- A novel method for the stereoselective formation of trans bicyclic ketones by way of oxidative radical cyclization
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The stereoselective formation of cyanohydrin 4 was achieved by radical cyclization-oxygen trapping reaction of 5 into an intramolecular acrylic nitrile moiety. The cyanohydrin was used for ring closure reaction with a tosylate, providing the bicyclic systems 1 and 2 with a trans ring fusion.
- Takahashi, Takashi,Tomida, Satoshi,Doi, Takayuki
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Read Online
- Copper-catalyzed vinylogous aerobic oxidation of unsaturated compounds with air
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A mild and operationally simple copper-catalyzed vinylogous aerobic oxidation of β,γ- and α,β-unsaturated esters is described. This method features good yields, broad substrate scope, excellent chemo- and regioselectivity, and good functional group tolerance. This method is additionally capable of oxidizing β,γ- and α,β-unsaturated aldehydes, ketones, amides, nitriles, and sulfones. Furthermore, the present catalytic system is suitable for bisvinylogous and trisvinylogous oxidation. Tetramethylguanidine (TMG) was found to be crucial in its role as a base, but we also speculate that it serves as a ligand to copper(II) triflate to produce the active copper(II) catalyst. Mechanistic experiments conducted suggest a plausible reaction pathway via an allylcopper(II) species. Finally, the breadth of scope and power of this methodology are demonstrated through its application to complex natural product substrates.
- Zhang, Hai-Jun,Schuppe, Alexander W.,Pan, Shi-Tao,Chen, Jin-Xiang,Wang, Bo-Ran,Newhouse, Timothy R.,Yin, Liang
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supporting information
p. 5300 - 5310
(2018/04/24)
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- Et2SBr.SbCl5Br: An effective reagent for direct bromonium-induced polyene cyclizations
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It's all about reactivity: Although bromonium-induced cation-π cyclizations are commonly utilized by nature to fashion six-membered rings from a diverse set of polyene precursors, no general laboratory method exists that can achieve the same breadth of substrate scope. An easily synthesized and handled reagent is described (see scheme) that is capable of directly, broadly, and rapidly effecting such reactions in good yield with a variety of geraniol, farnesol, and nerol derivatives.
- Snyder, Scott A.,Treitler, Daniel S.
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supporting information; experimental part
p. 7899 - 7903
(2010/04/02)
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- Influence of heterocyclic and oxime-containing farnesol analogs on quorum sensing and pathogenicity in Candida albicans
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A series of synthetic molecules combining a geranyl backbone with a heterocyclic or oxime head group are quorum-sensing molecules that block the yeast to mycelium transition in the dimorphic fungus Candida albicans. A number of the analogs have an IC50 ≤ 10 μM, a level of potency essentially identical to the natural quorum sensing signal, the sesquiterpene farnesol. Two of the most potent analogs, neither toxic toward healthy mice, display remarkably different effects when co-administered with C. albicans. While neither offers protection from candidiasis, one analog mimics farnesol in acting as a virulence factor, whereas the other has no effect. The results offer the first example of highly potent synthetic fungal quorum-sensing molecules, and provide the first evidence for the ability to decouple quorum sensing and virulence.
- Shchepin, Roman,Navarathna, Dhammika H.M.L.P.,Dumitru, Raluca,Lippold, Shane,Nickerson, Kenneth W.,Dussault, Patrick H.
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p. 1842 - 1848
(2008/09/20)
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- A Convenient Synthesis of A-Ring-Functionalized Podolactones. Revision of the Structure of Wentilactone B
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(Matrix Presented) A new route to podolactones functionalized in the A ring has been achieved. Two key steps were employed in this synthesis, the construction of the bicyclic skeleton via a Mn(III)-mediated radical cyclization and the transformation of this bicyclic intermediate into the tetracyclic podolactone skeleton through a Pd (II)-mediated bislactonization of the corresponding conjugate diene. The reported synthesis of 3β-hydroxy-13,14,15,-16-tetranorlabda-7,9(11)-dien-(19,6β),(12,17)- diolide (1) let us reassign the structure of wentilactone B, for which structure 1 was wrongly reported.
- Barrero, Alejandro F.,Herrador, Maria M.,Quilez Del Moral, Jose F.,Valdivia, Monica V.
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p. 1379 - 1382
(2007/10/03)
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- A facile one-pot cyanation of primary and secondary alcohols. Application of some new Mitsunobu reagents
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Some new Mitsunobu reagents, especially N,N,N',N'-tetramethylazodicarboxamide(TMAD)-tributylphosphine (TBP) and cyanomethylenetrimethylphosphorane (CMMP), mediated the direct transformation of primary and secondary alcohols into the corresponding nitriles in the presence of acetone cyanohydrin. This type of cyanation process can convert 3β-cholestanol to 3α-cyanocholestane in high yield with complete Walden inversion.
- Tsunoda, Tetsuto,Uemoto, Kaori,Nagino, Chisato,Kawamura, Megumi,Kaku, Hiroto,Ito, Sho
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p. 7355 - 7358
(2007/10/03)
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- Polyene cascade cyclizations mediated by BF3·CH3NO2· an unusually efficient method for the direct, stereospecific synthesis of polycyclic intermediates via cationic initiation at non-functionalized 3° alkenes. An application to the total synthesis of (±)-taxodione
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Convenient stock solutions of BF3 gas in nitromethane have been shown to promote "H+ catalyzed" polyene cyclizations that proceed with excellent levels of regio- and stereocontrol. A direct comparison of this new method for effecting cationic polyannulations to several modern as well as classical procedures has conclusively defined the preparative advantages of the BF3·CH3NO2 medium. The utilization of these new conditions for cationic polycyclization in a concise total synthesis of the antineoplastic agent (±)-taxodione is described.
