- Lewis Acid Catalysis of the Ene Addition of Chloral and Bromal to Olefins; Stereochemical and Mechanistic Studies
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The Lewis acid catalysed ene additions of chloral and bromal to alkenes are completely regiospecific, moderately regioselective, and often highly stereoselective.Diastereoselectivity in the addition to (-)-β-pinene was a function of the Lewis acid, and with TiCl4 essentially quantitative asymmetric induction was observed.The stereochemical phenomena are explained satisfactory by assuming the active enophiles possess transoid structures such as (1), that a concerted or rapid stepwise mechanism operates, and that product formation occurs predominantly through the least hindered encounter complex of the olefin and (1).In the case of 2-methylbut-2-ene, however, there is some evidence for an additional stereoelectronic contribution, the 'cis-effect'.Stereochemical assignements are supported by X-ray structural data.Ketones, hydrohalogenated ene adducts, or rearrangement products are formed (mainly in the addition to olefins of moderate reactivity) indicating the participation of Friedel-Crafts type dipolar intermediates.The ene adducts themselves could be formed via dipolar intermediates or in competing 'concerted' reactions; the stepwise mechanism must operate in some reactions because of the observation of Wagner-Meerwein rearrangements.Olefin reactivity over the series, measured by the competitive technique, towards chloral-AlCl3 showed a ca. 900-fold variation in rate; 'ene' reactivity decreases more steeply.
- Benner, Jill P.,Gill, G. Bryon,Parrott, Stephen J.,Wallace, Brian,Begley, Michael J.
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Read Online
- Synthesis and Biomimetic Rearrangement of a Chiral Diterpene Dioxide
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As part of a biomimetic approach towards the marine triterpene teurilene (2), the synthesis of the chiral diepoxide 3 is described.Aiming at the synthesis of the squalene tetraepoxide 1, double Sharpless epoxidation led to the intermediate bisglycidic alcohol 7 being subject to a stereochemical analysis.
- Lindel, Thomas,Franck, Burchard
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Read Online
- Gastric cytoprotective activity of 2-cyclopenten-1-one and related compounds
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The cytoprotective activity of the isolated functional groups of several sesquiterpene lactones is reported. Among them the highest activity is shown by α-methylen-γ-butyrolactone and 2-cyclopenten-1-one. The activity shown by those Michael acceptors with a β carbon hindered by an alkyl substituent was always lower or almost null. A three-way mechanism of action is proposed: a) reduced glutathione synthesis, b) prostaglandin synthesis and c) mucosal glycoprotein synthesis.
- Maria,Wendel,Guardia,Guzman,Pestchanker,Guerreiro,Giordano
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Read Online
- Well-defined polymers from biosourced monomers: The case of 2-(methacryloyloxy)ethyl tiglate
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Tiglic acid esters are naturally derived olefins of pleasant odor but incapable of undergoing free-radical polymerization due to the steric hindrances conferred by the β-methyl group. In an effort to incorporate these green olefins in well-defined (co)polymers, we first established that methyl tiglate, the simplest tiglic acid ester, could not be polymerized using controlled polymerization techniques either, and we then introduced it in a methacrylate monomer, 2-(methacryloyloxy)ethyl tiglate (MAET), which could smoothly undergo group transfer polymerization (GTP) to yield linear polymers of narrow molecular weight distributions. Subsequently, amphiphilic and double-hydrophobic block copolymers, as well as a star polymer of MAET were obtained by its sequential GTP with 2-(dimethylamino)ethyl methacrylate, methyl methacrylate, and ethylene glycol dimethacrylate, respectively. Finally, polyMAET was selectively oxidized.
- Kassi, Eleni,Patrickios, Costas S.
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Read Online
- Second-Generation meta-Phenolsulfonic Acid-Formaldehyde Resin as a Catalyst for Continuous-Flow Esterification
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A second-generation m-phenolsulfonic acid-formaldehyde resin (PAFR II) catalyst was prepared by condensation polymerization of sodium m-phenolsulfonate and paraformaldehyde in an aqueous H2SO4 solution. This reusable, robust acid resin catalyst was improved in both catalytic activity and stability, maintaining the characteristics of the previous generation catalyst (p-phenolsulfonic acid-formaldehyde resin). PAFR II was applied in the batchwise and continuous-flow direct esterification without water removal and provided higher product yields in continuous-flow esterification than any other commercial ion-exchanged acid catalyst tested.
