- Regioselective and Stereospecific Copper-Catalyzed Deoxygenation of Epoxides to Alkenes
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Two copper salts (Cu(CF3CO2)2 and IMesCuCl) were identified as earth-abundant, inexpensive, but effective metal catalysts together with diazo malonate for chemo-/regioselective and stereospecific deoxygenation of various epoxides with tolerance of common functional groups (alkene, ketone, ester, p-methoxybenzyl, benzyl, tert-butyldimethylsilyl, and triisopropylsilyl). In particular, the unprecedented regioselectivity allowed for the first time monodeoxygenation of diepoxides to alkenyl epoxides. Density functional theory mechanistic studies showed that the deoxygenation occurred by collapsing the free ylide, unfavoring the possible intuitive pathway via cycloreversion of possible oxetane.
- Yu, Jingxun,Zhou, Yu,Lin, Zhenyang,Tong, Rongbiao
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supporting information
p. 4734 - 4737
(2016/09/28)
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- Unusual reactions of (+)-Car-2-ene and (+)-Car-3-ene with aldehydes on K10 clay
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The reactions of (+)-car-2-ene (1) and (+)-car-3-ene (2) with aldehydes in the presence of montmorillonite clay were studied for the first time (Schemes 3 and 5). The major products of these reactions are optically active, substituted hexahydroisobenzofurans, probably formed as a result of an attack of the protonated aldehyde at the cyclopropane ring. Quite unexpectedly, the products are cis-configured at the ring-fusion site; the fact was established by means of quantum-chemical calculations and NMR data. It appeared that the behavior of the 2 : 3 mixture 1/2 in reactions with aldehydes in the presence of K10 clay differed substantially from the reactivities of the corresponding individual monoterpenes. Copyright 2010 Verlag Helvetica Chimica Acta AG, Zuerich, Switzerland.
- Il'Ina, Irina V.,Volcho, Konstantin P.,Korchagina, Dina V.,Salnikov, Georgi E.,Genaev, Alexander M.,Karpova, Elena V.,Salakhutdinov, Nariman F.
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experimental part
p. 2135 - 2150
(2011/02/16)
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- Syntheses with organoboranes - VIII. Transformation of (1S,6R)-(+)-2- carene into (1S,6R)-(+)-3(10)-carene and (1R,5R)-(-)-α-thujene into (1R,5R)- (+)-sabinene
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The transformation of (1S,6R)-(+)-2-carene and (1R,5R)-(-)-α-thujene into (1S,6R)-(+)-3(10)-carene and (1R,5R)-(+)-sabinene, respectively, by metallation-transmetallation-hydrolysis via the corresponding allylic organoborane intermediates is described.
- Zaidlewicz, Marek,Giminska, Malgorzata
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p. 3847 - 3850
(2007/10/03)
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- Chiral Synthesis via Organoboranes. 35. Simple Procedures for the Efficient Recycling of the Terpenyl Chiral Auxiliaries and Convenient Isolation of the Homoallylic Alcohols in Asymmetric Allyl- and Crotylboration of Aldehydes
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Asymmetric allyl- and crotylboration of aldehydes, RCHO, with terpenyl-based allyl- and crotylborane reagents Ter2*BAll (1), Ter2*BCrtZ (2), and Ter2*BCrtE (3, Ter* = Ipc, 4-Icr and 2-Icr; All = allyl and Crt = crotyl), afford Ter2*BOCH*(R)C*(1R)(2R)CH=CH2 intermediates 4.In these reactions, the isolation of homoallylic alcohols, HOCH*(R)C*(1R)(2R)CH=CH2 (5), can be accomplished via oxidation of 4 with alkaline hydrogen peroxide.Unfortunately, oxidative workup destroys the chiral auxiliary and produces a large amount of nonrecyclable byproduct, terpenol (Ter*OH).Further, isolation of the pure homoallylic alcohol by distillation can be difficult if it boils in the range of the abundant byproduct.Therefore, in order to recycle the chiral auxiliaries and isolate the product homoallylic alcohols in an efficient manner, we have developed the following procedures: (1) elimination workup, in which enantiomerically pure α-pinene and Δ2- and Δ3-carenes are liberated from terpenylborinates 4 by treatment with isobutyraldehyde and 1 mol percent BF3*OEt2; (2) ethanolamine workup involving treatment of 4 with ethanolamine (EA) to achieve the precipitation of the ethanolamine adducts (EA-BTer2*, Ter* = Ipc and 2-Icr, 11 and 12) from which the Ter2*BOMe can be easily regenerated; and (3) 8-hydroxyquinoline workup, involving treatment of 4 with 8-hydroxyquinoline (8-HQ) to precipitate the 8-HQ adducts (8-HQ-BTer2*, Ter* = Ipc, 4-Icr and 2-Icr, 13-15), from which the various Ter2*BOMe intermediates can be conveniently liberated.It is hoped that these procedures will significantly enhance the scope of asymmetric allyl-/crotylboration of aldehydes with Ter2*BAll (1), Ter2*BCrtZ (2), and Ter2*BCrtE (3) and serve as excellent alternatives for any catalytic versions yet to be discovered.
- Brown, Herbert C.,Racherla, Uday S.,Liao, Y.,Khanna, Vijay V.
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p. 6608 - 6614
(2007/10/02)
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- Stereospecific Conversions of (+)-2- and (+)-3-Carenes into Optically active Seven-Membered Ring Systems
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The reactions of (+)-2-carene (6b) and (+)-3-carene (15) with iron carbonyls are studied under various conditions.Besides double bond isomerization and interconversion of the two isomeric hydrocarbons, at least two different modes of ring opening leading to six- and seven-membered ring products are observed.Under mild conditions the primary ring opening complex 7b is isolated without loss of sterical information.Carbonylation of 7b under various conditions yields optically active cycloheptene systems 18, 19, and 20 or the bicyclic systems 9b and 10b.
- Eilbracht, Peter,Winkels, Irmgard
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p. 191 - 198
(2007/10/02)
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- SYNTHESIS OF FUSED CYCLOPROPANES FROM γ-STANNYL ALCOHOLS
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Fused cyclopropanes including 3-carene and isosequicarene have been prepared by treatment of γ-stannyl alcohols with thionyl chloride.
- Kadow, John F.,Johnson, Carl R.
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p. 5255 - 5258
(2007/10/02)
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- CYCLOPROPANE FORMATION FROM 4,5-UNSATURATED THIOPHENYLETHERS. CONVERSION OF LIMONENE INTO CAR-2-ENE
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Strong bases can abstract a proton α to a double bond.A phenylthio group γ to that double bond can be eliminated at the same time leading to a cyclopropane ring.The procedure is illustrated by a conversion of limonene into car-2-ene.
- Fourneron, J. D.,Harwood, L. M.,Julia, M.
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p. 693 - 696
(2007/10/02)
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