- Polymethylene-Based Eight-Shaped Cyclic Block Copolymers
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A new strategy was developed for the synthesis of well-defined eight-shaped polymethylene (PM, equivalent to polyethylene)-based cyclic block copolymers, [c-(PM-b-PCL)]2, according to the following four steps: (a) synthesis of a B-thexyl-boracyclic initiator by cyclic hydroboration of 1,4-pentadiene-3-yl 2,2,5-trimethyl-1,3-dioxane-5-carboxylate with thexylborane; (b) polyhomologation of dimethylsulfoxonium methylide using this boracyclic initiator to afford α,ω-dihydroxyl linear PM (PM-OH)2; (c) synthesis of 4-miktoarm star block copolymers, (PM-alkyne)2-(PCL-N3)2, by esterification, deprotection, and ring-opening polymerization (ROP); and (d) intramolecular cyclization of (PM-alkyne)2-(PCL-N3)2, under high-dilution condition by copper-catalyzed "click" chemistry. All intermediates and final products were characterized by high-temperature gel permeation chromatography, proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and differential scanning calorimetry. Initial studies on the thermal and self-assembly behavior of the cyclic block copolymers and their corresponding precursors revealed a significant influence of the cyclic structure on the properties.
- Hadjichristidis, Nikos,Jiang, Yu
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- Synthesis of Well-Defined Polyethylene-Based 3-Miktoarm Star Copolymers and Terpolymers
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Novel polyethylene (PE)-based 3-miktoarm star copolymers A2B, (AB)2B and terpolymers (AC)2(BC) [A: PE; B, C: polystyrene (PS) or poly(methyl methacrylate) (PMMA)] were synthesized by combining boron chemistry, polyhomologation, and atom transfer radical polymerization (ATRP). 1,4-Pentadiene-3-yl 2-bromo-2-methylpropanoate was first synthesized followed by hydroboration with thexylborane to afford B-thexylboracyclanes, a multi-heterofunctional initiator with two initiating sites for polyhomologation and one for ATRP. After polyhomologation of dimethylsulfoxonium methylide the α,ω-dihydroxyl polyethylene (PE-OH)2-Br produced served as macroinitiator for the ATRP of styrene to afford (PE-OH)2-(PS-Br). Both (PE-OH)2-Br and (PE-OH)2-(PS-Br) were transformed to two new trifunctional macroinitiators (PE-Br)2-Br and (PE-Br)2-(PS-Br) through esterification reactions and used for the synthesis of (AB)2B and (AC)2(BC) 3-miktoarm star co/terpolymers. All intermediates and final products were characterized by 1H NMR, high temperature gel permeation chromatography (HT-GPC), and differential scanning calorimetry (DSC). The synthetic method is a general one and can be used for the synthesis of complex PE-based architectures by combination with other living/living-controlled polymerization techniques.
- Zhang, Zhen,Altaher, Maryam,Zhang, Hefeng,Wang, De,Hadjichristidis, Nikos
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- Total synthesis of (±)-kalihinol C
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The total synthesis of kalihinol C, a bis-isonitrile marine diterpenoid isolated from Acanthella sp., is reported. The decalin framework was established via an intramolecular Diels-Alder cycloaddition and subsequently functionalized through a series of substrate-controlled diastereoselective transformations to install the tertiary isonitrile, β-hydroxy isonitrile, and pendant tetrahydrofuranyl ring.
- White, Ryan D.,Keaney, Gregg F.,Slown, Corin D.,Wood, John L.
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- Divinylcarbinol Desymmetrization Strategy: A Concise and Reliable Approach to Chiral Hydroxylated Fatty Acid Derivatives
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By the aid of the catalytic desymmetrization of divinylcarbinol as one-pot asymmetric induction and protection of olefin, asymmetric total syntheses of two chiral hydroxylated fatty acid derivatives were successfully achieved. The desired stereoisomers could be concisely prepared in mild conditions in a highly convergent manner. Thus, this novel strategy can help stereochemical elucidations of natural products, which have difficulties in spectroscopic stereochemical analyses due to their local symmetries in the vicinities of the stereogenic secondary hydroxyl units.
- Sugimoto, Kenji,Kobayashi, Ami,Kohyama, Aki,Sakai, Haruka,Matsuya, Yuji
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p. 3970 - 3980
(2021/03/01)
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- Construction of Silicon-Containing Seven-Membered Rings by Catalytic [4 + 2 + 1] Cycloaddition through Rhodium Silylenoid
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A rhodium-catalyzed [4 + 2 + 1] cycloaddition involving 1,3-diene, alkyne, and silylene to afford silicon-containing seven-membered rings was established. In the presence of a rhodium catalyst bearing bis(diphenylphosphino)methane (DPPM), nona-1,3-dien-8-yne derivatives reacted efficiently at 80-110 °C with boryl(isopropoxy)silane or boryl(diethyamino)silane, which reacts as the synthetic equivalent of silylene, to afford 1-silacyclohepta-2,5-dienes (2,5-dihydro-1H-silepines). Regiodivergent and chemo- and stereoselective functionalization of the seven-membered nonconjugated diene was achieved by hydroboration mediated by Cs2CO3 or an iridium catalyst.
