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C=C Double Bond (c=c + double_bond)
Selected AbstractsCatalytic cleavage of methyl oleate or oleic acidEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 1 2010Angela Köckritz Abstract Different reaction pathways are discussed for the Os-catalyzed oxidation of methyl oleate and oleic acid using O2/aldehyde as oxidation system. Monomethyl azelate and pelargonic acid were the main products obtained in yields of approximately 50,70% starting from methyl oleate. Besides, varying amounts of methyl 9,10-epoxystearate and methyl 9,10-dihydroxystearate were found as by-products. Azelaic acid and pelargonic acid were obtained exclusively from oleic acid used as reactant. Some mechanistic considerations led to the conclusion that the observed products are formed in parallel reaction paths. The effective oxidant for the scission of the C=C double bond seems to be very likely an in situ formed peracid generated by Os-catalysis from O2/aldehyde. Additional investigations concerning the cleavage of oleic acid and methyl oleate with in situ formed performic acid from H2O2/formic acid corroborate this assumption. [source] Asymmetric Synthesis of a Novel Conformationally Constrained D -Lysine Analogue with a Piperidine SkeletonEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2008Pablo Etayo Abstract A practical asymmetric synthesis of enantiomerically pure(2R,4R)-1-(tert -butoxycarbonyl)-4-[2-(methoxycarbonylamino)ethyl]pipecolic acid starting from easily accessible (R)-2-[(S)-1,2-bis(benzyloxy)ethyl]-1-[(S)-1-phenylethyl]-4-piperidone in around 33,% overall yield has been performed. The efficiency of the synthetic strategy developed for the synthesis of this novel conformationally constrained D -lysine analogue relies on the high-yielding Wadsworth,Emmons reaction of a 2-substituted 4-piperidone and the diastereoselective reduction of the exocyclic C=C double bond at the 4-position of the piperidine ring.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] 6,-Hydroxy-5,-methyl-20-oxo-19-norpregn-9(10)-en-3,-yl acetateACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009R. M. A. Pinto In the title compound, C23H34O4, which is an intermediate in the synthesis of pregnane derivatives with a modified skeleton that show potent abortion-inducing activity, the conformation of ring B is close to half-chair due to the presence of both the C=C double bond and the axial 5,-methyl group. Rings A and C have conformations close to chair, while ring D has a twisted conformation around the bridgehead C,C bond. Molecules are hydrogen bonded via the hydroxyl and acetoxy groups into infinite chains. Quantum-mechanical ab initio Roothan Hartree,Fock calculations show that crystal packing might be responsible for the low values of the angles between rings A and B, and between ring A and rings C and D, as well as for a different steric position of the methyl ketone side chain compared to the geometry of the free molecule. [source] 3,3,4,4,5,5-Hexafluoro-1-(2-methoxyphenyl)-2-[5-(4-methoxyphenyl)-2-methyl-3-thienyl]cyclopent-1-ene: a photochromic compoundACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009Congbin Fan The photochromic title compound, C24H18F6O2S, has thienyl and aryl substituents on the C=C double bond of the shallow half-chair-shaped cyclopentene ring. The planes of the two substituent rings are inclined to that of the cyclopentene ring, with dihedral angles between the mean plane of the cyclopentene ring and those of the phenylene and thienyl rings of 51.2,(1) and 51.3,(1)°, respectively. The molecule adopts an antiparallel conformation, with a distance between the two photoreactive C atoms of 3.717,(2),Å. [source] Asymmetric Dihydroxylation of ,,,-Unsaturated Carboxylic Esterswith Trisubstituted C=C Bonds , Enantioselective Syntheses of Trisubstituted ,-ButyrolactonesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 9 2006Tobias Kapferer Abstract ,,,-Unsaturated esters with stereodefined trisubstitued C=C double bonds were prepared by the Arndt,Eistert homologation of ,,,-unsaturated carboxyl halides, by two-step methoxycarbonylation of allylbarium reagents, by deconjugation of ,,,-unsaturated esters, and by Horner,Wadsworth,Emmons variants of the Stobbe condensation. Sharpless asymmetric dihydroxylation of the ,,,-unsaturated esters, followed by spontaneous cyclization, afforded ,-hydroxy-,-lactones in moderate to good yields and with enantiomeric excesses of up to 97,%. Similarly, tetrahydroxy-,-lactones were obtained from diunsaturated esters; these lactones were converted into a bislactone and an unsaturated ,-hydroxy ,-lactone. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Two isomeric cucurbitane derivativesACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2009Maciej Kubicki Two isomeric cucurbitane derivatives, 3,,7,,11,-triacetoxycucurbit-5(10)-ene, (I), and 3,,7,,11,-triacetoxy-5,-cucurbit-1(10)-ene, (II), both C36H58O6, have their single endocyclic C=C double bonds in different positions. This results in differences in the conformation of the four-ring system, which is close to a half-chair/half-chair/chair/half-chair arrangement in (I) and to a half-chair/twist-boat/boat/half-chair arrangement in (II). The orientation of some of the substituents is also different; the 3,-acetoxy group is in an equatorial position in (I) but in an axial position in (II), while the 11,-acetoxy group occupies an axial position in (I) and an equatorial position in (II). The asymmetric unit of (I) contains two symmetry-independent molecules which do not differ significantly, being related by a pseudo-twofold axis of symmetry. In both structures, the aliphatic chain fragments are disordered and the disorder persists at lower temperatures. [source] | ||||||||||