- Hu, Hao,Ota, Hajime,Baek, Heeyoel,Shinohara, Kenta,Mase, Toshiaki,Uozumi, Yasuhiro,Yamada, Yoichi M. A.
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supporting information
p. 160 - 163
(2020/01/02)
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- The acylated piperazine compound and use thereof
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The present invention relates to acylated piperazine compound and its use, further relates to the pharmaceutical composition. The compound of the invention or the pharmaceutical composition can be used as dipeptidyl peptidase - IV (DPP - IV) inhibitors.
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Paragraph 0167; 0262-0267
(2019/05/16)
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- BIPOLAR TRANS CAROTENOID SALTS AND USES THEREOF
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PROBLEM TO BE SOLVED: To provide compounds useful in improving diffusivity of oxygen between red blood cells and body tissues in mammals including humans. SOLUTION: There is provided a compound which has a structure represented by YZ-TCRO-ZY and is not trans sodium crocetinate [where, Y is a cation; Z is a polar group which is associated with the cation; and TCRO is trans carotenoid skeleton], and preferably, Y is a monovalent metal ion selected from the group consisting of Na+, K+ and Li+, or is an organic cation selected from the group consisting of R4 N+ and R3S+ [R is H, or CnH2n+1(n is 1 to 10)]. SELECTED DRAWING: None COPYRIGHT: (C)2018,JPO&INPIT
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Paragraph 0083; 0134; 0188
(2018/10/26)
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- Characterization of the Saffron Derivative Crocetin as an Inhibitor of Human Lactate Dehydrogenase 5 in the Antiglycolytic Approach against Cancer
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Inhibition of lactate dehydrogenase (LDH) represents an innovative approach to tackle cancer because this peculiar glycolytic metabolism is characteristic of most invasive tumor cells. An investigation into the biological properties of saffron extracts led to the discover of their LDH-inhibition properties. In particular, the most important saffron components, crocetin, was found to inhibit LDH (IC50 = 54.9 ± 4.7 μM). This carotenoid was independently produced by chemical synthesis, and its LDH-inhibition properties manifested via its antiproliferative activity against two glycolytic cancer cell lines (A549 and HeLa, IC50 = 114.0 ± 8.0 and 113.0 ± 11.1 μM, respectively). The results described in this article suggest that saffron may be a helpful alimentary component in the prevention of cancer that potentially contributes to the efficacy of approved cancer therapies.
- Granchi, Carlotta,Fortunato, Serena,Meini, Serena,Rizzolio, Flavio,Caligiuri, Isabella,Tuccinardi, Tiziano,Lee, Hyang Yeon,Hergenrother, Paul J.,Minutolo, Filippo
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p. 5639 - 5649
(2017/07/26)
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- 3-PHOSPHOGLYCERATE DEHYDROGENASE INHIBITORS AND USES THEREOF
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The present invention provides compounds, compositions thereof, and methods of using the same.
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Paragraph 00429
(2017/10/06)
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- BIPOLAR TRANS CAROTENOID SALTS AND THEIR USE
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PROBLEM TO BE SOLVED: To provide trans carotenoid salt compounds useful for improving the diffusibility of oxygen between red blood cells and a body tissue in mammalian including human being, a method for producing them, a method for solubilizing them, and a method for using them. SOLUTION: There are provided compounds represented by the following formula, and are compounds not being trans sodium crocetinate: YZ-TCRO-ZY[Y denotes a cation; Z denotes a polar group coupled to the cation; TCRO denotes a trans carotenoid skeleton; preferably, as follows; Y denotes the monovalent metal ion of Na+,K+ or Li+ or R4 N+ or R3S+;R denotes H or CnH2n+1;n denotes the integer of 1 to 10;Z denotes a carboxyl group, a sulfuric acid group, a mono-phosphoric acid group, a di-phosphoric acid group, or a tri-phosphoric acid group; and TCRO denotes a group using isopronoid in which the single bond and double bond of straight chain carbon and carbon as exemplified by the following formula is repeated (X respectively independently denotes H, a straight chain/branched carbon chain substituted/non-substituted with 1 to 10C halogen or a halogen)]. SELECTED DRAWING: None COPYRIGHT: (C)2017,JPO&INPIT
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Paragraph 0100; 0134; 0187-0194
(2018/10/31)
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- Diamidocarbenes as versatile and reversible [2+1] cycloaddition reagents
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We describe the synthesis of a variety of cyclopropanes and epoxides by combining a readily accessible and isolable N,N-2-diamidocarbene with a range of structurally and electronically diverse olefins and aldehydes, including electron-rich derivatives. Surprisingly, the cyclopropanation and epoxidation reactions were discovered to be rapid and thermally reversible at relatively low temperatures, two features often desired for applications that utilize dynamic covalent chemistry. In addition, a diamidocyclopropane derivative prepared via this method was hydrolysed successfully to form the corresponding linear carboxylic acid in a metal-and carbon monoxide-free hydrocarboxylation reaction. As such, diamidocarbenes are expected to find utility in the synthesis of cyclopropanes, epoxides and their derivatives, as well as in dynamic covalent chemistry applications.