- Sasaki, Ikuo,Ohmura, Toshimichi,Suginome, Michinori
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supporting information
p. 2961 - 2966
(2020/04/10)
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- Olefin-Migrative Cleavage of Cyclopropane Rings through the Nickel-Catalyzed Hydrocyanation of Allenes and Alkenes
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A nickel-catalyzed hydrocyanation triggered by hydronickelation of the carbon-carbon double bonds of allenes followed by cyclopropane cleavage is described. The observed regio- and stereochemistries in the products are strongly influenced by the initial hydronickelation step, and allenyl- and methylenecyclopropanes reacted smoothly to promote the cleavage of cyclopropane. In contrast, this cleavage was not observed with vinylidenecyclopropanes, because the initial hydronickelation does not give a suitable intermediate for cleavage of the cyclopropanes. (Figure presented.).
- Hori, Hiroto,Arai, Shigeru,Nishida, Atsushi
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supporting information
p. 1170 - 1176
(2017/04/13)
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- F- Nucleophilic-Addition-Induced Allylic Alkylation
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Herein we present a novel strategy based on palladium-catalyzed allylic alkylation by taking advantage of the nucleophilic addition of external fluoride onto gem-difluoroalkenes as the initiation step. The merit of this protocol is highly appealing, as it enables a formal allylation of trifluoroethylarene derivatives through the in situ generation of β-trifluorocarbanions, which otherwise are deemed to be problematic in deprotonative allylation. Furthermore, this strategy distinguishes itself by high modularity, operational simplicity, and wide substrate scope with respect to allyl carbonates, giving rise to a broad array of homoallyltrifluoromethane derivatives, which otherwise would not be easily obtained using existing synthetic methods.
- Tian, Panpan,Wang, Cheng-Qiang,Cai, Sai-Hu,Song, Shengjin,Ye, Lu,Feng, Chao,Loh, Teck-Peng
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supporting information
p. 15869 - 15872
(2016/12/23)
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- A Cu/Pd Cooperative Catalysis for Enantioselective Allylboration of Alkenes
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A cooperative Cu/Pd-catalyzed asymmetric three-component reaction of styrenes, B2(pin)2, and allyl carbonates was reported. This reaction, in the presence of chiral CuOAc/SOP and achiral Pd(dppf)Cl2 catalysts, occurs smoothly with high enantioselectivities (up to 97% ee). The allylboration products, which contain alkene (or diene) unite and alkylboron group, are easily functionalized. The utility of this protocol was demonstrated through the synthesis of an antipsychotic drug, ()-preclamol.
- Jia, Tao,Cao, Peng,Wang, Bing,Lou, Yazhou,Yin, Xuemei,Wang, Min,Liao, Jian
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supporting information
p. 13760 - 13763
(2016/01/15)
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- Enantioselective total synthesis of pladienolide B: A potent spliceosome inhibitor
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An enantioselective and convergent total synthesis of pladienolide B (1) is described. Pladienolide B binds to the SF3b complex of a spliceosome and inhibits mRNA splicing activity. The synthesis features an epoxide opening reaction, an asymmetric reduction of a β-keto ester, and a cross metathesis strategy for the side chain synthesis.
- Ghosh, Arun K.,Anderson, David D.
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supporting information
p. 4730 - 4733
(2013/01/15)
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- 6,8,10-UNDECATRIEN-(3 OR 4)-ONE AND PERFUME COMPOSITION
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This invention offers 6,8,10-undecatrien-3-one or 6,8,10-undecatrien-4-one which are represented by the following formula (1) [in the formula, either one of A and B stands for carbonyl group and the other stands for methylene group, and the wavy line signifies cis-form, trans-form, or a mixture of cis- and trans-form at an optional ratio] and which can reproduce an odor rich in naturality and freshness.
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Page/Page column 9-10
(2010/04/25)
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- 6,8,10-UNDECATRIEN-3-OL OR 6,8,10- UNDECATRIEN-4-OL, AND PERFUME COMPOSITION
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This invention offers 6,8,10-undecatrien-3-ol and 6,8,10-undecatrien-4-ol. These compounds possess not only woody green note, but also fruity note rich in naturality and freshness, and aroma compositions blended therewith are useful for imparting fragrance and flavor to food and beverage, perfumed cosmetics, medicaments and the like.
