- Total synthesis of 2′-O-methylmyxalamide D and (6E)-2′-O- methylmyxalamide D
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Hetero-bis-metalated 1,3,5-hexatrienes are employed in the linchpin coupling of synthetic fragments for the convergent construction of the central pentaene of the antifungal agent 2′-O-methylmyxalamide D and its (6E) isomer. Sequential Stille and Suzuki-Miyaura couplings interpolate the boron/tin triene into the pentaene chain. The total synthesis of O-methylmyxalamide D and its (6E) isomer was accomplished efficiently. Copyright
- Coleman, Robert S.,Lu, Xiaoling,Modolo, Isabelle
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- Vibrational spectra, conformations, ab initio calculations and vibrational assignments of 3-pentyn-2-ol
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The infrared spectra of 3-pentyn-2-ol, CH3C{triple bond, long}CCH(OH)CH3, have been recorded as a vapour and liquid at ambient temperature, as a solid at 78 K in the 4000-50 cm-1 range and isolated in an argon matrix at ca. 5 K. Infrared spectra of the solid phase at 78 K were obtained before and after annealing to temperatures of 120 and 130 K. The IR spectra of the solid were quite similar to that of the liquid. Raman spectra of the liquid were recorded at room temperature and at various temperatures between 295 and 153 K. Spectra of an amorphous and annealed solid were recorded at 78 K. In the variable temperature Raman spectra, some bands changed in relative intensity and were interpreted in terms of conformational equilibria between the three possible conformers. Complete assignments were made for all the bands of the most stable conformer in which OH is oriented anti to C1(aMe). From various bands assigned to a second conformer in which OH is oriented anti to Hgem(aH), the conformational enthalpy differences was found to be between 0.4 and 0.8 kJ mol-1. The highest energy conformer with OH anti to C3(aC) was not detected. Quantum-chemical calculations have been carried out at the MP2 and B3LYP levels with a variety of basis sets. Except for small basis set calculations for which the aH conformer had slightly lower energy, all the calculations revealed that aMe was the low energy conformer. The B3LYP/cc-pVTZ calculations suggested the aMe conformer as more stable by 0.8 and 8.3 kJ mol-1 relative to aH an aC, respectively. Vibrational wavenumbers and infrared and Raman band intensities for two of the three conformers are reported from B3LYP/cc-pVTZ calculations.
- Horn, Anne,Klaeboe, Peter,Nielsen, Claus J.,Guirgis, Gamil A.
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- Convenient generation of 1-propynyllithium. One-pot synthesis of acetylenic carbinols from 1,2-dibromopropane and aldehydes and ketones
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Treatment of 1,2-dibromopropane (1) with 3 equiv of lithium diisopropylamide (-60° to 0°C, THF) generates 1-propynyllithium (2), which with aldehydes or ketones affords acetylenic carbinols 3 in 82-96% yields.
- Gribble,Joyner,Switzer
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- Spectroscopy and Photochemistry of Triplet 1,3-Dimethylpropynylidene (MeC3Me)
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Photolysis (λ > 472 nm) of 2-diazo-3-pentyne (11) affords triplet 1,3-dimethylpropynylidene (MeC3Me, 33), which was characterized spectroscopically in cryogenic matrices. The infrared, electronic absorption, and electron paramagnetic resonance spectra of MeC3Me (33) are compared with those of the parent system (HC3H) to ascertain the effect of alkyl substituents on delocalized carbon chains of this type. Quantum chemical calculations (CCSD(T)/ANO1) predict an unsymmetrical equilibrium structure for triplet MeC3Me (33), but they also reveal a very shallow potential energy surface. The experimental IR spectrum of triplet MeC3Me (33) is best interpreted in terms of a quasilinear, axially symmetric structure. EPR spectra yield zero-field splitting parameters that are typical for triplet carbenes with axial symmetry (|D/hc| = 0.63 cm-1, |E/hc| = β 0 cm-1), while theoretical analysis suggests that the methyl substituents confer significant spin polarization to the carbon chain. Upon irradiation into the near-UV electronic absorption (λmax 350 nm), MeC3Me (33) undergoes 1,2-hydrogen migration to yield pent-1-en-3-yne (4), a photochemical reaction that is typical of carbenes bearing a methyl substituent. This facile process apparently precludes photoisomerization to other interesting C5H6 isomers, in contrast to the rich photochemistry of the parent C3H2 system.
