Ozonolytic cleavage of cycloalkenes to terminally differentiated products

Conditions are reported which convert cycloalkenes to terminally differentiated products through the intermediacy of α-alkoxy hydroperoxides.     

Regioselective ozonolytic cleavage of unsymmetric cycloalkenes

Aldehyde 2 was prepared in a one-pot sequence from olefin 12; olefin 6 did not react similarly. Possible reasons for the differences are discussed.     

Conjugate addition/Ireland-Claisen rearrangements of allyl fumarates: simple access to terminally differentiated succinates

The conjugate addition of dialkylzinc reagents to allyl fumarates with subsequent Ireland-Claisen rearrangement has been accomplished yielding substituted unsymmetrical succinic acid derivatives. This one-pot reaction creates two new carbon-carbon bonds at contiguous stereogenic centers. The reaction proceeds for several alkylzinc reagents and substituted allyl fumarates. The products contain distinguishable functional handles for further manipulation.     

Ru-catalyzed cyclization of terminal alkynals to cycloalkenes

Cycloalkenes can be efficiently prepared by a new Ru-catalyzed cyclization of terminal alkynals. Under appropriate conditions, cycloisomerizations to conjugated aldehydes may be observed. Both processes involve catalytic Ru vinylidenes.     

Surface amplification of invasive cleavage products

A major focus of current efforts in genomics is to elucidate the genetic variations extent within the human population, and to study the effects of these variations upon the human system. The most common type of genetic variations are the single nucleotide polymorphisms (SNPs), which occur every 500-1000 nt in the genome. Large-scale population association studies to study the biological or medical significance of such variations may require the analysis of hundreds of thousands of SNPs on thousands of individuals. We are pursuing development of an approach to large-scale SNP analysis that combines the specificity of invasive cleavage reactions with the parallelism of high density DNA arrays. A surface-immobilized probe oligonucleotide is specifically cleaved in the presence of a complementary target sequence in unamplified human genomic DNA, yielding a 5' phosphate group. High sensitivity detection of this reaction product on the surface is achieved by the use of rolling circle amplification, with an approximate concentration detection limit of 10 fM target DNA. This combination of very specific surface cleavage and highly sensitive surface detection will make possible the rapid and parallel analysis of genetic variations across large populations.     

Ring opening-cross metathesis of unstrained cycloalkenes

Unstrained cycloalkenes undergo ruthenium-catalysed ring opening-cross metathesis reactions with simple alpha, beta-unsaturated carbonyl compounds under mild conditions.     

Asymmetric 1,3-dipolar cycloadditions of chiral carboxyloyl nitrile oxides to cycloalkenes

Asymmetric 1,3-dipolar cycloadditions of chiral carboxyloyl nitrile oxides derived from (2R)-bornane-10,2-sultam, (1R)-8-phenylmenthol, N,N-dicyclohexyl-10-sulfamoyl-(2R)-isoborneol, and 7,7-dimethylnorbornane-(1S,2R)-oxazolidinone to four cycloalkenes, leading to the corresponding 2-isoxazolines in both moderate yields and diastereoselectivities, are presented. All cycloadducts were converted into the corresponding alcohols, which were used for the determination of enantiomeric purity via chiral gas chromatography. In the case of the six-membered ring cycloadduct, the absolute configuration was determined by X-ray analysis.     

Ozonolytic determination of double-bond positions in olefins by gas chromatography

Summary Olefinic compounds are reacted with ozone in CCl₄/CH₃OH solution, yielding specific cleavage products, from which the original position of the double bond can be deduced. By reduction with dimethylsulfide the resulting methoxyhydroperoxides are converted into aldehydes and ketones, which are determined by temperature-programmed gas chromatography on silicone columns. The lower compounds (C₁-C₁₀) are analyzed as dinitrophenylhydrazones, the less volatile higher ones as such. 100% yields were obtained for monoolefins of different structures and chain lengths (up to C₃₀).

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Ozonolytische Bestimmung von Doppelbindungen in Olefinen durch Gas-Chromatographie

Zusammenfassung Die Olefine werden in CCl₄/CH₃OH-Lösung mit Ozon behandelt, wodurch spezifische Spaltprodukte entstehen, aus denen man die ursprüngliche Lage der Doppelbindung ableiten kann. Die entstandenen Methoxyhydroperoxide werden durch Reduktion mit Dimethylsulfid zu Aldehyden und Ketonen umgesetzt, die durch temperaturprogrammierte Gas-Chromatographie an Siliconsäulen analysiert werden. Die niedrigeren (C₁-C₁₀) Verbindungen werden als Dinitrophenylhydrazone bestimmt, die weniger flüchtigen höheren als solche. Für aliphatische Monoolefine verschiedener Struktur und Kettenlänge (bis C₃₀) wurden 100%ige Ausbeuten erhalten.

Lecture presented at Euroanalysis I Conference, 28. 8.–1. 9. 1972 in Heidelberg, Germany.     

Stereochemistry of free radical additions of methanol and acetaldehyde to perfluorinated cycloalkenes

γ-Ray and peroxide-initiated additions of methanol and acetaldehyde to perfluorocyclo-butene (3), -pentene (4), and -hexene (5) gave mixtures of stereo-isomers in most cases. Stereospecific $\text{cis}$-addition of acetaldehyde to (5) occurs under γ-initiation. A simple ¹⁹F n.m.r. method is advanced to distinguish the geometric isomers.     

