- A novel and convenient synthesis of 3-methylfuran-2(5H)-one
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3-Methylfuran-2(5H)-one (1a), a precursor of strigol and its analogues, is prepared in a highly efficient manner by a regiocontrolled alcoholysis of citraconic anhydride and subsequent reduction via the mixed anhydride 5c.
- Nefkens, Gerard H.L.,Thuring, Jan Willem J.F.,Zwanenburg, Binne
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- An efficient and short synthesis of 3-methyl-2(5H)-furanone, a synthon for strigol analogues
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A three steps synthesis of 3-methyl-2(5H)-furanone from citraconic anhydride is reported. The furanone is prepared in an overall yield of 60%.
- Mangnus,Zwanenburg
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- A New Synthesis of Substituted Butenolides via Cation-Initiated Ring Expansion/Elimination of β-Lactones
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When treated with silver ion, γ-bromo β-lactones, available via bromolactonization, undergo a ring expansion/elimination reaction to afford substituted butenolides.
- Black, T. Howard,Huang, Jianhua
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- Stereoselective Hydride Reduction of Tetronic Acid Derivatives. Synthesis of Branched-Chain Tetrofuranoses
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The 3-methoxymethyl derivatives of 2-methyl-D,L-threofuranose (10a) and 2-deoxy-2-methyl-D,L-erythrofuranose (11a) are prepared starting from 2-methyltetronic acid (1).The key step is the stereoselective reduction of the 3-oxo-function of 2-chloro-2-methyl-3-oxo-γ-butyrolacton (2) by sodiumborohydride, which proceeds predominantly anti with respect to the C, Cl-bond.The configuration of the reduction products has been established by 1H- and 13C-NMR.-spectroscopy.
- Wyss, Heinz,Voegeli, Ulrich,Scheffold, Rolf
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- A new expedient synthesis of 3-methyl-2(5 H)-furanone, the common substructure in strigolactones, and its proposed biosynthesis
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3-Methyl-2(5H)-furanone is the common structural unit in natural and several synthetic strigolactones, which are germination stimulants for seeds of the parasitic weeds Striga and Orobanche spp. A simple, one-step, ring-closing metathesis of allyl methacrylate using an appropriate Grubbs catalyst gives this furanone in good yield. Acid-catalyzed condensation of glyoxal and methylmalonic acid gives 5-hydroxy-3-methyl-2(5H)-furanone, which is another synthon for the introduction of the furanone unit into strigolactones. In addition, a biosynthetic pathway is presented for the incorporation of the furanone unit into strigolactones, which is relevant in view of the current interest in the newly discovered biological functions of strigolactones. Georg Thieme Verlag Stuttgart New York.
- Malik, Heetika,Rutjes, Floris P. J. T.,Zwanenburg, Binne
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- Butenolide synthesis from functionalized cyclopropenones
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A general method to synthesize substituted butenolides from hydroxymethylcyclopropenones is reported. Functionalized cyclopropenones undergo ring-opening reactions with catalytic amounts of phosphine, forming reactive ketene ylides. These intermediates can be trapped by pendant hydroxy groups to afford target butenolide scaffolds. The reaction proceeds efficiently in diverse solvents and with low catalyst loadings. Importantly, the cyclization is tolerant of a broad range of functional groups, yielding a variety of α- and γ-substituted butenolides.
- Nguyen, Sean S.,Ferreira, Andrew J.,Long, Zane G.,Heiss, Tyler K.,Dorn, Robert S.,Row, R. David,Prescher, Jennifer A.
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p. 8695 - 8699
(2019/10/28)
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- Comparative studies of palladium and copper-catalysed γ-arylation of silyloxy furans with diaryliodonium salts
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The γ-arylation of substituted silyl-activated butenolides has been studied using a broad scope of unsymmetrical hypervalent diaryliodonium salts via a palladium- or copper-catalysed coupling reaction, yielding interesting reactivity trends. The mild catalytic conditions and coupling partner variability provide access to synthetically useful building blocks toward the pursuit of aryl-lactone containing natural products and allows for facile diversification.
