- Heavier Carbonyl Olefination: The Sila-Wittig Reaction
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The Wittig reaction is one of the most versatile tools in the repertoire of organic chemists. Thus, a broad variety of carbonyl compounds can be converted to tailor-made alkenes with phosphorus ylides under mild conditions. However, no comparable reaction has been reported for silanones, the silicon congeners of ketones. Here, we demonstrate for the first time the successful application of the Wittig olefination to iminosilylsilanone 1. The selective formation of a series of silenes (R2Sia? CR2) via the sila-Wittig reaction revealed an unprecedented approach to otherwise elusive compounds. In addition, the highly reactive and zwitterionic nature of 1 was also susceptible to nucleophilic attacks and cycloaddition reactions by and with the phosphorus ylides. Our results therefore make another important contribution to discovering the differences and similarities between carbon and silicon.
- Reiter, Dominik,Frisch, Philipp,Szilvási, Tibor,Inoue, Shigeyoshi
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p. 16991 - 16996
(2019/10/16)
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- Catalyst-Enabled Site-Divergent Stereoselective Michael Reactions: Overriding Intrinsic Reactivity of Enynyl Carbonyl Acceptors
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A site-divergent stereoselective Michael reaction system is developed based on the identification of two distinct catalysts. Cinchonidine-derived thiourea catalyzes the 1,4-addition of prochiral azlactone enolates to enynyl N-acyl pyrazoles in a highly diastereo- and enantioselective manner to give stereochemically defined alkynes, while P-spiro chiral triaminoiminophosphorane catalytically controls the stereoselective 1,6-addition and the consecutive γ-protonation of the vinylogous enolate intermediate to afford Z,E-configured conjugated dienes. This 1,6-adduct serves as a valuable precursor for the synthesis of a 2-amino-2-deoxy sugar.
- Uraguchi, Daisuke,Shibazaki, Ryo,Tanaka, Naoya,Yamada, Kohei,Yoshioka, Ken,Ooi, Takashi
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supporting information
p. 4732 - 4736
(2018/04/23)
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- New reactions and reactive intermediates in the pyrolysis of cyclic phosphonium ylides
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Pyrolysis, either neat or in diphenyl ether solution, results in the conversion of both 4-triphenylphosphoranylidenetetrahydrofuran-2,3,5-trione and 4-triphenylphosphoranylidenetetrahydrothio-phene-2,3,5-trione into 3,5-bis(triphenylphosphoranylidene)cyclopentane-1,2,4-trione. These reactions involve extrusion of CO2 or COS to give 3-triphenylphosphoranylidenecyclopropane-1,2-dione which further loses CO to give triphenylphosphoranylideneketene. The precise way in which these two reactive phosphorus compounds combine to give the observed product has been examined by chemical and isotopic labelling studies. Cyclotrimerization of triphenylphosphoranylideneketene upon thermolysis in diphenyl ether has also been observed for the first time. The erroneous literature interpretation of the 13C NMR spectrum for triphenylphosphoranylideneketene is corrected.
- Aitken, R. Alan,Bj?rnstad, Vidar,Massil, Tracy,Skramstad, Jan,Young, Robert J.
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p. 293 - 301
(2017/10/27)
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- A cell-permeable and triazole-forming fluorescent probe for glycoconjugate imaging in live cells
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A new fluorescence-forming probe, coumOCT, designed by fusing cyclooctyne with a coumarin fluorophore was successfully used for the imaging of azido-glycoconjugates in living HeLa cells. This probe is cell-permeable and generates fluorescence after triazole formation, thus minimizing the background signal and enabling the real-time intracellular imaging of glycoconjugate trafficking.
- Shie, Jiun-Jie,Liu, Ying-Chih,Hsiao, Jye-Chian,Fang, Jim-Min,Wong, Chi-Huey
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supporting information
p. 1490 - 1493
(2017/02/05)
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- Ravynic acid, an antibiotic polyeneyne tetramic acid from: Penicillium sp. elucidated through synthesis
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A new antibiotic natural product, ravynic acid, has been isolated from a Penicillium sp. of fungus, collected from Ravensbourne National Park. The 3-acylpolyenyne tetramic acid structure was definitively elucidated via synthesis. Highlights of the synthetic method include the heat induced formation of the 3-acylphosphorane tetramic acid and a selective Wittig cross-coupling to efficiently prepare the natural compounds carbon skeleton. The natural compound was shown to inhibit the growth of Staphylococcus aureus down to concentrations of 2.5 g mL-1.
- Myrtle,Beekman,Barrow
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p. 8253 - 8260
(2016/09/09)
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- REACTIVE LABELLING COMPOUNDS AND USES THEREOF
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Provided are azido-BODIPY compounds of formula (I), cyclooctyne-based fluorogenic probes of formula (IV), and activity-based probes of formula (VI). These compounds undergo azide alkyne cycloadditions (AAC) with to form triazolyl products. The provided compounds are useful for detection and imaging of alkyne-, or azide-containing molecules. Methods for detection and imaging biomolecules using compounds of the present disclosure are disclosed.
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- REACTIVE LABELLING COMPOUNDS AND USES THEREOF
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Provided are azido-BODIPY compounds of formula (I), cyclooctyne-based fluorogenic probes of formula (IV), and activity-based probes of formula (VI). These compounds undergo azide-alkyne cycloadditions (AAC) with to form triazolyl products. The provided compounds are useful for detection and imaging of alkyne-, or azide-containing molecules. Methods for detection and imaging biomolecules using compounds of the present disclosure are disclosed.
