- 9-Oxabicyclo[3.3.1]nona-2,6-diene. Short access and allylic bromination
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9-Oxabicyclo[3.3.1]nona-2, 6-diene (3) has been synthesized from cycloocta-1, 5-diene in two steps in an overall yield of 88%. The dihedral-angle dependence of its 1H solution NMR data and the double signal set of its 13C CP MAS NMR spectrum correspond to the results of the single crystal structure analysis. Reaction of 3 with N-bromosuccinimide in the presence of sodium peroxodisulfate or benzoylperoxide has led in good yield to a dibromo derivative 4, and a tribromo derivative 5, respectively. Compounds 4 and 5 feature two allylic bromine suestituents, while an additional vinylic bromine atom is present in 5. According to a single crystal structure study the lattice of 4 consists of pairs of enantiomers similar to those found in the case of 3.
- Bassioni, Ghada,Delgado, Fernando S.,Jaeggy, Matthieu,K?hler, Frank H.,Nogai, Stefan,Ruiz-Pérez, Catalina
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- Synthesis of enantiopure 9-oxabicyclononanediol derivatives by lipase-catalyzed transformations and determination of their absolute configuration
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Mixtures of endo,endo-9-oxabicyclo[4.2.1]nonane-2,5-diol (meso-2) and endo,endo-9-oxabicyclo[3.3.1]nonane-2,6-diol [(±)-3] were prepared from cycloocta-1,5-diene (1) upon 09174874200 treatment with peracids by transannular O-heterocyclization and subsequent saponification of the formed diol monoesters such as (±)-4 and (±)-5. The corresponding diacetates, meso-6 and (±)-7, were formed by acetylation of either meso-2 and (±)-3 or (±)-4 and (±)-5 with acetic anhydride/pyridine. These diacetates were enantioselectively hydrolyzed by microbial enzymes such as the lipases from Candida antarctica (CAL) or Candida rugosa (CRL). The corresponding enantiomers were formed by lipase-catalyzed acetylation of the diols meso-2 and (±)-3 with vinyl acetate. The skeletal isomers can also be separated in this way because the enantiopure monoacetates 4 were formed from the meso-compounds 2 or 6, while one enantiomer of the racemic diacetate (±)-7 [or the diol (±)-3] was transformed into the enantiopure diol 3 (or the enantiopure diacetate 7, respectively) via the corresponding enantiomers of the monoacetate 5. The other enantiomer remained untouched in both cases. The lipases reacted enantioselectively to give the R isomer. Cycloocta-1,5-diene (1) was also used to synthesize 2-oxa-6-thiatricyclo[3.3.1. 13,7]decane-4,8-diol [(±)-11] in a four-step sequence. This racemic diol was also acetylated selectively (R isomer) with vinyl acetate and CRL. Reductive desulfuration of (±)-11 gave exo,exo-9-oxabicyclo[3.3.1]nonane-2,6-diol [(±)-12], which was acetylated selectively (S isomer) with CRL under the same conditions. The similarity in size and particularly in shape is responsible for the observed stereoselectivity of the lipases for the racemic endo,endo compounds (±)-3 and (±)-7 on the one hand and the exo,exo compound (±)-12 on the other hand. The absolute configuration and crystal packing of the products was determined by X-ray structural analysis. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Hegemann, Klaus,Froehlich, Roland,Haufe, Guenter
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p. 2181 - 2192
(2007/10/03)
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- Synthesis of Cyclic Ethers via Bromine Assisted Epoxide Ring Expansion
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Neighbouring group participation by epoxide oxygen in the opening of bromonium ions results in the stereoselective synthesis of cyclic ethers. 9-Oxabicyclonon-4-ene gives trans, trans-2,6-dibromo-9-oxabicyclononane and trans,trans-2,5-dibromo-9-oxabicyclononane.Sequential bromination and Bu3SnH reduction converts 1,2-epoxyhex-5-ene into cis- and trans-2,5-dimethyltetrahydrofuran and 2-methyltetrahydropyran while (+)-cis-limonene oxide is converted into non-chiral cineole.
- Davies, Stephen G.,Polywka, Mario E. C.,Thomas, Susan E.
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p. 1277 - 1282
(2007/10/02)
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- STEREOSELECTIVE SYNTHESIS OF CYCLIC ETHERS VIA BROMINE ASSISTED EPOXIDE RING EXPANSION
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9-Oxabicyclonon-4-ene reacts with bromine to give stereoselectively trans,trans-2,6-dibromo-9-oxabicyclononane and trans,trans-2,5-dibromo-9-oxabicyclononane.
- Davies, Stephen G.,Polywka, Mario E. C.,Thomas, Susan E.
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p. 1461 - 1464
(2007/10/02)
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- Reactions of Iodine(I) Acetate with Alkenes and Vicinal Diols
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The chemoselectivities of the reactions of iodine(I) acetate and iodine(I) acetate-thallium(I) acetate with cis-cyclooct-5-ene-1,2-diol have been investigated.The addition of iodine(I) acetate to cyclo-octa-1,5-diene, for a number of reagent systems, results in products arising from both 1,2-addition and transannular pathways.
- Cambie, Richard C.,Rutledge, Peter S.,Stewart, Georgina M.,Woodgate, Paul D.,Woodgate, Sheila D.
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p. 1689 - 1698
(2007/10/02)
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- ELECTROPHILE AND SOLVENT DEPENDENT SYNTHESES OF CYCLIC ETHERS FROM (Z,Z)-CYCLOOCTA-1,5-DIENE.
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The isomer ratio in the formation of disubstituted 9-oxabicyclo nonane and 9-oxabicyclo nonane derivatives 2 and 3 by an oxyhalogenation procedure depends on the electrophile and on the solvent utilized.
- Haufe, Guenter
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p. 4365 - 4368
(2007/10/02)
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