Transannular cyclization of the E,E-germacradienolide hanphyllin

The results are reported of the interaction of the trans,trans-germacradienolide hanphyllin with m-chloroperbenzoic acid and with 50% sulfuric acid. This leads to a cyclization reaction with the formation of eudesmanolides: 1β-hydroxy-3-oxo-1,4,5,7α(H),6β(H)-eudesm-11(13)-en-6,12-olide, ridentin B, and 3β-hydroxy-5,7α(H),6β(H)-eudesma-4(15),11(13)-dien-6,12-olide; and also products of the opening of the lactone ring as a consequence of transesterification. The structures of the compounds obtained are discussed on the basis of spectral results (IR, PMR, and mass spectra) and of x-ray structural analysis. Institute of Organic Synthesis and Coal Chemistry, Kazakhstan Academy of Sciences, Karaganda. A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 508–517, September–October, 1992.     

Crystallographic distinction between "contact" and "separated" ion pairs: structural effects on electronic/ESR spectra of alkali-metal nitrobenzenides

The classic nitrobenzene anion-radical (NB(-*) or nitrobenzenide) is isolated for the first time as pure crystalline alkali-metal salts. The deliberate use of the supporting ligands 18-crown-6 and [2.2.2]cryptand allows the selective formation of contact ion pairs designated as (crown)M(+)NB(-*), where M(+) = K(+), Rb(+), and Cs(+), as well as the separated ion pair K(cryptand)(+)NB(-*)-both series of which are structurally characterized by precise low-temperature X-ray crystallography, ESR analysis, and UV-vis spectroscopy. The unusually delocalized structure of NB(-*) in the separated ion pair follows from the drastically shortened N-C bond and marked quinonoidal distortion of the benzenoid ring to signify complete (95%) electronic conjugation with the nitro substituent. On the other hand, the formation of contact ion pairs results in the substantial decrease of electronic conjugation in inverse order with cation size (K(+) > Rb(+)) owing to increased localization of negative charge from partial (NO(2)) bonding to the alkali-metal cation. Such a loss in electronic conjugation (or reverse charge transfer) may be counterintuitive, but it is in agreement with the distribution of odd-electron spin electron density from the ESR data and with the hypsochromic shift of the characteristic absorption band in the electronic spectra. Most importantly, this crystallographic study underscores the importance of ion-pair structure on the intrinsic property (and thus reactivity) of the component ions-as focused here on the nitrobenzenide anion.     

O-Tosylaminobenzaldehyde aminals in the synthesis of 1,3-disubstituted propargylamines,derivatives of 3H-2-vinylidene-3-aminoindoline and quinoline

o-Tosylaminobenzaldehyde aminals react with propargyl alcohol and its phenyl ether on heating in acetonitrile in the presence of CuI to yield 3H-2-vinylidene-3-aminoindoline derivatives. Analogous reactions with phenylacetylene and dimethylethynylcarbinol result in 1,3-disubstituted propargylamines. The possibility of using the latter compounds in synthesis of quinoline derivatives was shown: cyclization of 1-(o-tosylaminophenyl)-1-morpholino-3-phenylprop-2-yne in the presence of H₂SO₄ and KOH gave 2-phenylquinoline and 2-phenyl-4-morpholinoquinoline, respectively. 3H-2-Phenoxymethylvinylidene-3-morpholinoindoline was studied by X-ray diffraction spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2236–2240, November. 1995.     

Synthesis,and crystal and molecular structures of anabasinium O,O-dialkyl phosphorothioates

The synthesis has been effected of anabasinium O,O-dialkyl phosphorothioates. The crystal and molecular structures of the complex compounds obtained have been determined by the method of x-ray structural analysis. It has been established that the cations and anions of the anabasinium O,O-dialkyl phosphorothioates are combined into cyclic associates each including two anions and two cations with different conformations.Institute of Organic Synthesis and Coal Chemistry, Academy of Sciences of the Kazakh SSR. A. N. Nesmayanov Institute of Organometallic Compounds, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 500–505, July–August, 1990.     

Effect of substituents at atoms of double bonds on the conformation of the 1,3-cyclohexadiene ring

The effect of alkyl substituents at atoms of double bonds on the conformation of the 1,3-cyclohexadiene ring was studied using a molecular-mechanics method. It was shown that the introduction of substituents results only in a change of the degree of ring puckering. It is concluded that there is equilibrium between flattening and unflattening factors, which then governs the constancy of the ring conformation.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 4, pp. 334–337, July–August, 1992.     

Conformations of the rings and relative stabilities of isomers of trans,trans- and trans,cis-eudesman-8,12-olides

A series of isomers of trans,trans- and trans,cis-eudesman-8,12-olides has been investigated by the method of molecular mechanics (MMM). Questions of the energetic suitability of particular isomers, of the influence of the orientation of substituents attached to the basic skeleton on their conformation, and of the relative stabilities of the conformers with different methods of linking the rings are considered. A. N. Nesmeyanov Institute of Heteroorganic Compounds, USSR Academy of Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 334–338, May–June, 1990.     

Imine-enamine tautomerism of dihydroazolopyrimidines. 3. 5-Aryl-substituted 4,7(6,7)-dihydro-1,2,4-triazolo[1,5-a]pyrimidines

5-Aryl-substituted 4,7(6,7)-dihydro-1,2,4-triazolo[1,5-a]pyrimidines were obtained by condensation of 3-amino-1,2,4-triazole with -dimethylaminopropiophenone hydrochlorides or crotophenone. The effect of steric and electronic factors on the position of the imine-enamine equilibrium in solutions of the synthesized substances is examined. 5-Phenyl-4,7-dihydro-1,2,4-triazolo[1,5-a]pyriniidine was subjected to x-ray diffraction analysis.See [1] for Communication 2.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1539–1544, November, 1991.     

Diels-Alder topochemistry via charge-transfer crystals: novel (thermal) single-crystal-to-single-crystal transformations

The solid-state [4+2] cycloaddition of anthracene to bis(N-ethylimino)-1,4-dithiin occurs via a unique single-phase topochemical reaction in the intermolecular (1:1) charge-transfer crystal. The thermal heteromolecular solid-state condensation involves the entire crystal, and this rare crystalline event follows topochemical control during the entire cycloaddition. As a result, a new crystalline modification of the Diels-Alder product is formed with a crystal-packing similar to that of the starting charge-transfer crystal but very different from that of the (thermodynamically favored) product modification obtained from solution-phase crystallization. Such a single-phase transformation is readily monitored by X-ray crystallography at various conversion stages, and the temporal changes in crystallographic parameters are correlated with temperature-dependent (solid-state) kinetic data that are obtained by 1H NMR spectroscopy at various reaction times. Thus, an acceleration of the solid-state reaction over time is found which results from a progressive lowering of the activation barrier for cycloaddition in a single crystal as it slowly and homogeneously converts from the reactant to the product lattice.     

Molecular and crystal structure of the germacranolide argolide from Artemisia glabella

The new germacranolide argolide has been isolated from the epigeal part ofArtemisia glabella, and its structure has been shown by its conversion into oxopelenolide B. From the results of an x-ray investigation it is suggested that argolide has the spatial structure of 3-oxo-4,7,6(H)-germacra-1(10),11(13)-dien-6,12-olide.Institute of Organic Synthesis and Coal Chemistry, Kazakh Academy of Sciences, Karaganda. A. N. Nesmeyanov Institute of Organometallic Chemistry, Russian Academy of Sciences, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 653–657, September–October, 1991.