- Moerdyk, Jonathan P.,Bielawski, Christopher W.
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scheme or table
p. 275 - 280
(2012/06/18)
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- BIPOLAR TRANS CAROTENOID SALTS AND THEIR USES
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The invention relates to trans carotenoid salt compounds, methods for making them, methods for solubilizing them and uses thereof. These compounds are useful in improving diffusivity of oxygen between red blood cells and body tissues in mammals including humans.
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Page/Page column 45-46
(2008/06/13)
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- Stereocontrol in organic synthesis using silicon-containing compounds. Studies directed towards the synthesis of ebelactone A
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Several approaches to the synthesis of ebelactone A 2 are described, culminating in the synthesis of the benzenesulfonate of 2-epi-ebelactone A 161. All the approaches were based on three fragments A, B and C, originally defined in general terms in Scheme 1, but eventually used as the aldehyde 72, the allenylsilane 3 and the aldehyde 139, respectively. They were joined, first B with C, and then B+C with A. In the main routes to fragments A and C, the relative stereochemistry was controlled by highly stereoselective enolate methylations 66 → 67, 68 → 69, and 135 → 136, in each case anti to an adjacent silyl group, and by a highly stereoselective hydroboration of an allylsilane 137 → 138, also anti to the silyl group. The hydroxyl groups destined to be on C-3 and C-11 were unmasked by silyl-to-hydroxy conversions 69 → 70 and 138 → 139 with retention of configuration. The stereochemistry created in the coupling of fragment B to C was controlled by the stereospecifically anti SE2′ reaction between the enantiomerically enriched allenylsilane 3 and the aldehyde 139. The double bond geometry was controlled by syn stereospecific silylcupration 148 → 151, and preserved by iododesilylation 151 → 152 of the vinylsilane with retention of configuration, and Nozaki-Hiyama-Kishi coupling with the aldehyde 72 gave the whole carbon skeleton 153 of ebelactone A with the correct relative configuration, all of which had been controlled by organosilicon chemistry. In the steps to remove the superfluous allylic hydroxyl, an intermediate allyllithium species 156 abstracted the proton on C-2, and its reprotonation inverted the configuration at that atom. Other routes to the fragments A and C were also explored, both successful and unsuccessful, both silicon-based and conventional, and a number of unexpected side reactions were investigated.
- Archibald, Sarah C.,Barden, David J.,Bazin, Jerome F.Y.,Fleming, Ian,Foster, Colin F.,Mandal, Ajay K.,Mandal, Amit K.,Parker, David,Takaki, Ken,Ware, Anne C.,Williams, Anne R.B.,Zwicky, Anna B.
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p. 1051 - 1064
(2007/10/03)
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- Bipolar trans carotenoid salts and their uses
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The invention relates to trans carotenoid salt compounds, methods for making them, methods for solubilizing them and uses thereof. These compounds are useful in improving diffusivity of oxygen between red blood cells and body tissues in mammals including humans.
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- Biopolar trans carotenoid salts and their uses
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The invention relates to trans carotenoid salt compounds, methods for making them, methods for solubilizing them and uses thereof. These compounds are useful in improving diffusivity of oxygen between red blood cells and body tissues in mammals including humans.
