Synthese der enantiomeren 1,6-Spiro[4.4]nonadiene

Two new syntheses of spiro[4.4]nonane-1, 6-dione (I) are described: one by rearrangement of 1,6-epoxy-bicyclo[4.3.0]-nonane-2-one (IV) with boron trifluoride, the other by an acid catalyzed, intramolecular Claisen condensation of 4-(2-oxocyclopentyl)-butyric acid. Spiro[4.4]-nonane-1,6-dione is converted into trans, trans-spiro[4.4]nonane-1,6-diol which is resolved into enantiomers via the diastereomeric esters with (?)-camphanic acid. (+)-(5S)-Spiro[4.4]nona-1,6-diene (III) is prepared from (1R, 6R)-trans,trans-spiro[4.4]nonane-1,6-diol (II) by pyrolysis of the corresponding bis-4-methylphenyl-thionocarbonate. This modification of the Chugaev reaction is particularly useful with sterically hindered alcohols which cannot be converted into S-me-thylxanthates. The circular dichroism, UV.- and NMR.-spectrum of optically active spiro[4.4]-nonane-1,6-diene are discussed.     

Straightforward synthesis of 1,6-dioxaspiro[4.4]nonanes

Diols 2, easily prepared by a DTBB-catalysed lithiation of the dithioether 1 in the presence of different carbonyl compounds, react with ozone in dichloromethane at −78 °C leading, after treatment with thiourea at 20 °C, to the corresponding substituted 1,6-dioxaspiro[4.4]nonanes 3.     

Synthesis of homochiral spiro[4.4] nonane-1,6-diols

Homochiral cis,cis-; cis,trans- and trans,trans-spiro[4.4]nonane-1,6-diols were prepared via diastereoselective reduction of enantiomerically pure spiro[4.4]nonane-1,6-dione (1) with the corresponding reducing agents: lithium n-butyldiisobutylaluminium hydride for cis,cis-diol (2) with 88% yield; BH3·THF for cis, trans-diol (3) with 91% yield; LiAlH4 for trans,trans-diol (4) with 15% yield.     

Synthesis of spiro[4.4]nonane-1,6-diols via the hydrogenation of spiro[4.4]nonane-1,6-dione: the profound effect of hydrogenating agents

The synthesis of spiro[4.4]nonane-1,6-diols via the catalytic as well as stoichiometric hydrogenation of spiro[4.4]nonane-1,6-dione was studied. Profound effects of the hydrogenation catalysts and reagents on the stereoselectivity of the products were observed. The choice of solvent also was found to have a significant influence on the product selectivity. The opening of a spiro-ring in the starting material was identified as a major side reaction in alcohol solvents. The absolute configuration of the trans, trans-diol was unambiguously determined by X-ray crystallography.     

5-germaspiro[4.4]nona-2,7-dienes

A novel series of bicyclic organogermanium derivatives: 5-germaspiro[4.4]nona-2,7-dienes have been prepared by reaction of 1,1-dihalogermacyclopent-3-enes with the appropriate conjugated diene and an alkali metal in a suitable organic solvent. The best results were obtained by using 1,1-dichlorogermacyclopentenes with isoprene or 2,3-dimethylbutadiene and lithium in 5/1 ether/tetrahydrofuran. Except for 2,3,7,8-tetramethyl-5-germaspiro[4.4]nona-2,7-diene, which is crystalline, the 5-germaspirononadienes are colourless liquids, which distil without decomposition under reduced pressure but which slowly polymerize on standing. In the mass spectra of all the spiradienes, the main peak corresponds to the loss of one ring, the less substituted in the case of unsymmetrical molecules. Attempts to obtain 5-germaspiro[4.4]nona-2,7-diene were unsuccessful.     

Resolution of Spiro[4.4]nonane-1,6-dione by Chiral Inclusion Complexation

Becauseoftheintrinsicallyskew0rientationofthebicycIicringsinthespirocyclicdiones,thechiralspiro[4.4]n0nane-l,6-dionemaybeexcel1entprecursorsforusefulligandswhichcanbeusedinmetal-mediatedasymmetricsynthesis(includingasymmetriccatalysis).Recently,werep0rtedasymmetrichydrogenati0nof2-acetamid0acylicacidusingspir0l4.4]n0nane-l,6-di0nederivativesl(0r2)aschiralligandgave>99.9%conversi0nand>99.9%enanti0mericexcess'.Becauseofthepotential0ftheuseof0pticalIypurespir0[4.4]nonane-l,6-di0neasprecurs0rsforu…     

Gold-catalyzed synthesis of bicyclo[4.3.0]nonadiene derivatives via tandem 6-endo-dig/Nazarov cyclization of 1,6-allenynes

Catalytic cyclization of 1,6-allenynes was achieved by AuPPh(3)SbF(6) (5 mol %) in cold CH(2)Cl(2) (0 degrees C, 0.5-4 h) to form bicyclo[4.3.0]nonadiene products; this cyclization proceeded more efficiently for a substrate bearing R = alkyl (yields >70%). We propose a reaction mechanism involving a 6-endo-dig cyclization of Au(I)-pi-alkyne, followed by Nazarov cyclization.     

