- Synthesis of the Conjugated Tetraene Acid Side Chain of Mycolactone e by Suzuki-Miyaura Cross-Coupling Reaction of Alkenyl Boronates
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The conjugated tetraene acid side chain of mycolactone E has been synthesized by the cross-coupling reaction of a trisubstituted triene bromide with a trisubstituted alkenyl boronate catalyzed by Pd(OAc)2-Aphos-Y under mildly basic conditions [K3PO4·3H2O, H2O, tetrahydrofuran (THF), 35 C, 18 h]. The conjugated tetraene product was obtained in 85 % yield without geometrical isomer(s) under the catalytic conditions. These results demonstrated that the coupling of alkenyl halides with alkenyl boronates catalyzed by Pd(OAc)2-Aphos-Y in combination with CuI-catalyzed regio- and stereoselective alkyne borylation offers an efficient synthetic tool for accessing conjugated polyene molecules.
- Wang, Yuan,Dai, Wei-Min
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supporting information
p. 323 - 330
(2015/10/05)
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- Synthesis of the conjugated tetraene acid side chain of mycolactone e by Suzuki-Miyaura cross-coupling reaction of alkenyl boronates
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The conjugated tetraene acid side chain of mycolactone E has been synthesized by the cross-coupling reaction of a trisubstituted triene bromide with a trisubstituted alkenyl boronate catalyzed by Pd(OAc)2-Aphos-Y under mildly basic conditions [K3PO4·3H 2O, H2O, tetrahydrofuran (THF), 35 °C, 18 h]. The conjugated tetraene product was obtained in 85 % yield without geometrical isomer(s) under the catalytic conditions. These results demonstrated that the coupling of alkenyl halides with alkenyl boronates catalyzed by Pd(OAc) 2-Aphos-Y in combination with CuI-catalyzed regio- and stereoselective alkyne borylation offers an efficient synthetic tool for accessing conjugated polyene molecules. Gently united: Conjugate polyenes possessing trisubstituted double bond(s) are synthesized from trisubstituted alkenyl halides and trisubstituted boronates in high yields under the catalysis of the hemilabile P,O ligand Aphos-Y and Pd(OAc)2 in the presence of K3PO4·3H2O (3 equiv.) and H2O (18 equiv.) in tetrahydrofuran (THF) at 35°C. The product is free of geometric isomers. Copyright
- Wang, Yuan,Dai, Wei-Min
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supporting information
p. 323 - 330
(2014/01/23)
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- Single-electron/pericyclic cascade for the synthesis of dienes
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The highly efficient and diastereoselective synthesis of E dienes has been accomplished through radical cyclization of bromoallyl hydrazones. This methodology has been further extended to generate these products through a one-pot condensation/radical cyclization/cycloreversion cascade from simple aldehyde starting materials in high yields (>75 %) and high diastereoselectivities (>95:5). Mechanistic investigations suggest that the cascade reaction proceeds through a cyclic diazene intermediate prior to the cycloreversion.
- Campbell, Natalie E.,Sammis, Glenn M.
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supporting information
p. 6228 - 6231
(2014/06/23)
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- Total synthesis of naturally configured pyrrhoxanthin, a carotenoid butenolide from plankton
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A carotenoid from the chemical kitchen: Two sequential Stille couplings of an unsymmetric distannane building block with a bromoolefin and a bromoalkyne terminated a highly convergent synthesis of the title compound, pyrrhoxanthin (see scheme).
- Burghart, Johen,Brueckner, Reinhard
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scheme or table
p. 7664 - 7668
(2009/04/11)
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- Enantioselective total syntheses of omuralide, 7-epi-omuralide, and (+)-lactacystin
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(Chemical Equation Presented) An alkylidene carbene 1,5-CH insertion has been used as a key step in an enantioselective total syntheses of omuralide, its C7-epimer, and (+)-lactacystin. An additional noteworthy feature of the synthesis is the use of a nov
- Hayes, Christopher J.,Sherlock, Alexandra E.,Green, Martin P.,Wilson, Claire,Blake, Alexander J.,Selby, Matthew D.,Prodger, Jeremy C.