- Knezz, Stephanie N.,Waltz, Terese A.,Haenni, Benjamin C.,Burrmann, Nicola J.,McMahon, Robert J.
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- Synthesis and characterization of all four diastereomers of 3,4-dichloro-2-pentanol, motifs relevant to the chlorosulfolipids
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All four diastereomers of 3,4-dichloro-2-pentanol were synthesized by anti-dichlorination of the precursor allylic alcohols; their stereochemistry was elucidated by X-ray crystallographic analysis of tosylate derivatives. Complete NMR data is provided in
- Kanady, Jacob S.,Nguyen, John D.,Ziller, Joseph W.,Vanderwal, Christopher D.
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- Unified Approach to Furan Natural Products via Phosphine-Palladium Catalysis
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Polyalkyl furans are widespread in nature, often performing important biological roles. Despite a plethora of methods for the synthesis of tetrasubstituted furans, the construction of tetraalkyl furans remains non-trivial. The prevalence of alkyl groups in bioactive furan natural products, combined with the desirable bioactivities of tetraalkyl furans, calls for a general synthetic protocol for polyalkyl furans. This paper describes a Michael–Heck approach, using sequential phosphine-palladium catalysis, for the preparation of various polyalkyl furans from readily available precursors. The versatility of this method is illustrated by the total syntheses of nine distinct polyalkylated furan natural products belonging to different classes, namely the furanoterpenes rosefuran, sesquirosefuran, and mikanifuran; the marine natural products plakorsins A, B, and D and plakorsin D methyl ester; and the furan fatty acids 3D5 and hydromumiamicin.
- Chen, Violet Yijang,Kwon, Ohyun
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supporting information
p. 8874 - 8881
(2021/03/17)
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- Stereoselective Synthesis of the C1-C22 Carbon Framework of (-)-Amphidinolide K
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Two stereoselective routes to the C7-C22 subunit of amphidinolide K are disclosed. Jacobsen's hydrolytic kinetic resolution and Sharpless' asymmetric dihydroxylation reactions have been employed for the construction of the tetrahydrofuran ring. The C10-C1
- Chandankar, Somnath S.,Raghavan, Sadagopan
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p. 9584 - 9602
(2019/09/06)
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- Propene as an Atom-Economical Linchpin for Concise Total Synthesis of Polyenes: Piericidin A
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A concise and convergent total synthesis of piericidin A is disclosed. The synthesis hinges on the utilization of propene as a synthetic linchpin to merge the properly elaborated alkyne fragments, leading to the 1,3,6-triene motif of piericidin A. Utilization of propene as a unique alkene, capable of sequential coupling with two alkynes, is further illustrated in the context of various 1,3,6-triene products. The latter process proceeds with high atom economy and efficiently gives rise to complex frameworks from readily accessible alkyne substrates. This strategic C-C bond formation offers an orthogonal paradigm in the design of synthetic routes, leading to higher step economy and more efficient syntheses of polyunsaturated natural products.
- Trost, Barry M.,Gholami, Hadi
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supporting information
p. 11623 - 11626
(2018/09/21)
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- MACROCYCLIC PICOLINAMIDES AS FUNGICIDES
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This disclosure relates to macrocyclic picolinamides of Formula (I) described herein, wherein X, Y, R1 and R2 are as defined herein and to their use as fungicides in a formulation comprising a phytologically acceptable carrier. Also provided are methods of using compounds of Formula (I) in combination with other pesticides including fungicides, insecticides, nematocides, miticides, arthropodicides, bactericides, and combinations thereof.