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- Simple access to 2-methylalk-2-enoates and insect pheromones by zinc-promoted reduction of Baylis-Hillman-derived allylic bromides
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(E)-2-Methylacrylates are prepared in good yield and high stereoselectivity by zinc-promoted reduction of 2-(bromomethyl)alkenoates derived from Baylis-Hillman adducts. Synthesis of the male ant pheromone (E)-2,4-dimethyl-2- hexenoic acid was performed using this simple methodology. (E)-2-Methylacrylates are easily prepared by zinc-promoted reduction of 2-(bromomethyl)alkenoates derived from Baylis-Hillman adducts. Synthesis of the male ant pheromone (E)-2,4-dimethyl-2-hexenoic acid was performed using this simple methodology.
- Fernandes, Luciano,Bortoluzzi, Adailton J.,Sá, Marcus M.
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p. 9983 - 9989
(2007/10/03)
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- Stereospecific synthesis of chiral tertiary alkyl-aryl ethers via Mitsunobu reaction with complete inversion of configuration
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Mitsunobu reaction of chiral tertiary alcohol (S)-2 with phenol 3 provides the desired ether (R)-1 in moderate yields at elevated temperatures (80-100°C). The SN2 displacement pathway is evident by complete inversion of the (S)-alcohol to (R)-e
- Shi, Yao-Jun,Hughes, David L.,McNamara, James M.
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p. 3609 - 3611
(2007/10/03)
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- Control of regioselectivity by the lone substituent through steric and electronic effects in the nitrosoarene ene reaction of deuterium-labeled trisubstituted alkenes
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For the ene reaction of 4-nitronitrosobenzene (ARNO) with a variety of primary and secondary lone alkyl-substituted substrates, the twix/twin regioselectivity is constant at about 85:15. In contrast, for the lone tert-butyl group and for lone aryl substituents, the twix regioisomer is obtained exclusively. These regioselectivities have been rationalized in terms of steric interactions and coordination between the enophile and the substrates in the transition states of the first reaction step.
- Adam, Waldemar,Krebs, Oliver,Orfanopoulos, Michael,Stratakis, Manolis
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p. 8395 - 8399
(2007/10/03)
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- Didehydrogeranylgeranyl (ΔΔGG): A fluorescent probe for protein prenylation
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The first intrinsically fluorescent analog of geranylgeraniol, (2E,6E,8E,10E,12E,14E)-geranylgeraniol (all-trans-ΔΔGGOH·1) has been synthesized stereoselectively and shown to substitute for the geranylgeranyl (GG) moiety in prenyl transferase reactions and in protein-ligand binding assays. All-trans-ΔΔGGOH 1 showed blue fluorescence in methanol, with λex = 310 nm and λem = 410 nm (ε310 = 2.4 × 104 M-1 cm-1), but was only weakly fluorescent in aqueous solution. The prenyl transferase efficiency for ΔΔGGPP 2 as a substrate for yeast protein geranylgeranyl transferase (PGGTase-I) was 60% relative to that for GGPP. The binding of ΔΔGG-AcCysMe 3 to the recombinant Rho GTPase dissociation inhibitor (RhoGDI) had a KD of 15.1 ± 1.2 μM, 6-fold lower than the affinity of GG-AcCysMe. Thus, the ΔΔGG moiety is a novel fluorophore suitable for studying the interaction and subcellular localization of prenylated small GTPase proteins in signaling complexes. Copyright
- Liu,Prestwich
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- Synthesis of (7S,15S)- and (7R,15S)-dolatrienoic acid
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The stereospecific synthesis of (7S,15S)- and (7R,15S)-dolatrienoic acids (2) was achieved using an approach consisting of 16 linear steps. The C-11-C-16 unit was prepared in seven steps from ethyl (S)lactate and coupled using a trans-selective Wittig - Schlosser reaction to the C-7-C-10 fragment. Chirality at the C-7 position was introduced using an Evan's-type chiral auxiliary in a cobalt-mediated Reformatsky reaction to give the (3S,11S)-aldehyde 24. Subsequent Wittig reaction with a phosphonium salt derived in three steps from tiglic acid gave (7S,15S)-dolatrienoic acid, one of the four possible diastereoisomers of the nonpeptide portion of the strong Cancer cell growth inhibitory cyclodepsipeptide dolastatin 14 (1). A second diastereoisomer, (7R,15S)-dolatrienoic acid, was synthesized employing chiral oxazolidinone 21 by an analogous synthetic route.
- Duffield, Jonathan J.,Pettit, George R.
