Synthesis and conformation of some 2,4-dioxa- and 2,4-dioxa-3-silabicyclo[3.3.1]nonanes

The conformation of the title compounds established by ¹³C and ¹H NMR spectroscopy shows that replacement of the 2- and 4-methylene groups in bicyclo[3.3.1]nonane by ether oxygen atoms strongly destablizes the cc conformation: in 2-oxabicyclo[3.3.1]-nonane the cc and the bc conformers are about equally populated, whereas in 2,4-dioxabicyclo[3.3.1]nonane the bc conformation predominates. The 2,4-dioxa-3-silabicyclo[3.3.1]nonanes also occur predominantly inthe bc conformation. As in the carbocyclic bicyclo[3.3.1]nonanes both wings are strongly flattened. A stereoselective synthesis of 3-methylbicyclo[3.3.1]nonane, an important model compound in this study, is described.     

Efficient Synthesis of a New Family of 2,6-Disulfanyl-9-selenabicyclo[3.3.1]nonanes

The efficient synthesis of a new family of 2,6-disulfanyl-9-selenabicyclo[3.3.1]nonanes in high yields has been developed based on 9-selenabicyclo[3.3.1]nonane-2,6-dithiolate anion generated from bis-isothiouronium salt of 2,6-dibromo-9-selenabicyclo[3.3.1]nonane. The derivatives of 2,6-disulfanyl-9-selenabicyclo[3.3.1]nonane containing alkyl, allyl and benzyl moieties have been prepared in 90–99% yields by nucleophilic substitution of 9-selenabicyclo[3.3.1]nonane-2,6-dithiolate anion with alkyl, allyl and benzyl halides. The reaction of nucleophilic addition of 9-selenabicyclo[3.3.1]nonane-2,6-dithiolate anion to alkyl propiolates afforded 2,6-di(vinylsulfanyl)-9-selenabicyclo[3.3.1]nonanes. The conditions for regio- and stereoselective addition of 9-selenabicyclo[3.3.1]nonane-2,6-dithiolate anion to a triple bond of alkyl propiolates have been found. To date, not a single representative of 2,6-disulfanyl-9-selenabicyclo[3.3.1]nonanes has been described in the literature.     

The "hockey sticks" effect revisited: the conformational and electronic properties of 3,7-dithia-1,5-diazabicyclo[3.3.1]nonane from the QTAIM perspective

The conformational effects in bicyclo[3.3.1]nonanes, while thoroughly studied, have not yet received the full theoretical explanation. R. F. W. Bader's quantum theory of atoms in molecules presents unique opportunities for studying the stereoelectronic interactions (SEI) and weak intramolecular bonding leading to these effects. Here, we report the study of 3,7-dithia-1,5-diazabicyclo[3.3.1]nonane by means of the topological analysis of the calculated (MP2(full)/6-311++G**) and experimental (X-ray derived) charge density to reveal the origins of the so-called "hockey sticks" effect observed in similar compounds. A new explanation of the relative stability of bicyclo[3.3.1]nonane conformers based on the analysis of the QTAIM atomic energies is given. The H···H and S···S interactions in bicyclo[3.3.1]nonane and its dithia derivatives are shown to be significant factors contributing to the differences in the relative stability of the conformers.     

One-pot conversion of carboxylic acids to aldehydes through treatment of acyloxy-9-borabicyclo[3.3.1]nonanes with lithium 9-boratabicyclo[3.3.1]nonane

Carboxylic acids are readily reduced to the corresponding aldehydes in high yields by treatment of acyloxy-9-borabicyclo[3.3.1]nonanes with lithium 9-boratabicyclo[3.3.1]nonane (Li 9-BBNH) at room temperature.     

Electrophilic Additions to Strained Bridgehead Olefins. Estimation of Strain by Comparison with the Solvolysis of Bridgehead Bromides

The addition of water, acetic acid, and hydrogen bromide to the strained bridge-head olefins bicyclo[3.3.1]-1(2)-nonene (1) , bicyclo[4.2.1]-1(8)-nonene (2) , and bicyclo[4.2.1]-1(2)-nonene (3) gives exclusively the bridgehead alcohols, acetates, and bromides, respectively. The reaction rate constants for the addition of acetic acid to the bridgehead olefins 1,2 and 3 , and the solvolysis rates for the related 1-bromo-bicyclo[3.3.1]nonane (4) and 1-bromobicyclo[4.2.1]nonane (5) were measured. A comparison of the activation enthalpies of these two reactions gives an estimate of relative strain of the bridgehead double bond. The strain in the bicyclo[4.2.1]nonenes 2 and 3 is similar to that in trans-cyclooctene (8-9 kcal/mol).     