Organoselenium mediated asymmetric cyclizations. Synthesis of enantiomerically pure 1,6-dioxaspiro[4.4]nonanes

The asymmetric cyclization of 1-hydroxyoct-7-en-4-one, promoted by camphorselenenyl tetrafluoroborate, generated from camphor diselenide and silver tetrafluoroborate in dichloromethane at room temperature, afforded a mixture of two diastereoisomeric E- and two diastereoisomeric Z-2-[(camphorseleno)methyl]-1,6-dioxaspiro[4.4]nonanes. These were separated by medium pressure liquid chromatography and then deselenenylated with triphenyltin hydride and AIBN to give enantiomerically pure 2-methyl-1,6-dioxaspiro[4.4]nonanes. The camphorseleno group was also substituted by an allyl function using allyltributyltin in the presence of AIBN.     

Über die Chiralität der enantiomeren Spiro[4.4]nonan-1,6-dione

Spiro [4.4] nonane-1, 6-dione (III) has been synthesized in optically active form, and the chirality of the enantiomers determined by chemical correlation.     

Synthesis,dimerization, and oligomerization of 5-silaspiro[4.4]non-2-ene

Synthesis of 5-silaspiro[4.4]non-2-ene and its low-temperature anionic polymerization with the ring opening have been accomplished. A dimer and cyclic oligomers with higher degree of polymerization are predominantly formed under the action of BuⁿLi in THF at −78 °C.     

Synthesis and properties of 1,6-dioxaspiro[4.4]nonane and its derivatives (review)

Data on methods of synthesis and the chemical properties of 1,6-dioxaspiro-[4.4]nonane and its derivatives are correlated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1155–1168, September, 1986.     

Promoter-dependent course of the Beckmann rearrangement of stereoisomeric spiro[4.4]nonane-1,6-dione monoximes

Activation of the Beckmann rearrangement of the enantiopure spirocyclic keto oximes (-)-9 and (-)-12 has been initiated with four acidic promoters. In two cases (PPE and PPSE), concerted 1,2 shift of the anti carbon operates exclusively. This is not the case with PPA or Eaton's reagent, although optical activity is fully maintained in these ring expansions as well.     

An efficient synthesis of the 1,6-dioxaspiro[4.4]nonan-2-one motif of the immunosuppressive triterpenoid Phainanoid F

We describe an efficient synthesis of the 1,6-dioxaspiro[4.4]nonan-2-one motif of the immunosuppressive triterpenoid Phainanoid F and its C4 epimer. A furan oxidative spirocyclization for constructing the spiro center was used as the key step. Other important reactions involved Sharpless asymmetric dihydroxylation, Weinreb ketone synthesis and Yamaguchi esterfication. The synthesis was achieved in 11 linear steps with 17.3% overall yield.     

2,3,7,8-Tetraazaspiro[4.4] nonane, 2,3,7,8-tetraazaspiro-[4.4] nona-2,7-diene and derivatives

Synthetic routes to the title compounds ( 4, 12 ) are described. Chiral derivatives of these, 2,7-bis(phenylcarbamoyl)-2,3,7,8-tetraazaspiro[4.4]nonane ( 7 ) and 3,8-dicarbomethoxy-2,3,7,8-tetraazaspiro[4.4]nona-1,6-diene ( 10 ) were prepared. Synthetic routes to diketo derivatives of other tetraazaspiro[4.4]nonanes were explored. 3,3-Dicarbethoxy-1-pyrazoline ( 24 ) and 3,3-dicarbethoxypyrazolidine ( 25 ) were prepared and their reactions with hydrazine examined. Proton and ¹³C nuclear magnetic resonance spectra of new compounds, including some 5-substituted 3-hydroxypyrazoles, are discussed in relation to structure.     

A simple,efficient, two-step synthesis of symmetric 2,7-dialkyl-1,6-dioxaspiro[4.4]nonanes

A two-step synthesis of symmetric 2,7-dialkyl-1,6-dioxaspiro[4.4]nonanes has been achieved by double Michael addition of nitromethane with two moles of enones on Amberlyst A21, followed by in situ reduction with sodium borohydride, then spontaneous spiroketalization of the obtained nitrodiol, by the Nef reaction under acidic conditions, affords the title compounds in good yields.     

A stereoselective synthetic route to 1,6-Dioxaspiro[4.4]non-3-en-2-ones from cyclopropyl alkyl ketones and alpha-ketoesters

[reaction: see text] The SnCl(4)-mediated reactions of cyclopropyl alkyl ketones with alpha-ketoesters afford a novel method for the synthesis of 1,6-dioxaspiro[4.4]non-3-en-2-ones with high stereoselectivities in moderate to good yields. This process is a sequential reaction involving a nucleophilic ring-opening reaction of the cyclopropane by H(2)O, an aldol-type reaction, and a cyclic transesterification mediated by Lewis acid.