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p. 472 - 479
(2007/10/03)
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- Analytical Applications of Raman Spectroscopy in Organic Chemistry: Influence of the Position, Stereochemistry and Substitution Pattern of the Double Bond on the ν(C=C) and ν(sp2CH) Stretching Bands in the Raman Spectra of Alkenyl Methyl Ethers
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The Raman spectra of 29 alkenyl methyl ethers, CnH(2n-1)OCH3, of diverse structure containing up to seven carbon atoms are reported and discussed. All these spectra contain a strong band in the region 1640-1680 cm-1 associated with the stretching vibration of the C=C double bond. Reliable correlations are found between the wavenumber of this band and the position, stereochemistry and substitution pattern of the double bond the band is at higher wavenumber for ethers containing a di- or tri-substituted bond than for those with a monosubstituted bond and at higher wavenumber for trans than cis-stereoisomers. One or more bands in the range 2995-3080 cm-1 associated with the stretching vibration(s) of the sp2C-H bond(s) are also evident in the spectra of most of the ethers, but these bands are sometimes obscured by the stronger bands corresponding to stretching vibrations of the sp3C-H bonds at slightly lower wavenumber (generally below ca. 2950 cm-1). Correlations involving the number and position(s) of these band provide confirmatory evidence on the substitution pattern and stereochemistry of the C=C group. Unequivocal assignment of the symmetric and asymmetric C-H stretching vibrations of the important terminal C=CH2 entity is possible on the basis of these studies; these conclusions are supported by analysis of the Raman spectrum of the deuterium labelled ether CD2=CH(CH2)3OCH3.
- Bowen, Richard D.,Edwards, Howell G. M.,Farwell, Dennis W.,Rusike, Irene,Saunders, Darren M.
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p. 1901 - 1918
(2007/10/03)
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- Total synthesis of sollasin a and sollasin d via photocycloaddition of methyl 2,4-dioxopentanoate to methyl E-2-methyl-2-butenoate
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Starting from photocycloaddition of methyl 2,4-dioxopentanoate to methyl tiglate, an electron-deficient olefin, methyl-migrated monocyclofarnesyl sesquiterpenoids, d,l-sollasin a and d, antibacterial compounds, were synthesized.
- Hatsui, Toshihide,Taga, Masashi,Mori, Akira,Takeshita, Hitoshi
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p. 113 - 114
(2007/10/03)
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- Structure-cytoprotective activity relationship of simple molecules containing an α,β-unsaturated carbonyl system
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In previous reports we attributed the cytoprotective activity of several sesquiterpene lactones to the presence of a nonhindered electrophilic acceptor in their structure. We suggested that the mechanism of protection would be, at least in part, mediated through a reaction between the electrophilic acceptor and the sulfhydryl-containing groups of the mucosa. We report here the gastric cytoprotective effect of simple molecules containing an α,β-unsaturated carbonyl group. In the present paper, we undertake the study of molecular accessibility and molecular shape, in addition to conformational, electronic, and steric factors. Our results helped to establish two important facts connecting chemical structure with cytoprotective effect. Firstly, an adequate molecular accessibility appears to be necessary to produce the biological response, and secondly, the α,β- unsaturated carbonyl system has to be included in a cyclic structure or, at least, in the proximity of a cyclic system.
- Rodríguez, Ana M.,Enriz, Ricardo D.,Santagata, Luis N.,Jáuregui, Esteban A.,Pestchanker, Mauricio J.,Giordano, Oscar S.
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p. 1827 - 1834
(2007/10/03)
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- Reactions of phenyltriazolinedione with alkenes. Stereochemistry of methanol adducts to aziridinium imide intermediates
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The addition of 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) and the stereochemistry of methanol/PTAD adduct formation with cis- and trans-2-butenes, 1-methylcyclopentene, (E)-2-methyl-2-butene-1,1,1-d3 and substituted indenes (indene, 2-methylindene, 2,3-dimethylindene) have been investigated. There is no loss of stereochemistry in the addition of MeOH and PTAD to butenes, 1-methylcyclopentene, 2-methyl-2-butene, and indene. However, in methyl-substituted indenes 9 and 14, loss of stereochemistry at the reaction center is observed. An aziridinium imide (AI) is proposed as an intermediate in all these systems. The stability of the AI intermediate and its equilibration with an open zwitterion depend on the particular system. Only in the benzylically-stabilized tertiary indenes is the open zwitterion stable enough to cause loss of stereochemistry.