Lone pairs vs. covalent bonds: conformational effects in bicyclo[3.3.1]nonane derivatives

Structural Chemistry - Investigations on the relative energy of two least-strain conformers for bicyclo[3.3.1]nonane 1, bicyclo[3.3.1]nonan-9-one 2, and their heteroanalogues:...     

Syntheses of bicyclic 1,2-diols via the ring-expansion of bridgehead aldehydes of bicyclo[3.2.1]octane and bicyclononanes with benzoyl triflate

Bridgehead aldehydes of bicyclo[3.2.] loctane (11a), bicycio-[3.3.1]nonane (12a), and bicyclo[3.2.2]nonane (13a) have been subjected toacylative ring-expansion by using benzoyl trifluoromethanesulfonate (trif-late) to give mixtures of two or three bicyclic 1,2-diol monobenzoates containing the hydroxyl group on the bridgehead carbon. Control experiments have shown that the reaction is kinetically controlled. The direction of the ring-expansion has been found to be predictable by comparing the strain energies calculated by molecular mechanics of the parent hydrocarbons corresponding to the produced diol monobenzoates. The major monobenzoates, easily isolated in practical yields by crystallization or column chromatography, have been converted to the corresponding diols, and their structures determined. For synthetic purposes, 11a gives bicyclo[3.3.1]nonane-1,endo-2-diol (27), and 12a the endo and exo isomers of bicyclo[4.3.1]decane-1,2-diol (33 and 35, respectively). From 13a is furnished bicyclo[4.2.2]decane-1,2-diol (42). Diols 27, 33. and 42 are conveniently oxidized to the corresponding ketols by using silver carbonate in 50 – 80% yields. The oxidation of diol 35 to 1-hydroxybicyclo[4.3.1]decan-2-one (34) failed under similar conditions, but it was achieved by the Corey oxidation by using dimethylsulfide -chlorine complex.     

Solvolysis of 2-Bicyclo

The solvolysis rate of 2-bicyclo[3.2.2]nonyl p-toluenesulfonate (6-OTs) was nearly equal to that of cycloheptyl p-toluenesulfonate in 2,2,2-trifluoroethanol (TFE). This indicates that the ethylene bridge in 6-OTs does not significantly enhance the rate and that 6-OTs ionizes without anchimeric assistance. The solvolysis of [1-(13)C]-2-bicyclo[3.2.2]nonyl p-toluenesulfonate in methanol or TFE gave 2-substituted bicyclo[3.2.2]nonane, exo-2-substituted bicyclo[3.3.1]nonane, 2-bicyclo[3.2.2]nonene (10), and 2-bicyclo[3.3.1]nonene (11), whose distributions of (13)C labels were determined by quantitative (13)C NMR analysis using a relaxation reagent. The (13)C labels were exclusively placed at only two positions, the ratios of them were not unity, and the labels in 10 were less extensively scrambled than those in other products. These results indicate that the 2-bicyclo[3.2.2]nonyl cation is classical and that 10 is formed at a former ionization stage than 2-substituted bicyclo[3.2.2]nonane. The (13)C redistributions for both exo-2-substituted bicyclo[3.3.1]nonane and 11, which are yielded via 1,3-hydride shift, were similar to that of 2-substituted bicyclo[3.2.2]nonane, suggesting that 1,3-hydride shift occurs mainly at the solvent-separated ion pair.     

Chair-boat equilibria in bicyclo[3.3.1]nonane and some 3- and 3,7-substituted derivatives: Thermodynamic parameters and geometry of the conformers as obtained by molecular mechanics

ΔG-Values for conformational equilibria in 3,7-substituted bicyclo[3.3.1]nonanes have been obtained by means of epimerisation experiments (cc α bc) and by variable temperature ¹³C NMR (bc α bb). The results of these experiments fit well with those of molecular mechanics using the Schleyer force field. In bicyclo[3.3.1]nonane and 3β-substituted derivatives the cc conformation predominates; however, the bulky 3β-substituent t-butyl, is found to have a destabilizing effect. A 3α-substituent forces the substituted wing into the boat conformation. For the 3α,7α-substituted derivatives the conformational preferences depend on the size of the substituents: for 3α-methyl-7α-t-butylbicyclo[3.3.1]nonane the cb and t-bb conformers are of approximately equal enthalpy. The geometries, obtained by the calculations, show that the conformers of bicyclo[3.3.1]nonane (cc, bc and t-bb) are all distinctly flattened. The boat wings of bc conformers are not twisted to any extent. The t-bb is the most stable bb conformation. The influence of substitution at positions 3 or 7 is discussed in detail; in general, a bulky substituent such as t-butyl, affects the geometry of both wings of the ring system. The calculated geometries are in good agreement with the conclusions of previous ¹H NMR investigations.     