- Alexander, Taylor S.,Clay, Travis J.,Maldonado, Bryan,Nguyen, Johny M.,Martin, David B.C.
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p. 2229 - 2238
(2019/03/06)
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- Α-hydroxycarboxylic acid or its oligomer by treatment with hydrogen at high temperature and high pressure water or hydroxy butyrolactone derivative γ - furanone derivative
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PROBLEM TO BE SOLVED: To provide a method of manufacturing a furanone derivative or a γ-butyrolactone derivative by a high temperature high pressures water treatment of hydroxy carboxylic acid having a hydrogen atom and a hydroxyl group at α-position or its oligomer.SOLUTION: A method of manufacturing a furanone derivative or a γ-butyrolactone derivative uses hydroxy carboxylic acid having a hydrogen atom and a hydroxyl group at α-position or its oligomer as a raw material, and mixes the raw material solution and high temperature high pressure water, and conducts a reaction at a temperature in a range of 200°C to 500°C to synthesize the furanone derivative or the γ-butyrolactone derivative. A novel synthesis method of the furanone derivative or the γ-butyrolactone derivative using the hydroxy carboxylic acid having a hydrogen atom and a hydroxyl group at α-position or its oligomer as the raw material can be provided and it can synthesize with one step reaction, has high yield, and is easy to separate and purify.
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Paragraph 0027; 0055
(2017/11/11)
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- The bioinspired design of a reagent allows the functionalization of Cα-H of α,β-unsaturated carbonyl compounds via the Baylis-Hillman chemistry under ambient conditions
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A rationally designed reagent capable of affecting alkylation at Cα of α,β-unsaturated carbonyl compounds is reported. The reaction proceeded at room temperature without any additives. The pH and H-bond formation during the reaction play a key role in the working of the reagent.
- Singh, Palwinder,Kumar, Arun,Kaur, Sukhmeet,Kaur, Jagroop,Singh, Harpreet
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supporting information
p. 2936 - 2939
(2016/02/20)
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- Enzymatic synthesis of optically active lactones via asymmetric bioreduction using ene-reductases from the old yellow enzyme family
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In contrast to the widely studied asymmetric bioreduction of α,β-unsaturated carboxylic acid esters catalyzed by ene-reductases, the reaction applied to lactones remains unexplored. A broad set of ene-reductases was found to reduce various α-, β- and γ-substituted α,β-unsaturated butyrolactones to yield the corresponding saturated non-racemic lactones. Substitution patterns greatly influenced activities and stereoselectivities and lactone products were obtained in moderate to excellent yields; importantly, enzyme-based stereocontrol allowed access to both enantiomers in up to >99% ee. Chiral recognition of a distant γ-center led to kinetic resolution with remarkable enantioselectivities (E values up to 49). An unprecedented case of dynamic kinetic resolution was observed with 3-methyl-5-phenylfuran-2(5H)-one, whereby spontaneous racemization of the substrate furnished the product in up to 73% conversion and >99% ee and 96% de.
- Turrini, Nikolaus G.,Hall, Mélanie,Faber, Kurt
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p. 1861 - 1871
(2015/06/02)
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- Catalytic dehydration of d-xylose to 2-furfuraldehyde in the presence of Zr-(W,Al) mixed oxides. Tracing by-products using two-dimensional gas chromatography-time-of-flight mass spectrometry
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Zirconium-tungsten mixed oxides (ZrW) are effective catalysts in the aqueous-phase dehydration of d-xylose to 2-furfuraldehyde (Fur), at 170 °C. The texture and acid properties of ZrW materials were modified to enhance Fur yields. The catalysts prepared by co-condensation without a templating agent (ZrW(X), X = NO3, Cl; X is related to the type of zirconium precursor) possess relatively low specific surface area and amounts of accessible acid sites, leading to a modest Fur yield of ca. 35% at 99% conversion. The use of a templating agent in the preparation of mesoporous ZrW (ZrW-MP) increased considerably the specific surface area and the amount of accessible acid sites, which resulted in enhanced Fur yields (42%) reached at comparable conversions. Further improvements in Fur yields at high conversions were accomplished by introducing aluminium in the catalyst preparation procedure to give ZrAlW-MP (51% yield at 98% conversion). Fairly good catalytic results were also obtained in the case of the ZrAlW-MP catalyst, using solely water as solvent (46% yield at 93% conversion). A study of the identification of the reaction by-products by two-dimensional gas chromatography (GC × GC) combined with time-of-flight mass spectrometry (ToFMS) was carried out.
