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| 2. |
- Blid, Jan, et al.
(författare)
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Lewis Acid Mediated [2,3]-Sigmatropic Rearrangement of Allylic Ammonium Ylides
- 2003
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Ingår i: Tetrahedron Letters. - 0040-4039 .- 1359-8562. ; 44:15, s. 3159-3162
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of the Lewis acid mediated [2,3]-sigmatropic rearrangement of allylic ammonium ylides has been conducted by employing various bases and boron Lewis acids. Using BBr3 together with the phosphazene base 6, various allylic amines could be rearranged in good yields with low to excellent diastereoselectivity.
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| 3. |
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| 4. |
- Bäckvall, Jan-Erling, et al.
(författare)
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Evidence for (π-allyl)palladium(II)(quinone) complexes in the palladium-catalyzed 1,4-diacetoxylation of conjugated dienes
- 1988
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Ingår i: Tetrahedron Letters. - 0040-4039 .- 1359-8562. ; 29:18, s. 2243-2246
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Tidskriftsartikel (refereegranskat)abstract
- Evidence for a coordination of p-benzoquinone to palladium in [4-acetoxy-η3-(1,2,3)-cyclohexenyl]-palladium(II) complexes was provided by changes of the 1H NMR chemical shift values of the π-allyl protons and a decrease of the spin-lattice relaxation time constant for the p-benzoquinone protons. The intermediate (π-allyl)palladium(benzoquinone) complexes previously postulated in palladium-catalyzed 1,4-oxidations of 1,3-dienes were detected by NMR spectroscopy.
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| 5. |
- Hortala, L., et al.
(författare)
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Acyl transfer of 8-acetoxy-2-oxazolinylquinoline assisted by hydrogen bonding formation
- 2002
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Ingår i: Tetrahedron Letters. - 0040-4039 .- 1359-8562. ; 43:6, s. 1027-1029
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Tidskriftsartikel (refereegranskat)abstract
- A significant acceleration of acyl transfer has been achieved on 8-acetoxy-2-oxazolinylquinoline in the presence of benzylamine. Comparison of the aminolysis by the new acylating reagent with that of 8-acetoxyquinoline and 8-acetoxyquinoline-2-carbonitrile has been carried out. The results of these experiments suggest that the proximity of a supplementary basic atom to the ester group increases the participation effect of the basic site mainly by formation of a possible second hydrogen bond. The association constant of benzylamine into the basic cavity of 8-methoxy-2-oxazolinylquinoline (K-d = 80 M-1) has been measured by H-1 NMR titration experiments.
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| 6. |
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| 7. |
- Langlet, Abraham, et al.
(författare)
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Synthesis and reaction of 5,5-dinitrobarbituric acid
- 2000
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Ingår i: Tetrahedron Letters. - 0040-4039 .- 1359-8562. ; 41:12, s. 2011-2013
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Tidskriftsartikel (refereegranskat)abstract
- Nitration of barbituric acid at 40°C gave the previously unknown 5,5- dinitrobarbituric acid (3), which readily underwent hydrolysis to dinitroacetylurea (5), which in turn could be hydrolysed in basic media to the potassium salt of dinitromethane. Alloxane was prepared in a one step procedure by thermal decomposition of 5,5-dinitrobarbituric acid in hot acetic acid.
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| 8. |
- Larhed, M, et al.
(författare)
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Rapid microwave-assisted Suzuki coupling on solid-phase
- 1996
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Ingår i: Tetrahedron Letters. - UNIV UPPSALA,CTR BIOMED,DEPT ORGAN PHARMACEUT CHEM,S-75123 UPPSALA,SWEDEN. UNIV UPPSALA,CTR BIOMED,DEPT MED & PHYSIOL CHEM,S-75123 UPPSALA,SWEDEN. : Elsevier BV. - 0040-4039 .- 1359-8562. ; 37:45, s. 8219-8222
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Tidskriftsartikel (refereegranskat)abstract
- Microwave-assisted palladium-catalysed coupling of aryl and heteroaryl boronic acids with iodo- and bromo-substituted benzoic acids, anchored to TentaGel S RAM, provided high isolated yields of coupled products after a reaction time of 3.8 minutes (45 W). Copyright (C) 1996 Elsevier Science Ltd.
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| 9. |
- Lindström, Ulf M., et al.
(författare)
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Microwave-assisted aminolysis of vinylepoxides
- 1999
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Ingår i: Tetrahedron Letters. - 0040-4039 .- 1359-8562. ; 40:52, s. 9273-9276
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Tidskriftsartikel (refereegranskat)abstract
- Di- and trisubstituted vinyl epoxides in NH4OH were subjected to microwave irradn. affording the corresponding vicinal amino alcs. in high yields. The reaction is stereospecific and highly regioselective for addn. at the allylic carbon. [on SciFinder(R)]
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| 10. |
- Löfström, Claes M.G., et al.
(författare)
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BF3-induced rearrangement of aziridinocyclopropanes derived from 2-phenylsulfonyl-1,3-dienes : A new approach to the tropane alkaloid skeleton
- 1996
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Ingår i: Tetrahedron Letters. - : Elsevier BV. - 0040-4039 .- 1359-8562. ; 37:19, s. 3371-3374
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Tidskriftsartikel (refereegranskat)abstract
- Five N-substituted derivatives of 1,2-methylene-3,4-aziridino 2-phenylsulfonyl cycloalkanes (3a-e) were prepared from their corresponding epoxy cyclopropanes via ring opening of the epoxide by sodium azide and subsequent triphenylphosphine induced cyclization. BF3-induced reaction of compounds 3a-e resulted in a rearrangement via a cyclopropyl carbinyl cation intermediate. In the case of tosylaziridine 3c bicyclic product 5, (tropane skeleton), was formed as the major product. With carbamate derivative 3a exclusive rearrangement to fluorocyloheptene 7 took place.
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