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Page/Page column 9
(2010/04/25)
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- Stereoselectivity in the rhodium-catalysed reductions of nonconjugated dienes
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The stereochemical course of rhodium-catalysed addition of hydrogen and catecholborane to bicyclo[2.2.1]heptadiene, and of hydrogen to a range of cyclic dienes has been analysed. For hydroboration, the overall catalytic reaction possesses exo-selectivity, but the initial step is endo-selective. For hydrogenation (deuteration), the first step may occur with either exo- or endo- selectivity, depending on the structure of the diene. This enables a distinction to be made between pathways involving prior dissociation of the diene, and direct addition to the complexed diene without full dissociation. The relative ease of hydrogenation of the first and second doublebonds varies markedly with reactant structure, and also depends on the choice of catalyst ligands. For dicyclopentadiene, hydrogenation of the cyclopentene double bond is accompanied by rapid alkene isomerisation, as revealed by deuterium addition. The asymmetric hydrogenation of acyclic skipped mesodienes is reported, demonstrating control of relative rates of the two sequential steps, with ees of up to 53% after the first reduction.
- Nguyen, Bao,Brown, John M.
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supporting information; experimental part
p. 1333 - 1343
(2009/12/27)
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- A novel, chemoselective and efficient microwave-assisted deprotection of silyl ethers with Selectfluor
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A novel microwave-assisted, chemoselective and efficient method for the cleavage of silyl ethers (aliphatic and aromatic) catalyzed by Selectfluor is reported. A wide range of TBS-, TIPS-, and TBDPS-protected alkyl silyl ethers can be chemoselectively cleaved in high yield in the presence of aryl silyl ethers. The chemoselective deprotection of phenolic TBS ethers, and not the TIPS- or TBDPS-protected phenolic ethers, and the deprotection of silyl esters were also achieved under these reaction conditions. In addition, the transetherification and etherification of benzylic hydroxy groups in alcoholic solvents is observed.
- Shah, Syed Tasadaque A.,Singh, Surendra,Guiry, Patrick J.
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experimental part
p. 2179 - 2182
(2009/07/01)
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- The chemoselective and efficient deprotection of silyl ethers using trimethylsilyl bromide
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An efficient and chemoselective cleavage of silyl ethers (primary, secondary and aromatic) by using catalytic quantities of trimethylsilyl bromide (TMSBr) in methanol is reported. A wide range of alkyl silyl ethers such as TBS, TIPS, and TBDPS can be chemoselectively cleaved in high yield in the presence of aryl silyl ethers. The deprotection of silyl esters was also achieved employing catalytic quantities of TMSBr. The Royal Society of Chemistry 2008.
- Shah, Syed Tasadaque A.,Guiry, Patrick J.
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experimental part
p. 2168 - 2172
(2009/02/01)
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- Thioreductones and derivatives
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Replacement of one or two (principally also three) O-atoms in aci-reductones by sulfur leads to the corresponding thioreductones. In the present paper, different methods of their synthesis are discussed. Substitution of the bromo nucleofug in the 2-position of 1,3-dicarbonyl compounds as well as of a 3-oxosulfone by selected sulfur nucleophiles is assumed to follow an 5 RN1 pathway. Characteristic properties, some typical reactions, and selected derivatives were studied. 5-Alkyl- and 5-aryl-substituted cyclic 2-thioreductones have been found to be synthons for the preparation of vinylogous reductones (2,3-diacyl-1,4-dihydroxy-1,3-dienes) and of tetraacyl ethylenes as their bis-dehydro products.
- Schank, Kurt,Buegler, Stephan,Folz, Harald,Schott, Norbert
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p. 1606 - 1649
(2008/02/09)
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- Cation radical cycloaddition polymerization: Diels-Alder copolymerization
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The Diels-Alder cycloaddition copolymerization of a bis(diene) with ionizable bis(dienophiles) via a cation radical mechanism has been accomplished using tris(4-bromophenyl)aminium hexachloroantimonate as a catalyst in dichloromethane solvent. The reactions occur at 0°C and yield Diels-Alder polymers of Mw up to ca. 10,000 and a polydispersity index ca. 2.
- Bauld, Nathan L.,Aplin, J. Todd,Yueh, Wang,Endo, Stephanie
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p. 825 - 830
(2007/10/03)
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- Novel Conversion of Epoxides to One Carbon Homologated Allylic Alcohols by Dimethylsulfonium Methylide
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The reaction of excess of dimethylsulfonium methylide with terminal, allylic, or benzylic epoxides affords good to excellent yields of one carbon homologated allylic alcohols.