- Antunes, Margarida M.,Lima, Sérgio,Fernandes, Auguste,Candeias, Joana,Pillinger, Martyn,Rocha, Sílvia M.,Ribeiro, Maria Filipa,Valente, Anabela A.
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p. 127 - 135
(2013/01/15)
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- General, regiodefined access to α-substituted butenolides through metal-halogen exchange of 3-bromo-2-silyloxyfurans. Efficient synthesis of an anti-inflammatory Gorgonian lipid
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(Chemical Equation Presented) A variety of α-substituted butenolides were efficiently prepared from 3-bromo-2-triisopropylsilyloxyfuran via lithium-bromine exchange and in situ quench with carbon or heteroatom electrophiles. The inherent flexibility of this methodology is illustrated by a short and efficient synthesis of an anti-inflammatory marine natural product.
- Boukouvalas, John,Loach, Richard P.
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p. 8109 - 8112
(2008/12/22)
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- Cross metathesis of α-methylene lactones II: γ- and δ-lactones
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The cross metathesis reactivities of α-methylene-γ- butyrolactone and an α-methylene-δ-lactone have been investigated. α-Methylene-γ-butyrolactone undergoes rapid and efficient olefin isomerization in the presence of second-generation metathesis catalysts. However, cross metathesis can be achieved with the additive 2,6- dichlorobenzoquinone. In contrast, the α-methylene-δ-lactone neither isomerizes nor couples under similar conditions.
- Raju, Ravinder,Allen, Laura J.,Le, Tri,Taylor, Christopher D.,Howell, Amy R.
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p. 1699 - 1701
(2008/02/02)
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- Cross-metathesis between α-methylene-γ-butyrolactone and olefins: A dramatic additive effect
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Olefin cross-metathesis between α-methylene-γ-butyrolactone and terminal olefins is described. Moderate to excellent yields of α-alkylidene-γ-butyrolactones were obtained with high E-stereoselectivity in the presence of low catalyst loading in refluxing CH 2Cl2. In addition, the use of various additives was found to have a dramatic effect on the efficiency of the cross-metathesis (CM) process by circumventing the formation of the isomerized byproduct.
- Moise, Joelle,Arseniyadis, Stellios,Cossy, Janine
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p. 1695 - 1698
(2008/02/02)
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- Synthesis of substituted 3-furan-2(5H)-ones via an anthracene Diels-Alder sequence
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Deprotonation then electrophilic quench of the lactone derived from the Diels-Alder addition adduct of anthracene and maleic anhydride gave α-substituted lactones in good yield. Of particular note was the reaction with chlorotrimethylsilane which gave only the C-silylated product. Flash vacuum pyrolysis (FVP) of the alkylated products afforded 3-substituted furan-2(5H)-ones in good overall yield.
- Jones, Simon,Wilson, Ian
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p. 4377 - 4380
(2007/10/03)
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- Odorless diphenyl diselenide and disulfide: Syntheses and applications
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Bis[4-(trimethylsilyl)phenyl]diselenide (3) and bis[4-(trimethylsilyl) phenyl]disulfide (31) are found to be odorless equivalents of the commonly used diphenyl diselenide and diphenyl disulfide, respectively. The diselenide 3 is shown to be useful in the preparation of odorless selenium(II) chloride 26 and selenium(IV) trichloride 28 that follow similar reactivity patterns to their phenyl derivatives and can be stored refrigerated under dry conditions. The corresponding selenium(II) bromide had to be prepared fresh from 3 before use. It is also shown that the trimethylsilyl group in the sulfide products can be protodesilylated quantitatively using TFA. Georg Thieme Verlag Stuttgart.
