- Catalyst-controlled site-selective asymmetric epoxidation of nerylamine and geranylamine derivatives
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Novel catalysts for site- and enantioselective epoxidation of nerylamine and geranylamine derivatives have been developed. Although mCPBA oxidation took place selectively at the more electron-rich double bond to give the 6,7-epoxides, these catalysts provide the 2,3-epoxides in moderate to high enantioselectivity via the oxidation of the relatively electron-deficient double bond.
- Nobuta, Tomoya,Kawabata, Takeo
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supporting information
p. 9320 - 9323
(2017/08/23)
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- Efficient amide-directed catalytic asymmetric hydroboration
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A series of acyclic β,γ-unsaturated amides are shown to undergo highly regio- (>95%) and enantioselective (93-99% ee) rhodium-catalyzed hydroboration with pinacolborane (PinBH) using simple chiral monophosphite or phosphoramidite ligands in combination wi
- Smith, Sean M.,Thacker, Nathan C.,Takacs, James M.
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p. 3734 - 3735
(2008/09/20)
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- A new efficient route for multigram asymmetric synthesis of alkannin and shikonin
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A short and convergent approach for the synthesis of alkannin, shikonin and shikalkin is presented. A Hauser-type annulation of cyanophthalide 26 with enone 7 affords the complete aromatic system in just one step with concomitant attachment of the entire side chain. Subsequent Corey's oxazaborolidine mediated asymmetric reduction of the above advanced intermediate, leads to the required isomer in high enantiomeric excess. Finally, a selective and high yielding deprotection protocol furnishes the title compounds as pure crystalline precipitates. Thus, a multigram synthesis of shikonin, alkannin and shikalkin is achieved in high yield and enantioselectivity.
- Couladouros, Elias A.,Strongilos, Alexandros T.,Papageorgiou, Vassilios P.,Plyta, Zoi F.
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p. 1795 - 1803
(2007/10/03)
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- Trichodiene Synthase. Synergistic Inhibition by Inorganic Pyrophosphate and Aza Analogs of the Bisabolyl Cation
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A series of aza analogs of the bisabolyl and α-terpinyl cations were tested as inhibitors of the sesquiterpene cyclase, trichodiene synthase.Both (R)- and (S)-16 and (R)- and (S)-13 as well as trimethylamine were only weak inhibitors when incubated alone.In the presence of inorganic pyrophosphate, itself a known competitive inhibitor of trichodiene synthase, all five amines showed strong cooperative competitive inhibition with an enhancement factor estimated to be 10-40.The apparent induced inhibition constant αKJ decreased in going from trimethylamine to the monoterpene analogs 13 and was strongest for the sesquiterpene analogs 16, indicating that both electrostatic and hydrophobic interactions are important in the binding of each intermediate analog.The cyclase showed little discrimination, however, between the individual enantiomers of each inhibitor.
- Cane, David E.,Yang, Guohan,Coates, Robert M.,Pyun, Hyung-Jung,Hohn, Thomas M.
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p. 3454 - 3462
(2007/10/02)
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- 5-Alkylidene-4,5-dihydro-1H-tetrazoles Substituted by Vinyl or Phenyl Groups
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The nitriles 7e-k and 10 are methylated by methyl triflate to afford the N-methylnitrilium triflates 8e-k and 11 which are allowed to react with methyl azide to produce the tetrazolium triflates 9 * F3CSO3 and 12 * F3CSO3.The crystalline hexafluorophospha
- Quast, Helmut,Hergenroether, Thomas
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p. 581 - 590
(2007/10/02)
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- Hydrogen Iodide Strategy for One-Pot Preparation of Allylic Azides, Nitriles, and Phenyl Sulfones from Allylic Alcohols
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Hydrogen iodide, HI, cleanly generated in situ from Me3SiCl/NaI and water in acetonitrile under mild conditions, was found to be an attractive reagent for the conversion of allylic alcohols into allylic iodides which serve as good allylic cation equivalent.Thus, treatment of allylic alcohols with Me3SiCl/NaI/H2O, followed by the substitution with N3-, CN-, and PhSO2- ions in the same flask produced the corresponding allylic compounds bearing azide, cyano, and phenyl sulfonyl functionalities in fair yields.This method provides a useful procedure for the preparation of allylic compounds from easily available allylic alcohols.
- Kanai, Takaya,Kanagawa, Yoshinori,Ishii, Yasutaka
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p. 3274 - 3277
(2007/10/02)
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- Equilibration of 5-Methyl-3-hexen-2-one and 5-Methyl-3-hexen-2-one and of XCH2CH=CYZ/XCH=CHCHYZ Pairs in General
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The equilibrium constant for isomerization of 5-methyl-4-hexen-2-one to trans-5-methyl-3-hexen-2-one in tert-butyl alcohol at 25 deg C has been found to be 0.40, which is smaller by 250-fold than a literature value.This and other equilibrium constants for reactions of the type XCH2CH=CMe2 XCH=CHCHME2 are shown to be consistent with the double bond stabilizing abilities of various groups as measured by equilibrium constants for reactions of the type XCH2CH=CHY XCH=CHCH2Y.The general case of isomerizations of the type XCH2CH=CYZ XCH=CHCHYZ is also discussed.
- Hine, Jack,Linden, Shwn-Meei
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p. 584 - 587
(2007/10/02)
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- Novel process for the synthesis of tricyclo[6.2.2.03,8 ]dodecane derivatives
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A novel process for the preparation of tricyclo[6.2.2.03,8 ]dodecane derivatives is presented. This novel process is applied to the synthesis of the odorant 4-acetyl-1,7,7-trimethyltricyclo[6.2.2.03,8 ]-3-dodecene, also known as 4-ac
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- Manufacture of organic nitriles
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Olefins are converted to nitriles by reacting with hydrogen cyanide in the presence of an organic thiol or sulphide and a catalytic amount of a cuprous salt which is soluble therein; especially for making 3-pentene nitrile from butadiene.
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