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Paragraph 0098; 0099
(2016/01/25)
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- Torquoselectivity in the nazarov reactions of allenyl vinyl ketones
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Nazarov reactions mediated by BF3-etherate of a series of carbon-substituted allenyl vinyl ketones provided intermediates in which substituents on the termini of the allenes had rotated away from the vinyl moieties, and these intermediates were
- Morgan, Timothy D. R.,Leblanc, Luc M.,Ardagh, Giselle H.,Boyd, Russell J.,Burnell, D. Jean
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p. 1042 - 1051
(2015/01/30)
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- Highly stereoselective C-C bond formation by rhodium-catalyzed tandem ylide formation/[2,3]-sigmatropic rearrangement between donor/acceptor carbenoids and chiral allylic alcohols
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The tandem ylide formation/[2,3]-sigmatropic rearrangement between donor/acceptor rhodium carbenoids and chiral allyl alcohols is a convergent C-C bond forming process, which generates two vicinal stereogenic centers. Any of the four possible stereoisomers can be selectively synthesized by appropriate combination of the chiral catalyst Rh2(DOSP)4 and the chiral alcohol.
- Li, Zhanjie,Parr, Brendan T.,Davies, Huw M. L.
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supporting information; experimental part
p. 10942 - 10946
(2012/08/07)
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- Total synthesis of carolacton, a highly potent biofilm inhibitor
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Metals are the key players in the synthesis of caralacton, a strong inhibitor of bacterial biofilms. The total synthesis is based on several metal-mediated key transformations such as the Ley and the Duthaler-Hafner aldol reactions, the Marshall reaction and Breit's substitution, as well as the Nozaki-Hiyama-Kishi and Negishi-Fu C-C coupling reactions. Copyright
- Schmidt, Thomas,Kirschning, Andreas
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p. 1063 - 1066
(2012/03/11)
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- Palladium(II)-catalyzed dicarboxymethylation of chiral allylic alcohols: Chirality transfer affording optically active diesters containing three contiguous chiral centers
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This manuscript describes the extension of Stille's palladium-catalyzed olefin dicarbonylation reaction to chiral allylic alcohols with chirality transfer to afford the corresponding chiral alcohol functionalized with bis-carbomethoxy esters, containing three contiguous chiral centers, in good to excellent diastereoselectivities (78-98%).
- Hamed, Othman,Henry, Patrick M.,Becker, Daniel P.
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supporting information; experimental part
p. 3514 - 3517
(2010/09/05)
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- Stereoselective synthesis of erythronolide A via nitrile oxide cycloadditions and related studies
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(Chemical Equation Presented) An expeditious synthesis of erythronolide A is documented. Key steps of the approach include two magnesium-mediated nitrile oxide cycloadditions, a chelation-controlled Grignard reaction, and a Sharpless asymmetric dihydroxylation. 2009 American Chemical Society.
- Muri, Dieter,Carreira, Erick M.
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experimental part
p. 8695 - 8712
(2010/01/15)
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- Multiphoton infrared initiated thermal reactions of esters: Pseudopericyclic eight-centered cis-elimination
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Multiphoton infrared absorption from a focused, pulsed CO2 laser was used to initiate gas-phase thermal reactions of cis- and trans-3-penten-2-yl acetate. By varying the helium buffer gas pressure, it was possible to deduce the product distribution from the initial unimolecular reactions, separate from secondary reactions in a thermal cascade. Thus, trans-3-penten-2-yl acetate gives 54 ± 5% of β-elimination to give trans-1,3-pentadiene, 40 ± 3% of [3,3]-sigmatropic rearrangement to give cis-3-penten-2-yl acetate and 6 ± 4% of cis-1,3-pentadiene. Similar irradiation of cis-3-penten-2-yl acetate gives 45 ± 1% of β-elimination to give cis-1,3-pentadiene, 32 ± 2% of [3,3]-sigmatropic rearrangement to give trans-3-penten-2-yl acetate and 23 ± 2% of trans-1,3-pentadiene. The latter process is an eight-centered δ-elimination, which is argued to be a pseudopericyclic reaction. Although β-eliminations have been suggested to be pericyclic, B3LYP/ 6-31G(d,p), MP2 and MP4 calculations suggest that both β- and δ-eliminations, as well as [3,3]-sigmatropic rearrangements of esters are primarily pseudopericyclic in character, as judged by both geometrical, energetic and transition state aromaticity (NICS) criteria. Small distortions from the ideal pseudopericyclic geometries are argued to reflect small pericyclic contributions. It is further argued that when both pericyclic and pseudopericyclic orbital topologies are allowed and geometrically feasible, the calculated transition state may be the result of proportional mixing of the two states; this offers an explanation of the range of pseudopericyclic and pericyclic characters found in related reactions.