- Smonou, Ioulia,Khan, Saeed,Foote, Christopher S.,Elemes, Yiannis,Mavridis, Irene M.,Pantidou, Ariadne,Orfanopoulos, Michael
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p. 7081 - 7087
(2007/10/02)
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- Ruthenium Complex-Catalyzed Carbonylation of Allylic Compounds
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Allylic alkyl carbonates are carbonylated under 40 atm of carbon monoxide at 100-120 deg C in the presence of a catalytic amount of Ru3(CO)12/1,10-phenanthroline to give α,β- or β,γ-unsaturated esters in good to high yields.For example, cinnamyl methyl carbonate afforded the corresponding β,γ-unsaturated esters, methyl trans-4-phenyl-3-butenoate (1) in 93percent yield.The regioselectivity in the carbonylation of crotyl methyl carbonate is unusual and it depends on the carbon monoxide pressure.The more sterically hindered carbon (γ-carbon) is predominantly carbonylated at 20-50 atm.When the reaction of cinnamyl methyl carbonate was performed at elevated temperature (150 deg C) without 1,10-phenanthroline, the dimer of 1, dimethyl 3-benzyl-2-(trans-2-phenylvinyl)glutarate, was obtained in 56percent yield.In the presence of secondary amines, allylic alkyl carbonates were carbonylated mainly at α-carbon to give α,β- or β,γ-unsaturated amides in high yields.
- Mitsudo, Take-aki,Suzuki, Nobuyoshi,Kondo, Teruyuki,Watanabe, Yoshihisa
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p. 7759 - 7765
(2007/10/02)
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- Stereoselectivity and Generality of the Palladium-Catalysed Cyclopropanation of α,β-Unsaturated Carboxylic Acids Derivatized with Oppolzer's Sultam
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A series of α,β-unsaturated carboxylic acids derivatized with camphorsultam 1 a s a chiral auxiliary has been stereoselectively cyclopropanated. the selectivity of the reaction produces cyclopropanated products with the 1R,2R absolute configuration as indicated by the optical rotations as well as by an X-ray structure determineation.The temperature dependence of the reaction was studied with three substrates. the highest stereoselectivity was obtained at temperatures above 25 deg C.Branching at the α- or β-carbons disfavours complete conversion, and electron-withdrawing substituents at these positions seem to prevent the reaction.The auxiliary was removed by using titanium(IV) isopropoxide in benzyl alcohol followed by alkaline hydrolysis of the intermediate ester. the potent 5-HT1A receptor agonist (1R,2S)-2-(2-hydroxyphenyl)-N,N-dipropylcyclopropylamine 13 was synthesized by this method
- Vallaerda, Jerk,Appelberg, Ulf,Csoeregh, Ingeborg,Hacksell, Uli
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p. 461 - 470
(2007/10/02)
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- Stepwise mechanisms in the ene reaction of α,β-unsaturated esters with N-phenyl-l,2,4-triazoline-3,5-dione and Singlet oxygen. Intermolecular primary and secondary hydrogen isotope effects
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Intermolecular primary and secondary isotope effects on the ene reaction of N-phenyl-l,2,4-triazoline-3,5-dione (PTAD) and singlet oxygen (1O2) with deuterium-substituted (E)-2-methylbuten-2-oic (tiglic) acid methyl esters have been determined. In the case of 1O2, the primary isotope effect is 1.30-1.49 and the α and β secondary isotope effects are near unity, consistent with a stepwise reaction path via a perepoxide intermediate, where the allylic hydrogen-abstraction step is rate determining. On the other hand, the existence of both primary (1.44) and inverse α and β secondary isotope effects (0.91 and 0.77, respectively) in the PTAD reaction is consistent with either a concerted or a stepwise mechanism. Experiments in which both intermolecular primary and secondary isotope effects were measured at the same time suggest that, like singlet oxygen, PTAD reacts in a stepwise manner with the formation of the aziridinium imide interme diate (AI) in the rate-determining-step.
- Elemes, Yiannis,Foote, Christopher S.
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p. 6044 - 6050
(2007/10/02)
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- A facile conversion of (Z)-2-alkenoic esters into the (E)-isomers with diphenyl disulfide
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Diphenyl disulfide is shown to be an efficient catalyst for the isomerization of (Z)-2-alkenoic esters to (E)-2-alkenoic esters in boiling tetrahydrofuran.