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Paragraph 00206; 00207
(2015/12/08)
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- Semisynthesis of (+)-angeloyl-gutierrezianolic acid methyl ester diterpenoid
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This paper describes the use of zamoranic acid in the first semisynthesis of the furolabdane (+)-angeloyl-gutierrezianolic acid methyl ester diterpenoid, which also establishes the absolute configuration of the natural product. Direct deconjugation of Δs
- Marcos,Benéitez,Moro,Basabe,Díez,Urones
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experimental part
p. 8605 - 8614
(2011/01/04)
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- Toward the development of a general chiral auxiliary. Enantioselective alkylation and a new catalytic asymmetric addition of silyloxyfurans: Application to a total synthesis of (-)-rasfonin
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An enantioselective total synthesis of the apoptosis-inducing natural product, (-)-rasfonin, is described. Camphor lactam-mediated asymmetric alkylation reactions enabled the installation of three stereogenic centers with >95:5 diastereoselectivity. A modified Corey-Peterson olefination was employed in the construction of the (E,E)-diene system. A highly diastereoselective, asymmetric vinylogous Mukaiyama aldol addition was conducted using a chiral cationic oxazaborolidine catalyst. The pyranone core of the natural product was prepared via a DBU-promoted rearrangement of a furanol to its corresponding pyranol with concomitant [1,4]-silyl transfer. Copyright
- Boeckman Jr., Robert K.,Pero, Joseph E.,Boehmler, Debra J.
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p. 11032 - 11033
(2007/10/03)
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- Synthesis of ent-halimanolides from ent-halimic acid
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Three natural ent-halimanolides have been synthesized from ent-halimic acid. Their structures have been confirmed as well as their absolute configurations established. Bestmann methodology has been used for the synthesis of butenolides and for the synthes
- Marcos,Pedrero,Sexmero,Diez,Garcia,Escola,Basabe,Conde,Moro,Urones
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p. 3301 - 3310
(2007/10/03)
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- Synthesis of Microcolin B, a Potent New Immunosuppressant Using an Efficient Mixed Imide Formation Reaction
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Microcolin B, a potent new immunosuppressant isolated from blue-green alga Lyngbya majuscula off the Venezuelan coast, has been made using a methyl-directed asymmetric hydrogenation reaction with rhodium on alumina catalyst on lactone 4 for the synthesis of the key (R,R)-2,4-dimethyl-octanoic acid fragment 1. A new, direct mixed imide formation reaction was also developed for the production of the unusual prolylpyrrolen-2-one 2 portion of microcolin. The pentafluorophenyl ester of CBZ-proline 5 was reacted with the lithium imidate of lactam 6, providing the mixed imide in 80% yield. Coupling of acid 1 with the N-terminus of the tripeptide, followed by coupling with pyrrolylproline 2, gave microcolin B. The new mixed-imide forming reaction was also applied to a formal total synthesis of microcolin A. The pentafluorophenyl ester of TBS-protected cis-hydroxyproline was coupled with lactam 6, and the resultant imide was converted to the key pyrrolylproline made previously for microcolin A.
- Andrus, Merritt B.,Li, Wenke,Keyes, Robert F.
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p. 5542 - 5549
(2007/10/03)
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- Phosphane Alkylenes, 52. - Reactions of triphenylphosphoranes with Carbon Dioxide
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2-(Triphenylphosphoranylidene) carboxylic acid esters 6 have been synthesized from 1-(trimethylsilylalkylidene)phophoranes 4 and carbon dioxide.The reactions of the ylides 6 with aldehydes 9 lead to α,β-unsaturated silyl esters 10 in good yields and with high (E) stereoselectivity.Thermolysis of 6d affords (oxovinylidene)triphenylphosphorane (7). Key Words: Phosphonium ylides / Wittig reaction
- Bestmann, Hans-Juergen,Dostalek, Roman,Zimmermann, Reiner
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p. 2081 - 2084
(2007/10/02)
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- Cumulated Ylides XIX. Chain-lenghthening Difunctionalization of Grignard Compounds by Reaction with Ketenylidenetriphenylphosphorane. A New Route to (E)-α,β-Unsaturated Ketones and the Queen Substance
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The reaction of Grignard compounds with ketenylidenetriphenylphosphorane and subsequent hydrolysis yields 2-oxoalkylidenetriphenylphosphoranes.The latter undergo Wittig reaction, whereby (E)-α,β-unsaturated ketones are obtained.An application of this strategy to the synthesis of carbonyl homologues of Lepidoptera pheromones and the queen substance is shown.
- Bestmann, Hans Juergen,Schmidt, Martin,Schobert, Rainer
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- Cumulated Ylides, VI: A New Synthesis of (Triphenylphosphoranylidene)keten, its Thio Analogue, and Stable Propadienylidenetriphenylphosphoranes
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Reaction of sodium bis(trimethylsilyl)amide (2) with (methoxycarbonylmethylene)triphenylphosphorane (1a) or its dithio analogue 1b leads to β-elimination and formation of (triphenylphosphoranylidene)ketene (3a) and -thioketene (3b), respectively.The analo
- Bestmann, Hans Juergen,Sandmeier, Dieter
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p. 274 - 277
(2007/10/02)
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