- Ji, Hua,Li, Li,Xu, Xiaolian,Ham, Sihyun,Hammad, Loubna A.,Birney, David M.
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supporting information; experimental part
p. 528 - 537
(2009/06/28)
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- Synthesis of novel 2H,5H-dihydrofuran-3-yl ketones via ISNC reactions
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Unique 1-[2H,5H-dihydrofur-3-yl]ketones have been synthesized from propargylic nitroethers via intramolecular cycloadditions involving silyl nitronates. Various substituent groups were placed on the 2 and 5 positions of the dihydrofuran rings. We examined the scope of the long-range coupling in proton NMR of the oxo-dihydrofuran products. The identities of the diastereomers resulting from the Michael addition/cycloaddition reactions were tentatively assigned for the first time. CAChe MNDO PM5 and CONFLEX programs were engaged to assist with the identification of these stereoisomers. The reaction times and conditions for these oxo-dihydrofurans were found to be different than that of the published dihydrofuranals, which led us to propose a different mechanism.
- Grandbois, Matthew L.,Betsch, Kelsie J.,Buchanan, William D.,Duffy-Matzner, Jetty L.
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supporting information; scheme or table
p. 6446 - 6449
(2011/02/23)
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- Intramolecular Diels-Alder reactions of optically active allenic ketones: Chirality transfer in the preparation of substituted oxa-bridged octalones
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The intramolecular Diels-Alder reaction of allenic ketones containing a furyl unit (IMDAF) to generate oxatricyclic systems in good yields is described. The alkene dienophiles 1ab give poor yields of the cycloadducts 2ab, presumably due to the facile retro Diels-Alder reaction. However, the analogous allenic dienophile 7 afforded the desired cycloadduct 8 in 91% yield on treatment with dimethylaluminum chloride. When the allene bears an alkyl substituent on the terminal carbon, complete diastereoselectivity is seen in the IMDAF, e.g. cyclization of 14 gave only the cycloadduct 15 in 80% yield presumably due to greater steric hindrance in the transition state II as compared to that in I. Finally we report complete chirality transfer of the stereochemistry of an allene to the carbon framework of the oxatricyclic system. Thus, the optically active allenic ketone 20 afforded only the desired cycloadduct 21 with the correct absolute stereochemistry needed for the synthesis of the arisugacin class of natural products. Copyright
- Jung, Michael E.,Min, Sun-Joon
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p. 10834 - 10835
(2007/10/03)
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- Stereocontrolled [4+2]-annulation accessing dihydropyrans: Synthesis of the C1a-C10 fragment of kendomycin
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(Chemical Equation Presented) Development of new organosilane reagents bearing C-centered chirality where the stereocenter is fully substituted, and their use in the stereocontrolled synthesis of cis- and trans-dihydropyrans containing a trisubstituted ol
- Lowe, Jason T.,Panek, James S.
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p. 1529 - 1532
(2007/10/03)
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- Biocatalytic oxidative kinetic resolution of sec-alcohols: Stereocontrol through substrate-modification
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Whole lyophilised cells of Rhodococcus ruber DSM 44541 were employed for the oxidative kinetic resolution of sec-alcohols using acetone as hydrogen acceptor. The enantioselectivity of this process could be controlled effectively by introducing C-C multiple bonds into substrates, which were inefficiently recognised, in particular short-chain (ω-1)-alcohols and (ω-2)-analogs. Thus, the enantioselectivities of rac-2-pentanol (E=16.8) and rac-3-octanol (E=13.3) were significantly improved by introducing a C=C bond adjacent to the alcohol moiety to give racemic (E)-pent-3-en-2-ol and 4-(E)-octen-3-ol, which were resolved with excellent selectivities (E >100 and 50, respectively). In addition, it was found that high stereodifferentiation between the E- and Z-configured double bonds occurred, as the corresponding (Z)-isomers were not converted. Similar selectivity-enhancing effects were observed with acetylenic analogs.