- Miyata,Shinada,Ninomiya,Naito
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p. 1123 - 1125
(2007/10/02)
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- Regioselective Reaction of Singlet Oxygen with α,β-Unsaturated Esters
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The reaction of singlet oxygen with α,β-unsaturated esters shows a general preference for hydrogen abstraction on the alkyl group geminal to the ester.
- Orfanopoulos, Michael,Foote, Christopher S.
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p. 5991 - 5994
(2007/10/02)
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- NICKEL(0)-INDUZIERTE C-C-VERKNUEPFUNG ZWISCHEN 1,2-DIENEN UND KOHLENDIOXID
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1,2-Dienes react with CO2 at nickel(0) under the influence of basic chelate ligands to form nickela carboxylates.The structures of these five-membered complexes have been determined by spectroscopic and chemical methods.The regioselectivity of the C-C bond formation is discussed.
- Hoberg, H.,Oster, B. W.
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p. 321 - 326
(2007/10/02)
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- Polarized Ketene Dithioacetals. 28. A New General Highly Stereoselective and Regiospecific Method for Homologation of Ketones to α,β-Unsaturated Esters via α-Oxoketene Dithioacetals
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A new highly stereoselective and regiospecific general method for the conversion of active methylene ketones to α,β-unsaturated O-methyl esters, S-methyl esters, and aldehydes via the corresponding oxoketene dithioacetals has been developed.Thus the carbinols 7a-g obtained by sodium borohydride reduction of the corresponding oxoketene dithioacetals 6a-g, derived from acetophenones and their higher homologues, have been shown to undergo boron trifluoride etherate assisted methanolysis to give the corresponding (E)-methylcinnamates 3a-d and their α-alkyl derivatives 3e-g in high yields.Also the acetals 6h-k derived from alkylmethyl ketones gave the corresponding (E)-methylcrotonates 3h-k.Similarly, the acetals 6l-p derived from alicyclic ketones gave the corresponding cyclic ene esters 3l-p under identical conditions.A few carbinols, 7a-d, were shown to undergo partial hydrolysis in the presence of boron trifluoride etherate/water to give the corresponding S-methyl thiocinnamates 8a-d.The cyclic acetals 6l-n were also similarly converted to the corresponding cyclic S-methylene thio esters 8e-g.The (methylthio)alkenyl ketones 20a-d and 18 after borohydride reduction and acidic hydrolysis gave the corresponding (E)-α,β-unsaturated aldehydes 22a-d and 19.The mechanism governing these transformations has been proposed.
- Myrboh, Bekington,Ila, Hiriyakkanavar,Junjappa, Hiriyakkanavar
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p. 5327 - 5332
(2007/10/02)
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- FOUR ALIPHATIC ESTERS OF CHAMAEMELUM FUSCATUM ESSENTIAL OILY
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Four new aliphatic esters were isolated from the essential oil of Chamaemelum fuscatum.Three are esters of methacrylicacid with 2-methyl-2E-butenol, 2-hydroxy-2-methyl-3-butenol and 2-hydroxy-2-methyl-3-oxobutanol.The other is neryl isovalerate obtained in addition to known compounds.The structures were determined by spectral measurements and by synthesis.Key Word Index-Chamaemelum fuscatum; Compositae; essential oil; aliphatic esters.
- Pascual-T., J. De,Caballero, E.,Caballero, C.,Anaya, J.,Gonzalez, M. S.