- Harring, Scott R.,Livinghouse, Tom
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p. 9229 - 9254
(2007/10/02)
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- Cyanation of Allylic Carbonates and Acetates Using Trimethylsilyl Cyanide Catalyzed by Palladium Complex
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Allylic carbonates and acetates are cyanated with trimethylsilyl cyanide in the presence of a catalytic amount (5 mol percent based on the allylic substrates) od Pd(PPh3)4 or Pd(CO)(PPh3)3 in THF under reflux to afford β,γ-unsaturated nitriles in high yields.
- Tsuji, Yasushi,Yamada, Naoaki,Tanaka, Shinsuke
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- Cyano Phosphate: An Efficient Intermediate for the Chemoselective Conversion of Carbonyl Compounds to Nitriles
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Cyanohydrin diethyl phosphates, readily obtained from various ketones and aldehydes by reaction with diethyl phosphorocyanidate and lithium cyanide, reacted chemoselectively with samarium(II) iodide in THF to give the corresponding nitriles in excellent yields.This method was also found applicable to α,β-unsaturated carbonyl compounds via cyano phosphates to give β,γ-unsaturated nitriles, not obtainable by standard methods, without isomerization of the double bonds.
- Yoneda, Ryuji,Harusawa, Shinya,Kurihara, Takushi
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p. 1827 - 1832
(2007/10/02)
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- Dephosphorylation of Cyano Diethyl Phosphates by Reduction with Lithium-Liquid Ammonia: An Efficient Method for Conversion of Carbonyl Compounds into Nitriles
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Cyano diethyl phosphate derivatives of aromatic carbonyl compounds and α,β-unsaturated ketones were successively dephosphorylated by reduction with lithium in liquid ammonia followed by treatment with isoprene or alkyl halides to give β,γ-unsaturated nitriles or α-alkyl-β,γ-unsaturated nitriles in moderate to good yields.
- Yoneda, Ryuji,Osaki, Takahiro,Harusawa, Shinya,Kurihara, Takushi
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p. 607 - 610
(2007/10/02)
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- CYANOPHOSPHATE: AN EFFICIENT INTERMEDIATE FOR CONVERSION OF CARBONYL COMPOUNDS TO NITRILES
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A novel and high yield conversion of saturated or unsaturated carbonyl compounds to nitriles via cyanophosphates by samarium diiodide in the presence of tert-butanol is described.
- Yoneda, Ryuji,Harusawa, Shinya,Kurihara, Takushi
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p. 3681 - 3684
(2007/10/02)
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- SYNTHESIS OF (4E,8E,2S,3R,2'R)-N-2'-HYDROXYHEXADECANOYL-9-METHYL-4,8-SPHINGADIENINE, THE CERAMIDE PORTION OF THE FRUITING-INDUCING CEREBROSIDE IN A BASIDIOMYCETE SCHIZOPHYLLUM COMMUNE, AND ITS (2R,3S)-ISOMER
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A synthesis of the natural enantiomer as well as its diastereomer of the title compound was accomplished, confirming the structure proposed for the fruiting-inducing cerebroside of Schizophyllum commune.
- Mori, Kenji,Funaki, Yuji
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p. 2369 - 2378
(2007/10/02)
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- Insect Juvenile Hormone Analogues: Part XI - Synthesis of Some Heteroaromatic Undecenyl and Geranyl Amides and Their Homologues
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Synthesis of some heteroaromatic long chain amides and the corresponding amines starting from undecenoic acid, 4,8-dimethyl-3(E),7-nonadienoic acid (III) and 5,9-dimethyl-4(E),8-decadienoic acid (V) and a few heteroaromatic amines are described.The compounds have been tested on common Indian red cotton bug for their JH activity.
- Vig, O. P.,Trehan, I. R.,Kad, G. L.,Bedi, Asha Lata,Ghose, J.
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p. 1052 - 1055
(2007/10/02)
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- Reaction of Allyl Diphenyl Phosphates with Soft Bases
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The title phosphates were found to react with a variety of soft bases to give nucleophilic substitution products in high yields.The reaction proceeded regiospecifically under mild reaction conditions with preservation of the double bond geometry.
- Araki, Shuki,Minami, Kazuhiro,Butsugan, Yasuo
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p. 629 - 630
(2007/10/02)
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- Selective Bromination of Polyenes by 2,4,4,6-tetrabromocyclohexa-2,5-dienone
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2,4,4,6-Tetrabromocyclohexa-2,5-dienone (TBCO) liberates bromonium ion when treated with polyenes to form brominated products.The results of the reaction of TBCO with simple olefins are presented.The analogous bromo-ketones, 4-bromo-2,4,6-trichloro- and 2,4,6-tribromo-4-methyl-cyclohexa-2,5-dienone, (4) and (5) respectively, afford the same products (3a), (6), and (7) when treated with geranyl cyanide (1; R = CN).The evidence suggests that formation of the dibromide (3a) may be due to sequential reactions.TBCO in the presence of cetyltrimethylammonium bromide serves as an excellent reagent for selective bromination of polyenes under very mild conditions.
- Kato, Tadahiro,Ichinose, Isao
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p. 1051 - 1056
(2007/10/02)
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