- Stampfer, Wolfgang,Kosjek, Birgit,Faber, Kurt,Kroutil, Wolfgang
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p. 275 - 280
(2007/10/03)
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- The effect of catechin derivatives on the enantioselectivity of lipase-catalyzed hydrolyses of alkynol benzoate esters
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Polyphenols, such as (+)-catechin and pyrogallol could be used to enhance stereochemical control in the lipase-catalyzed hydrolysis of alkynol benzoate esters, leading to increased enantioselectivities in the kinetic resolution of alkynols with lipase Amano AH.
- Nakamura, Kaoru,Takenaka, Keishi
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p. 415 - 422
(2007/10/03)
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- Chelated enolates of amino acid esters - New and efficient nucleophiles for isomerization-free, stereoselective palladium-catalyzed allylic substitutions
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Chelated amino acid ester enolates were found to be suitable nucleophiles for palladium-catalyzed allylic alkylations. Unlike stabilized soft nucleophiles, the chelated enolates react under very mild reaction conditions, even at -78 °C. If TFA protected a
- Kazmaier, Uli,Zumpe, Franz L.
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p. 4067 - 4076
(2007/10/03)
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- Synthesis of β-hydroxy ketones and vinylsilanes from homopropargylic alcohols by intramolecular hydrosilation
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matrix presented Catalytic intramolecular hydrosilation of nonracemic homopropargylic alcohols affords the corresponding five-membered cyclic siloxanes regiospecifically. Oxidation or alkylmetal addition converts these intermediates into β-hydroxy ketones
- Marshall, James A.,Yanik, Mathew M.
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p. 2173 - 2175
(2007/10/03)
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- PalladiumdD-catalyzed exchange and isomerization reactions. 17. Exchange of chiral allyl alcohols with hydroxide, methoxide, and phenyl at high [Cl-]. Stereochemistry of the wacker reaction
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At high [Cl ] (> 2.0 M), PdCl42- catalyzes the exchange of chiral allylic alcohols with hydroxy, methoxy, and phenyl to give chiral allyl-substituted olefins. With unsymmetrical olefins, isomerization occurs along with exchange. The hydroxyl exchange occurs in aqueous solution while the other exchanges are carried out in methanol solution. At low [Cl-] (0.1 M) oxidation to the corresponding β-hydroxy-, methoxy-, and phenyl-substituted carbonyl compounds occurred. The absolute configurations of the oxidation and exchange products should be the same if the same mode of addition to the Pd(II)-β-complex is operative. The absolute configurations of the oxidation and exchange products for the phenylation reaction were the same, while for hydroxy and methoxy they were different. This result indicates methanol and water must have different stereochemistries of addition at high and low [Cl-]. Thus, previous studies showing anti hydroxypalladation at high [Cl-] are not valid indicators of the stereochemistry at low [Cl-]. If anti addition occurs at high [Cl-], the addition must be syn at low [Cl-].
- Hamed, Othman,Henry, Patrick M.,Thompson, Charles
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p. 7745 - 7750
(2007/10/03)
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- (Z)-3-alkylidene-4,5-dihydro-4-hydroxy-5-methyl-2-(3H)-furanones by regio- and diastereoselective ene reaction of singlet oxygen (Schenk reaction) with γ-hydroxy vinylstannanes: An enantioselective synthesis of dihydromahubanolide B
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(Z)-3-Alkylidene-4,5-dihydro-4-hydroxy-5-methyl-2-(3H)-furanones 5 were prepared from appropriately substituted propargylic alcohols 1 by a sequence of hydromagnesation to γ-hydroxy vinylstannanes 2, subsequent photooxygenation and reduction to stannyl diols 3, iododestannylation to iodo diols 4, and finally cyclization by palladium-catalyzed carbonylation (for 5a) or Ni(CO)2(PPh3)2 (for 5b,c). The reaction sequence can be performed enantioselectively by starting with chiral propargylic alcohols. The current approach constitutes a convenient four-step synthesis of optically active lactones 5 from readily available starting materials and is applied herein to the preparation of the natural lactone dihydromahubanolide B.