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p. 1757 - 1760
(2007/10/02)
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- Cyclopropanation of α,β-Unsaturated Carbonyl Compounds and Nitriles with Diazo Compounds. The nature of the Involvement of Transition-Metal Promoters
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In the presence of molybdenum hexacarbonyl or molybdenum(II) acetate, ethyl diazoacetate and α-diazoacetophenone react with α,β-unsaturated carbonyl compounds and nitriles to form derivative cyclopropane and vinyl CH insertion products.In the absence of these promoters or in the presence of catalytic amounts of pyridine, 2-pyrazolines are the major or sole reaction products.Kinetic investigations for reactions between ethyl diazoacetate and α,β-unsaturated esters and nitriles in the presence of Mo(CO)6, Mo2(OAc)4, or pyridine demonstrate the absence of any significant influence by these molybdenum promoters or pyridine on the rates and activation parameters for ethyl diazoacetate decomposition.Representative 1-pyrazolines have been synthesized and observed to undergo dinitrogen extrusion without apparent influence by molybdenum promoters.The composite results suggest that these molybdenum promoted reactions occur by dipolar cycloaddition of diazocarbonyl compounds to α,β-unsaturated systems and that the derivative 1-pyrazoline intermediates undergo dinitrogen extrusion to form the observed cyclopropane and vinyl CH insertion products.Molybdenum promoters function to inhibit competitive tautomerization of the initially formed cycloaddition products.The relative effectiveness of a broad selection of transition-metal compounds in directing reactions between ethyl diazoacetate and α,β-unsaturated esters and nitriles to cyclopropane products is described.The cycloaddition / dinitrogen extrusion pathway is presented as a viable mechanism for cyclopropanation of α,β-unsaturated systems by diazo compounds, even for reactions performed in the presence of traditional cyclopropanation catalysts.
- Doyle, Michael P.,Dorow, Roberta L.,Tamblyn, William H.
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p. 4059 - 4068
(2007/10/02)
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- ADDITION OF CHLORINE, BROMINE AND BROMINE CHLORIDE TO SOME α,β-UNSATURATED METHYL ESTERS
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The additions of chlorine, bromine and bromine chloride to trans methyl 2-butenoate 1, trans methyl 2-methyl-2-butenoate 2 and methyl 3-methyl-2-butenoate 3 under ionic conditions were studied.Bromine chloride addition always gave as a major regioisomer the 2-bromo-3-chloro compound, almost quantitatively in the case of 3.The mechanism of bromonium ion ring-opening (SN1 or SN2) is discussed with respect to the double bond substitution and regioisomer proportions.The dihalo products were identified by MS, 1H and 13C NMR.
- Korhonen, Ilpo O. O.,Pitkaenen, Maija,Korvola, Jorma N. J.
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p. 2837 - 2841
(2007/10/02)
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- 13C-NMR. Spectral Differences between Corresponding Methyl Esters, Phenyl Esters and 2-Substituted Chromones
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The 13C-NMR. spectra of 2-substituted chromones (3) are compared with the data of the analogous methyl and phenyl esters (1 and 2).The chemical shift differences found are most prominent for the C-atoms in β-position to the ester carbonyl and chromone C(2), respectively.These shift differences are discussed in terms of conformational differences between the esters 1 and 2 and the analogous chromones 3.
- Sequin, Urs
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p. 2654 - 2664
(2007/10/02)
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- Preparation of organic acids and/or esters
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Carboxylic acids and/or esters are prepared by converting the STR1 moiety in a 1-substituted 2,2-trihaloethanol, or derivative wherein X represents halogen and R is hydrogen or an acyl group to an organic acid and/or ester grouping of the formula STR2 wherein R' is hydrogen or alkyl of 1 to 6 carbon atoms, in the process which comprises reacting the 1-substituted 2,2,2-trihaloethanol or acylated derivative with molecular oxygen in the presence of a catalyst comprising a complex of a transition metal having an atomic number from 21-30, 39-48 or 57-80 and at least one molecule of a ligand containing trivalent nitrogen, phosphorus, arsenic or antimony. This reaction is carried out in a reaction medium comprising an alcohol or aqueous alcohol having 1 to 6 carbon atoms optionally containing an alkali metal, said alcoholic solvent also serving as a reactant source when carboxylic acid esters are formed.
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- Synthesis of isoprenoid 1,5-dienes
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Aliphatic acids containing an isoprenoid 1,5-diene moiety are prepared in high yields by the selective gamma alkylation of α,β-unsaturated acids with allylic electrophiles. The gamma-regioselectivity of the alkylation is controlled by the use of the dicopper(I) dienolates prepared from the α,β-unsaturated acids. The method offers a particularly facile means for synthesizing isoprenoid 1,5-diene natural products such as farnesoic acid by alkylation of senecioic acid with geranyl bromide; geranoic acid by alkylation of senecioic acid with 3,3-dimethallyl bromide; and dl-lanceol by alkylation of tiglic acid with an allylic bromide derived from dl-limonene. Such products find use in the synthesis of insect pheremones, insect juvenile hormones, and components of perfumes.
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