- Alcaraz, L.,Harnett, J. J.,Mioskowski, C.,Martel, J. P.,Gall, T. Le,et al.
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p. 5449 - 5452
(2007/10/02)
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- Example of thermodynamic control in palladium-catalyzed allylic alkylation. evidence for palladium-assisted allylic C-C bond cleavage
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Pd(0)-catalyzed reactions of a number of dienyl acetates with dialkyl malonates show that the regiochemistry of the reaction is very dependent on the reaction conditions. At low temperature and short reaction times the reaction is under kinetic control, but at elevated temperature and longer reaction times the reaction is under thermodynamic control. Under the latter conditions it was demonstrated that the kinetic allylic malonate rearranged to its thermodynamically more stable regioisomer in the presence of the Pd(0) catalyst. The results strongly support the cleavage of an allylic C-C bond by Pd(0), and thus the dialkyl malonate anion has acted as a leaving group.
- Nilsson, Ylva I.M.,Andersson, Pher G.,B?ckvall, Jan-E.
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p. 6609 - 6613
(2007/10/02)
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- N-ACYLAMINO ACID DERIVATIVES AND THEIR PHARMACEUTICAL COMPOSITIONS
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An N-acylamino acid derivative of the formula: STR1 wherein the substituents are herein defined or a salt thereof, which is useful as hypotensive drugs.
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- An Efficient Synthesis of Functionalized Tricyclo1.6>dodec-4-enes by a Stereoselective Intramolecular Diels-Alder Reaction
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An efficient and highly stereoselective synthesis of functionalized tricyclo1.6>dodec-4-enes (1c,e,f-h), which would be useful and common synthons for constructing basic carbon frameworks of various kinds of natural products, is described.The key feature of the synthesis was a stereoselective intramolecular Diels-Alder reaction of the cyclohexanone derivatives (10c,e,f-h), which were easly derived from cyclohexanone in 4-5 steps.The whole structure and the stereochemistry of a major cycloadduct (1e) was established by a single-crystal X-ray analysis.
- Shishido, Kozo,Hiroya, Kou,Ueno, Yutaka,Fukumoto, Keiichiro,Kametani, Tetsuji,Honda, Toshio
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p. 829 - 836
(2007/10/02)
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- Lewis Acid Mediated Claisen-Type Rearrangement of Aryl Dienyl Ethers
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Rearrangement of aryl pentadienyl ethers in the presence of BF3*OEt2 affords pentadienyl phenols in good yields without formation of the corresponding rearranged products.The mechanism of this rearrangement was studied by deuterium labeling and cross-coupling reactions.The scope and limitations of the rearrangement are discussed.
- Maruyama, Kazuhiro,Nagai, Naoshi,Naruta, Yoshinori
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p. 5083 - 5092
(2007/10/02)
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- Cyclopentene Annulation via Intramolecular Addition of Diazo Ketones to 1,3-Dienes. Applications to the Synthesis of Cyclopentanoid Terpenes
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Initial model studies investigating the utility of a new intramolecular cyclopentene annulation procedure are described as pertaining to the preparation of bicyclooctenones.Several 1-diazo-5,7-octadien-2-ones substituted at the 1-, 7-, or 8-position were decomposed in the presence of Cu(acac)2 to yield stereospecifically the corresponding vinylcyclopropanes 13, 16, 21, 24, and 27.The thermal as well as the rhodium-promoted modes of rearrangement to the appropriate cyclopentenes 14, 17, 22a,b, and 28a,b were studied.Where necessary, diastereomers were separatedand structurally assigned by relying on 13C NMR spectroscopy. 13C NMR data are provided for all new compounds in the bicyclooctane series to serve as an aid in assignments of cyclopentanoid terpenes synthesized by this methodology.The intramolecular cylopropanation-rearrangement sequence of dienic diazo ketones has been shown to provide facile access to bicyclooctanes of the type 14, 17, 22a,b, and 25a,b which are of value as terpene synthons.Enhanced stereoselectivity was observed in the rhodium-promoted cyclopentene rearrangements in favor of the less concave diastereomers (22a, 25a, and 28a).Finally, the sesquiterpene hirsutene (31) was synthesized in 37percent overall yield by this methodology. 13C NMR data for several tricyclo2,6>undecane compounds are also provided.
- Hudlicky, Tomas,Koszyk, Francis J.,Kutchan, Toni M.,Sheth, Jagdish P.
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p. 5020 - 5027
(2007/10/02)
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- Process for the preparation of poly-unsaturated hydrocarbons
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Process for the preparation of poly-unsaturated hydrocarbons, in particular undeca-1,3,5-triene, which comprises reacting a quaternary phosphonium salt with hexanal. The product obtained in accordance with the process of the invention is a useful perfuming ingredient.
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