Aluminum oxide catalyzed isomerization of acylated cycloalkenes

A homologous series of cyclic olefins and their corresponding 1-methyl derivatives were acylated using acetic anhydride/zinc chloride system. The resulting mixtures were, after appropriate analysis, isomerized quantitatively to the conjugated enones by adsorption on neutral alumina. A detailed, general experimental procedure is given.     

Carotenoids and their cleavage products: biosynthesis and functions

This review focuses on plant carotenoids, but it also includes progress made on microbial and animal carotenoid metabolism to better understand the functions and the evolution of these structurally diverse compounds with a common backbone. Plants have evolved isogenes for specific key steps of carotenoid biosynthesis with differential expression profiles, whose characteristic features will be compared. Perhaps the most exciting progress has been made in studies of carotenoid cleavage products (apocarotenoids) with an ever-expanding variety of novel functions being discovered. This review therefore covers structural, molecular genetic and functional aspects of carotenoids and apocarotenoids alike. Apocarotenoids are specifically tailored from carotenoids by a family of oxidative cleavage enzymes, but whether there are contributions to their generation from chemical oxidation, photooxidation or other mechanisms is largely unknown. Control of carotenoid homeostasis is discussed in the context of biosynthetic and degradative reactions but also in the context of subcellular environments for deposition and sequestration within and outside of plastids. Other aspects of carotenoid research, including metabolic engineering and synthetic biology approaches, will only be covered briefly.     

Convenient one-pot synthesis of thiosugars and their efficient conversion to polyoxygenated cycloalkenes

A convenient synthesis of polyoxygenated tetrahydrothiopyrans and thiepanes from various alditol derivatives with xylo, ribo, manno, gluco, galacto, and fuco configurations is described. The preparation started from the corresponding partially protected alditols and proceeded in a ‘one-pot’ manner to afford the final products in 80%–95% yield. Furthermore, thiosugar compounds 2b, 2d, and 2g were converted to the optically pure polyoxygenated cycloalkenes through Ramberg–Backlund reaction in moderate to good overall yield. The procedures can be used for the preparation of polyoxygenated thiosugars and cycloalkenes on a relatively large scale.     

Ozonolytic transformations of olefinic derivatives of L-menthol and ricinolic acid

Ozonolysis and reduction of olefinic derivatives of ricinolic acid and L-menthol were studied using hydroxylamine hydrochloride and sodium trisacetoxyborohydride to reduce the peroxide products. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 515–518, November–December, 2006.     

Mass-spectrometric study of the cleavage products of 3,4-epoxytetrahydropyrans by amines

Conclusions Only 4-methyl-3-amino-4-hydroxytetrahydropyrans are formed when the oxide ring of 4-methyl-3,4-epoxytetrahydropyran is opened by ammonia and amines. The structural isomers of 4-amino-3-hydroxy-and 3-amino-4-hydroxytetrahydropyran are formed in the analogous reaction of the unsubstituted 3,4-epoxy-tetrahydropyran, the mutual arrangement of the substituents in which was determined on the basis of analyzing the mass spectra.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 636–639, March, 1971.     

Impact of neutral and acidic species on cycloalkenes nucleation

Non-covalent hydrogen bond interactions between the π cloud of cycloalkenes and three atmospheric common nucleation precursors (H₂S, H₂O, and MeOH) have been investigated using DFT and CCSD(T). The structures and the energies of the 1:1 and 1:2 adducts were computed with the B3LYP-D3 method. The analysis of the investigated electronic properties and geometric parameters shows that cyclohexene is a stronger hydrogen bond acceptor than cyclopentene, then followed by 1,4-cyclohexadiene and 1,3-cyclohexadiene. Comparable red shifts of the OH-/SH-stretching vibrational frequencies were noticed for the studied clusters. Increasing the ring size enhances the hydrogen bond interaction, and increasing the π delocalization decreases the hydrogen bond interactions. This is further confirmed by Bader’s quantum theory of atoms in molecules. The nonadditivity effects were observed in the trimolecular complexes. All the complexes were analyzed by energy decomposition analysis to divide the interaction energy into individual components. Furthermore, the dipole moments and atmospheric implications were also investigated.

     

DFT study on RuII‐catalyzed cyclization of terminal alkynals to cycloalkenes

The reaction mechanism of [CpRu(MeCN)₃]PF₆‐catalyzed cyclization of terminal alkynals 1 to cycloalkenes 2 was investigated by means of density functional methods combined with polarizable continuum models. Calculations indicate that the coordination of the cationic catalyst [CpRu(CH₃CN)₂]⁺ to the carbon–carbon triple bond of the substrate 1 enhances the electrophilicity of alkynyl group, and the subsequent nucleophilic attack of the carbonyl oxygen to the electron‐deficient alkyne forms ate complex IM2 , which would further isomerize into 2H‐oxete complex IM3 . Then a replacement of MeCN by AcOH occurs, followed by two proton‐migrations, which leads to a Fischer‐type carbene complex IM6 . Finally, a decarbonylation takes place leading to cycloalkene 2 . The terminal alkynal is activated by its combination with ruthenium, which leads to a decrease in the natural bond orbital energy of π*_(C1?C2). The four‐membered ring formation is the rate‐controlling step. However, AcOH helps proton shift through coordination with metal center and decreases the reaction energy barriers. Throughout the reactions, all the Ru^II complexes obey the 18‐electron‐rule. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009