- Patra, Pranab K.,Shanmugasundaram, Kandasamy,Matoba, Manabu,Nishide, Kiyoharu,Kajimoto, Tetsuya,Node, Manabu
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p. 447 - 457
(2007/10/03)
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- A concise synthesis of siphonodictidine
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Siphonodictidine (1) has been synthesized for the first time in a concise and regiocontrolled manner by using 2-(tert-butyldimethylsiloxy)-3-methylfuran (6) as the crucial building block. The silver trifluoro-acetate-induced alkylation of 6 with Ω-bromogeranyl acetate 7 gave the key γ-lactone intermediate 8, which on subsequent reduction, conversion of the hydroxyl into the amino group, and amidination afforded siphonodictidine (1) in an overall yield of 25.7% from 6.
- Jefford, Charles W.,Rossier, Jean-Claude,Boukouvalas, John,Sledeski, Adam W.,Huang, Ping-Zhong
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p. 1383 - 1386
(2007/10/03)
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- Ruthenium-Catalyzed Cyclocarbonylation of Allenyl Alcohols and Amines: Selective Synthesis of Lactones and Lactams
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Allenyl alcohols such as 4-hydroxybuta-1,2-dienes and 5-hydroxypenta-1,2-dienes having a variety of substituents undergo cyclocarbonylation in the presence of a ruthenium catalyst under mild conditions selectively to give five- and six-membered lactones in a high yield with 100% atom economy. 5-Aminopenta-1,2-dines are also cyclocarbonylated to give γ-lactams. A possible carbonylation mechanism involving a ruthenium cluster intermediate is proposed on the basis of experimental results.
- Yoneda, Eiji,Zhang, Shi-Wei,Zhou, Da-Yang,Onitsuka, Kiyotaka,Takahashi, Shigetoshi
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p. 8571 - 8576
(2007/10/03)
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- Stereoselective synthesis of freelingyne and related γ-alkylidenebutenolides via vinylogous Mukaiyama aldol additions
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Following the strategy of Scheme 1, a Mukaiyama aldol addition/anti-elimination route to stereopure γ-alkylidenebutenolides 4 was established. The addition giving 27 was only moderately diastereoselective but the products lk- and ul-27 were chromatographically separable (Scheme 4). They underwent highly selective anti-eliminations in the presence of triflic anhydride-pyridine or Burgess' reagent, furnishing the thiophene-containing butenolides Z- and E-28, respectively (Scheme 5). The Mukaiyama aldol addition leading to compound 29 was 100% lk-selective when mediated by BF3 etherate and 87 : 13 ul-selective in the presence of ZnBr2 (Scheme 6). Stephens-Castro couplings of the resulting butenolides lk- and ul-29 with 3-ethynylfuran proceeded with complete conservation of the stereochemical integrity (Scheme 7). The subsequent anti-eliminations of water were best realized by treatment with DEAD-PPh3. They provided freelingyne (Z-9) with ds = 92 : 8 and its isomer E-9 with ds = 98 : 2 (Scheme 8). Analogously, the differently substituted (trimethylsiloxy)furans 15 or 16 provided the freelingyne analogs Z-10, E-10 and Z-11 (Schemes 6-8).
- Von der Ohe,Bruckner
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p. 659 - 669
(2007/10/03)
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- Use of Winterfeldt's template to control the C-2' configuration in the synthesis of strigol-type compounds
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A route comprising (i) a cycloaddition reaction of citraconic anhydride with the Winterfeldt auxiliary, (ii) hydride reduction of the cycloadduct, (iii) a (formal) ether formation, and (iv) a cycloreversion reaction allows efficient stereocontrol at C-2' in the synthesis of strigol and its structural analogues.