- Adam,Klug
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p. 567 - 572
(2007/10/02)
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- Iron(I) mediated activation of C-C and C-H bonds of cis- and trans-1-acetyl-2-methylcyclopropanes in the gas phase: Competition between ring cleavage and α-CC-bond insertion reactions
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Unimolecular and collision induced fragmentations of cis- and trans-1-acetyl-2-methylcyclopropanes, complexed to bare Fe+ cations, were examined by means of tandem mass spectrometry. Stereoselective isotopic labeling data as well as comparative studies with acylic isomers reveal that two reaction pathways are in competition with each other. On the one hand, dehydrogenation, loss of ethene, and loss of acetaldehyde proceed via a common intermediate which is formed via ring cleavage of 1-acetyl-2-methylcyclopropane/Fe+ to yield the corresponding 3-hexen-2-one/Fe+ complexes; these undergo subsequently CH- and CC-bond activation via the remote functionalization mechanism. These ring cleavages are associated with a complete loss of stereochemical features for the cis and trans isomers. In contrast, unimolecular decarbonylation occurs stereoselectively and is favored for the trans isomers; this is rationalized via a stereoselective formation of cis- and trans-η3-allyl complexes in the course of the electrocyclic ring-opening process. Furthermore, interconversion reactions, thermodynamic and kinetic aspects, and isotope effects of the CH- and CC-bond activation processes are discussed.
- Schalley, Christoph A.,Schr?der, Detlef,Schwarz, Helmut
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p. 11089 - 11097
(2007/10/02)
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- Convenient synthesis of 4-methylene-2-oxazolidinones and 4-methylenetetrahydro-1,3-oxazin-2-ones via transition-metal catalyzed intramolecular addition of nitrogen atom to actylenic triple bond
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2-Propynyl tosylcarbamates 1 undergo cyclization smoothly by the catalysis of CuCl/Et3N or AgNCO/Et3N to furnish 4-methylene-2-oxazolidinones 2 in good yields. The similar cyclization of the N-acyl derivatives of 1 (PhCO, MeCO, EtOCO, etc.) is catalyzed effectively by AgNCO/t-BuOK. These reactions accommodate a variety of substituents at C1 and C3 of 2-propyn-1-ol and provide (Z)-2 as single stereoisomers. The scope of the cyclization of 3-butynyl carbamates is rather limited, and in general only N-tosyl derivatives of terminally unsubstituted 3-butyn-1-ols undergo cyclization to give 4-methylenetetrahydro-1,3-oxazin-2-ones in synthetically useful yields by the catalysis of AgNCO/Et3N or AgNCO/t-BuOK.
- Tamaru,Kimura,Tanaka,Kure,Yoshida
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p. 2838 - 2849
(2007/10/02)
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- SELECTIVITY IN THE AMINATION OF ALLYLIC ALCOHOLS via INTRAMOLECULAR AMIDOMERCURATION
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Intramolecular amidomercuration reactions of acylaminomethyl derivatives of γ-substituted allylic alcohols were examined.The effect of oxygen substitution on the δ carbon and of the geometry of the double bond on the regiochemistry and stereochemistry of
- Harding, Kenn E.,Hollingsworth, Donald R.
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p. 3789 - 3792
(2007/10/02)
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- Synthesis of Allenylsilanes from Propargyl Carbamates
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Pent-3-yn-2-yl acetate (1) reacts with dimethyl(phenyl)silyl cuprate reagent to give a mixture of allenylsilane and propargylsilane.The corresponding N-phenylcarbamate (4) gives only the allenylsilane.Four other examples of this regioselective reaction are reported.The stereochemistry is largely syn.
- Fleming, Ian,Takaki, Ken,Thomas, Andrew P.
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p. 2269 - 2274
(2007/10/02)
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- ACTION D'ALUMINIQUES DERIVANT DE BROMURES RCCCH2Br SUR LES ACETALS; PREPARATION D'ETHERS α-ALLENIQUES
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Organoaluminium compounds prepared in ether from RCCCH2Br react with acetals to give solely α-allenic ethers.
- Barbot, F.,Miginiac, Ph.
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- Convenient deuterium labeling on a gas-liquid chromatography column. Preparative scale formation of α,β-unsaturated Od-alcohols
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Several α,β-unsaturated ethylenic and acetylenic alcohols 1-11 were conveniently deuterated on oxygen, by a GLC technique, with high yields and 80 to 98percent deuterium incorporation.
- Georgoulis, Constantin,Smadja, William,Ville, Guy
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p. 269 - 270
(2007/10/02)
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