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p. 2041 - 2051
(2008/09/19)
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- Studies on the synthesis of apoptolidin A. 1. Synthesis of the C(1)-C(11) fragment
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(Chemical Equation Presented) A synthesis of the C(1)-C(11) fragment of apoptolidin A has been accomplished by a convergent route involving the stereoselective glycosidation of 9 and the Suzuki cross-coupling reaction of bromodienoate 7 and the vinylboran
- Handa, Masaki,Scheldt, Karl A.,Bossart, Martin,Zheng, Nan,Roush, William R.
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p. 1031 - 1035
(2008/09/18)
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- Enantioselective synthesis of a trans-7,8-dimethoxycalamenene
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trans-7,8-Dimethoxy-11,12-dehydrocalamenene, a projected intermediate for the total synthesis of marine serrulatane and amphilectane diterpenes, was efficiently synthesized. Starting from a styrene, asymmetric Rh-catalyzed hydroboration using a novel chiral P.P-bidentate ligand afforded an organoboron intermediate (93% ee) which was directly used for C-C bond formation (double homologation, Suzuki coupling). The 1,4-trans-disubstituted tetralin skeleton was selectively formed by a Friedel-Crafts-type catlonic cyclization under strictly aprotic conditions (Me2AlCl) to suppress a remarkable proton-catalyzed disproportionation via diastereoselective hydride transfer.
- Werle, Susen,Fey, Thorsten,Neudoerfl, Joerg M.,Schmalz, Hans-Guenther
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p. 3555 - 3558
(2008/02/12)
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- Total synthesis of paracentrone, C31-allenic opo-carotenoid
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The stereocontrolled total synthesis of a C31-allenic apocarotenoid, paracentrone, was achieved by the convergent C20 + C11 = C31 strategy. The key elements of our synthesis were the Pd-catalyzed cross-coupling to stereoselectively construct the conjugated polyene backbone skeleton and the designed geometrical isomerization at the central double bond of the conjugated polyene chain. In addition, the terminal oxygenated cyclohexane ring having the allenic moiety was prepared by the highly diastereoselective Sharpless epoxidation under our own reaction conditions. The Royal Society of Chemistry 2005.
- Murakami, Yusuke,Nakano, Masayuki,Shimofusa, Takuya,Furuichi, Noriyuki,Katsumura, Shigeo
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p. 1372 - 1374
(2007/10/03)
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- Total Synthesis of the Anthelmintic Macrolide Avermectin B1a
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A highly convergent total synthesis of the anthelmintic macrolide avermectin B1a is described.The key features of this synthesis include the introduction of the C(11)-C(15) portion by selective ring opening of a symmetrical 1,4-bis-epoxide 4 followed by reaction with the anion derived from the 3-methyl-2-(1-methylpropyl)-6-phenylsulphonylpyran 3 to afford the 'northern' C(11)-C(25) fragment 39.Coupling of the derived C(11)-C(25) aldehyde unit 42 with a C(1)-C(10) 'southern' fragment 2 was achieved via a novel deconjugative vinyl sulphone anion sequence.Macrolactonisation and subsequent introduction of the 3,4-double bond gave the aglycone portion 51.The oleandrosyloleandrose disaccharide was introduced by a novel silver-mediated coupling between the 5-acetylated aglycone 70 and the thiocarbonylimidazolide 69.Final deacetylation was accomplished using Super-Hydride to give the natural product 1.
- Ley, Steven V.,Armstrong, Alan,Diez-Martin, David,Ford, Mark J.,Grice, Peter,et al.
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p. 667 - 692
(2007/10/02)
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- Palladium-Catalyzed Syntheses of Conjugated Polyenes
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Conjugated trienes have been prepared by the palladium-catalyzed reaction of vinylic bromides with 2,4-pentadienoic acid and its 3-methyl derivative, in the presence of triethylamine.Methyl (E)-3-bromo-2-methylpropenoate also forms conjugated trienes and in some instances also tetraenes when it is reacted with 1,3-dienes under similar conditions.Some loss of stereochemistry in the starting vinylic bromide or, more often, in the diene may occur in the rections presumably because equilibrating ?-allylic intermediates are involved.1,3,5-Hexatriene and 2 equiv of methyl (E)-3-bromo-3-methylpropenoate form orange-red dimethyl (E,E,E,E,E)-2,11-dimethyl-2,4,6,8,10-dodecapentaenedioate in modest yield.
- Fischetti, William,Mak, K. Tim,Stakem, F. Gregory,Kim, Jin-Il,Rheingold, Arnold L.,Heck, Richard F.
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p. 948 - 955
(2007/10/02)
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