- Roehrig, Susanne,Hennig, Lothar,Findeisen, Matthias,Welzel, Peter,Mueller, Dietrich
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p. 3439 - 3456
(2007/10/03)
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- Influence of 1,4-Bis(diphenylphosphino)butane on the Hydroformylation of α,β-Unsaturated Esters Catalyzed by Zwitterionic, Cationic, and Neutral Rhodium(I) Complexes. The Asymmetric Hydroformylation od α-Methylene-γ-Butyrolactone
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An investigation was made of the effect of 1,4-bis(diphenylphosphino)butane (dppb) on the regioselectivity of the hydroformylation of α,β-unsaturated esters with synthesis gas, catalyzed by rhodium(I) complexes.Excellent regioselectivity was obtained when dppb was added as a ligand for the reaction of methyl acrylate and α-methylene-γ-butyrolactone with synthesis gas.However, it inhibits the reaction when methyl methacrylate is used as the substrate.The asymmetric hydroformylation of α-methylene-γ-butyrolactone using (+)Cl(-) as the catalyst and (R)-BINAP as the chiral ligand (6:1 ratio of (R)-BINAP/Rh) gave an aldehydic lactone, containing a quaternary chiral center, in up to 37percent ee.
- Lee, Chul Woo,Alper, Howard
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p. 499 - 503
(2007/10/02)
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- Preparation of α-Hydroxy-γ-lactones and their Application in the Synthesis of α,β-Butenolides, α-Alkylidene-γ-lactones and Furans
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A straightforward synthesis of α-hydroxy-γ-butyrolactones was carried out by condensation reaction of the lithium anion of ethoxyethyl-protected cyanohydrins with epoxides, followed by acidic treatment.Synthetic applications of these synthons in the preparation of interesting α,β-butenolides, α-alkylidene-γ-lactones and furans are described.
- Munoz, A. Heber,Tamariz, Joaquin,Jimenez, Rogelio,Mora, Gustavo Garcia de la
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p. 501 - 522
(2007/10/02)
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- A useful synthesis of 3-methyl-2(5H)-furanone
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An efficient procedure for the preparation of furanone 3 from commercially available starting material lactone 1, is reported.
- Cruz-Almanza,Padilla Higareda
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p. 1097 - 1104
(2007/10/02)
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- A short route to furanosesquiterpenes using a new siloxyfuran building block. The synthesis of freelingnite and dehydrolasiosperman
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The utility of 2-(tert-butyldimethylsiloxy)-3-methylfuran for the regioselective assembly of furanosesquiterpenes is demonstrated by the syntheses of (±)-freelingnite and dehydrolasiosperman.
- Jefford,Sledeski,Rossier,Boukouvalas
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p. 5741 - 5744
(2007/10/02)
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- Manufacture of gamma-crotonolactone by carbonylation of glycidol
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A process for preparing a substituted or unsubstituted gamma-crotonolactone is provided which comprises reacting a substituted or unsubstituted glycidol of the formula: STR1 wherein R1, R2, R3 and R4 are the same or different and are H, alkyl of from 1 to 40 carbon atoms or aryl of from 6 to 18 carbon atoms, with carbon monoxide in the presence of a carbonylation catalyst to provide a corresponding beta-hydroxy lactone of the formula: STR2 and dehydrating said beta-hydroxy lactone to provide the corresponding gamma-crotonolactone of the formula: STR3
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- Cobalt-mediated Reactions in Synthesis. The Degradation of Carboxylic Acids to Functionalised Noralkanes via Acylcobalt Salophen Intermediates
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Arylmethyl- and allyl-carbonylcobalt salophen complexes, e.g. (7), (8), (9), and (22), readily undergo carbon-to-cobalt-bond homolysis and in situ decarbonylation, producing new alkyl radical centres which can be intercepted with oxygen-, nitrogen-, halogen-, sulphur-, and selenium-containing trapping agents leading to functionalised noralkanes.The sequence constitutes a useful, and in some cases more flexible, variant of the classical Hunsdiecker reaction, and amounts to a cobalt equivalent of the Barton radical decarboxylation reaction of carboxylic acids via their corresponding thiohydroxamic esters.In a similar manner, irradiation of the oxy-substituted acylcobalt salen reagents (25) and (26) in the presence of tetramethylpiperidine oxide produces the products (14) and (27), respectively, resulting from homolysis-decarboxylation and alkyl-radical trapping.In the absence of radical-trapping agents, irradiation of (7c) produces (18), and irradiation of (29) leads to the but-2-enolide (32).
