione. The second route consists of the formation of a carbanionic site in the , -position to intrachain carbonyl functions by using lithium N,N -diisopropylamide followed by the coupling of electrophiles. Recent advances in this search are presented using several examples. In particular, it is shown that OH-functionalized PLA-type macromolecules can be made fluorescent by chemical coupling. It is also shown that substituents can be attached to PLA-type macromolecules in solution or to the surface of PLA-based devices selectively. Example of chemical modifications of hydroxyl-bearing PLA-type polymers derived from gluconic and glycolic acids (via gluconolactone) and lactic acid (via lactide). [source] Thermo-Responsive Organic/Inorganic Hybrid Hydrogels based on Poly(N -vinylcaprolactam)MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2003Wouter Loos Abstract A new type of ,intelligent' hydrogels has been developed in the form of organic/inorganic hybrid materials by making use of the sol-gel technology. Poly(N -vinylcaprolactam) (PVCL) has been incorporated in these materials for its thermo-responsive properties. The synthesis of the hybrid hydrogels was achieved by the in situ formation of an inorganic silica phase in the presence of an aqueous solution of high molecular weight PVCL. This methodology results in the preparation of micro-heterogeneous systems in which silica particles of nanometer dimensions act as physical cross-links for the PVCL molecules. Hydrogen bonds between the remaining non-condensed silanol groups and the PVCL carbonyl functions, together with physical entanglements, are responsible for the strong interactions between the organic and inorganic phases. Stress-strain tests on highly swollen materials demonstrated that the unique structure of these thermo-responsive hybrid hydrogels improves the mechanical stability to a great extent as compared to conventional hydrogels. Transmission measurements demonstrate that the presence of the inorganic phase does not influence the cloud point temperatures of PVCL significantly. On the other hand, the response of the reinforced hybrid hydrogels to temperature becomes less pronounced for increasing silica fractions. The reversibility of the swelling/deswelling process has been demonstrated by swelling experiments as a function of temperature. PVCL/SiO2 hybrid hydrogels. [source] (±)-3-Oxocyclopentanecarboxylic acid: the smallest keto acid known to aggregate by catemeric hydrogen bondingACTA CRYSTALLOGRAPHICA SECTION C, Issue 12 2006Muhammad H. Malak The title compound, C6H8O3, is the smallest keto acid yet found to aggregate in the solid as acid-to-ketone hydrogen-bonded catemers. Four translational chains pass through the cell in the a direction [O,O = 2.6915,(14),Å and O,H,O = 166°]. Two intermolecular C,H,O close contacts exist, involving both carbonyl functions. [source] Highly Selective Hydrogenation of Carbon,Carbon Multiple Bonds Catalyzed by the Cation [(C6Me6)2Ru2(PPh2)H2]+: Molecular Structure of [(C6Me6)2Ru2(PPh2)(CHCHPh)H]+, a Possible Intermediate in the Case of Phenylacetylene HydrogenationCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2007Mathieu J.-L. Abstract The dinuclear cation [(C6Me6)2Ru2(PPh2)H2]+ (1) has been studied as the catalyst for the hydrogenation of carbon,carbon double and triple bonds. In particular, [1][BF4] turned out to be a highly selective hydrogenation catalyst for olefin functions in molecules also containing reducible carbonyl functions, such as acrolein, carvone, and methyljasmonate. The hypothesis of molecular catalysis by dinuclear ruthenium complexes is supported by catalyst-poisoning experiments, the absence of an induction period in the kinetics of cyclohexene hydrogenation, and the isolation and single-crystal X-ray structure analysis of the tetrafluoroborate salt of the cation [(C6Me6)2Ru2(PPh2)(CHCHPh)H]+ (2), which can be considered as an intermediate in the case of phenylacetylene hydrogenation. On the basis of these findings, a catalytic cycle is proposed which implies that substrate hydrogenation takes place at the intact diruthenium backbone, with the two ruthenium atoms acting cooperatively in the hydrogen-transfer process. [source] | |||||||||||||