- Patel, Vinod F.,Pattenden, Gerald,Thompson, David M.
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p. 2729 - 2734
(2007/10/02)
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- Regioselectivity control in metal hydride reductions of substituted maleic anhydrides
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A systematic study of reductions of unsymmetrically substituted maleic anhydrides by a variety of metal hydride reagents indicates that the high regioselectivity observed in these reactions is controlled chiefly by electronic factors.
- Kayser, Margaret M.,Breau, Livain,Eliev, Sonia,Morand, Peter,Ip, H. S.
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p. 104 - 109
(2007/10/02)
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- Allylic Rearrangement of Cyanophosphates. III. Reaction of Acyclic Enone Cyanophosphates
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Boron trifluoride-catalyzed allylic rearrangement of α,β-unsaturated ketone cyanophosphates (2, 6 and 12) gave (Z)-4-diethylphosphonooxy-2-butenenitriles (3, 8 and 13), while α,β-unsaturated aldehyde cyanophosphates (17a-c) afforded (E)-4-diethylphosphonooxy-2-butenenitriles (18a-c) stereoselectively.The stereo- and regioselective reaction of 2 with several kinds of aromatics in the presence of boron trifluoride etherate afforded (Z)-4-aryl-2-methyl-2-butenenitriles (20) via the SN2' reaction.On the other hand, treatment of 2 with 1-substituted indoles in the presence of boron trifluoride etherate gave 1-amino-2-methylcarbazole derivatives (23a-c).Keywords-α,β-unsaturated ketone; α,β-unsaturated aldehyde; cyanophosphate; allylic rearrangement; boron trifluoride etherate; 2-butenenitrile derivative; SN2' reaction; 1-aminocarbazole derivative
- Kurihara, Takushi,Miki, Masuo,Santo, Kazunori,Harusawa, Shinya,Yoneda, Ryuji
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p. 4620 - 4628
(2007/10/02)
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- Photochemical Bromination of Methyl (E)-2-Methylbut-2-enoate with N-Bromosuccinimide: Formation of 4-Bromo-2-methylbut-2-en-4-olide
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Bromination of methyl (E)-2-methylbut-2-enoate (4) with N-bromosuccinimide under irradiation with light was described.The formation of 4-bromo-2-methylbut-2-en-4-olide (8) in fairly good yield together with the desired methyl (E)-4-bromo-2-methylbut-2-enoate (5), methyl (E)-2-(bromomethyl)but-2-enoate (6), and methyl 2,3-dibromo-2-methylbutanoate (7) was clarified.Methyl (E)-4-(p-formylphenoxy)-2-methylbut-2-enoate (16) was smoothly subject to catalytic hydrogenation using Wilkinson complex, while the rate of the hydrogenation of its geometrical isomer (17) was extremely retarded.
- Ishii, Hisashi,Ishige, Marie,Matsushima, Yoko,Tohojoh, Toshiaki,Ishikawa, Tsutomu,Kawanabe, Eri
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p. 2353 - 2360
(2007/10/02)
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- Oxidation of Alkyl Trimethylsilyl Ketene Acetals with Lead(IV)
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Alkyl trimethylsilyl ketene acetals generated from either esters or lactones react with lead(IV) acetate (LTA) or lead(IV) benzoate (LTB) to afford useful yields of the corresponding α-carboyloxy esters and α-carboyloxy lactones.Yields of the reaction products are optimized by use of the appropriate solvent (methylene chloride or benzene) during oxidation.Alkyl groups such as methyl, ethyl, and tert-butyl are all compatible with the procedure, and lactones containing five-, six-, and seven-membered rings give good yields of oxidation products.
- Rubottom, George M.,Gruber, John M.,Marrero, Roberto,Juve, Henrik D.,Kim, Wan Chong
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p. 4940 - 4944
(2007/10/02)
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- SYNTHESIS OF UNSATURATED BUTYROLACTONES BY PALLADIUM CATALYZED INTRAMOLECULAR CARBOALKOXYLATION OF HOMOALLYLIC CHLOROFORMATES
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We propose a new method for the preparation of α-methylene lactones involving the palladium (0) catalyzed cyclisation of homoallylic chloroformates 1.
- Henin, Francoise,Pete, Jean-Pierre
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p. 4687 - 4690
(2007/10/02)
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- O-SILYLATED ENOLATE PHENYLTHIOALKYLATION: a SYNTHESIS OF α,β-UNSATURATED 5- AND 6-MEMBERED LACTONES.
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ZnBr2-catalysed phenylthioalkylation of keten bis(trimethylsilyl)acetals, obtained from carboxylic acids, with appropriate α-chlorosulphides can be used to prepare γ- and δ-lactones.
- Khan, Hassan A.,Paterson, Ian
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p. 5083 - 5084
(2007/10/02)
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- Reversal of Regioselectivity in the Reduction of gem-Disubstituted Cyclic Carboxylic Acid Anhydrides
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The regioselective partial reduction of gem-disubstituted cyclic carboxylic acid anhydrides to the corresponding γ-lactones with LiAlH4 or NaBH4 is almost completely reversed when potassium tri-s-butylborohydride is used as the reducing agent.
- Morand, Peter,Salvator, Judith,Kayser, Margaret M.
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p. 458 - 459
(2007/10/02)
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- The Preparation of Synthetic Analogues of Strigol
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A range of analogues of the natural germination stimulant, strigol, for parasitic weeds of the genera Striga and Orobanche, has been prepared.Most of the products contain an α-formyl-γ-lactone (or α-formyl-γ-lactam) grouping attached through an enol-ether linkage to the 5-position of a but-2-enolide.Some have shown sufficiently high activities as to warrant large-scale field trials.
- Johnson, Alan W.,Gowda, Gopala,Hassanali, Ahmed,Knox, John,Monaco, Sam,et al.
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p. 1734 - 1743
(2007/10/02)
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- New Synthetic Route for the Preparation of 4-Phenylthio-4-butanolide Derivatives by the Use of the Pummerer Rearrangement
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The Pummerer rearrangement reaction of 2- or 3-substituted 4-(phenylsulfinyl)butyric acids in the presence of an excess amount of acetic anhydride and a catalytic amount of p-toluenesulfonic acid in refluxing toluene for 1 h afforded 2- or 3-substituted 4-phenylthio-4-butanolide (17a-f).Thermolysis in pyridine of 4-phenylsulfinyl 4-butanolides, which were prepared by oxidation of 17a-f, afforded 2- or 3-substituted 2- or 3-buten-4-olides.
- Watanabe, Mikio,Nakamori, Seijin,Hasegawa, Hatsue,Shirai, Kozo,Kumamoto, Takanobu
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p. 817 - 821
(2007/10/02)
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- Regioselectivity of metal hydride reductions of unsymmetrically substituted cyclic anhydrides. Systems where "steric hindrance along the preferred reaction path" rationalization is not applicable
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Metal hydride reductions of planar cyclic anhydrides such as methylmaleic or 3-substituted phthalic anhydrides occur preferentially at the sterically more hindered carbonyl function.This regioselectivity cannot be rationalized in terms of "the most favourable pathway for non-perpendicular attack by a nucleophile" since both carbonyl groups present are equally accessible to non-perpendicular approach.A study which takes into account the alkaline cation and inductive, mesomeric, and steric effects has been conducted for the reduction of several conjugated and aromatic anhydrides.A qualitative interpretation for the regioselectivities observed in these reductions (as well as in reductions already reported in the literature) is suggested.An early transition state for the catalyzed versus late transition state for the non-catalyzed process is proposed.
- Kayser, Margaret M.,Morand, Peter
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p. 2484 - 2490
(2007/10/02)
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