5-Hydroxy-1-phosphabicyclo[3.3.1]nonan

5-Hydroxy-1-phosphabicyclo[3.3.1]nonane A new approach to 1-phosphabicyclo[3.3.1]nonane compounds involves free-radical cyclization of 4-trimethylsilyloxy-4-phosphinomethyl-hepta-1.6-diene synthesized by the reaction of 2.2-diallyl-oxirane with KPH₂ followed by trimethylsilylation. Trimethylsilyl groups are easily cleaved in boiling methanol forming 5-hydroxy-1-phosphabicyclo[3.3.1]nonanes. Silylated and desilylated bicyclic compounds are characterized by n.m.r. and i.r. data.     

3,7-disubstituted bicyclo[3.3.1]nonanes—III: Synthesis and conformation of bicyclo[3.3.1]nonane-3α,7α-dicarboxylic acid,its dimethyl ester and some other 3,7-disubstituted bicyclo[3.3.1]nonanes; adamantane as an integrated holding system

The conformation of bicyclo[3.3.1]nonane-3α,7α-dicarboxylic acid and its dimethyl ester has been studied by comparing ¹H NMR and ¹³C NMR spectra of these compounds with those of some model 3,7-disubstituted bicyclo[3.3.1]nonanes, fixed in a single conformation by the use of adamantane as an integrated holding group or by means of suitable substitution. It is shown that the dicarboxylic acid and its dimethyl ester exist predominantly as two rapidly interconverting (identical) chair-boat conformations with distinctly flattened rings; the population of the double-boat conformation appears to be very small.     

Substituierte 9-Oxabicyclo[4.2.1]- und 9-Oxabicyclo[3.3.1]nonane IV. endo,endo-2,5-Dihydroxy-9-oxabicyclo[4.2.1]nonan,endo, endo-, endo,exo- und exo,exo-2,6-Dihydroxy sowie endo,exo-2,7-Dihydroxy-9-oxabicyclo[3.3.1]nonan; Darstellung und Umwandlungsprodukte

The synthesis of the following compounds and reaction products thereof are described: endo, endo-2,5-dihydroxy-9-oxabicyclo[4.2.1]nonane ( 3–5 ), epimeric 2,6-dihydroxy-9-oxabicyclo[3.3.1]nonanes (endo, endo: 6–8 , exo, exo: 29–32 , and endo, exo: 43–45 ), and endo, exo 2,7-dihydroxy-9-oxabicyclo[3.3.1]nonane ( 46–50 ).     

Scope and applications of second generation palladium-catalyzed cycloalkenylation. Stereoselective total syntheses of isoiridomyrmecin, isodihydronepetalactone, and α-skytanthine

Functionalized bicyclo[3.2.1]octanes, -oxabicyclo-[4.3.0]nonanes, 3-azabicyclo[3.3.0]octanes, and 3-azabicyclo[4.3.0]nonanes were easily synthesized via a second generation palladium-catalyzed cycloalkenylation. Isoiridomyrmecin and isodihydronepetalactone, both of which feature a 3-oxabicyclo[4.3.0]nonane subunit, were stereoselectively synthesized via a second generation palladium-catalyzed cycloalkenylation as the key step. α-Skytanthine, a typical 3-azabicyclo[4.3.0]nonane alkaloid, was also constructed using the same catalytic cyclization protocol.     

Construction of the adamantane core of plukenetione-type polycyclic polyprenylated acylphloroglucinols

The construction of a highly functionalized adamantane core of plukenetione-type polycyclic polyprenylated acylphloroglucinols (PPAPs) is described. The method features the construction of the bicyclo[3.3.1]nonane core (3) by successive Michael reactions and the construction of the adamantane core of plukenetione-type PPAPs by acid-catalyzed cyclization of a bicyclo[3.3.1]nonane precursor (2).     

Formation of Isomeric 3-Azabicyclo[3.3.1]nonanes in a Reaction of 1-(2-Hydroxyethoxy)-2,4-dinitrobenzene with Sodium Borohydride,Formaldehyde, and Methylamine

Anionic hydride adduct of 1-(2-hydroxyethoxy)-2,4-dinitrobenzene was brought into a double Mannich condensation with formaldehyde and methylamine to furnish a mixture of isomeric 3-azabicyclo[3.3.1]nonanes: 3-methyl-6-(2-hydroxyethoxy)-1,5-dinitro-3-azabicyclo[3.3.1]non-6-ene and 3-methyl-6,6-ethylenedioxy-1,7-dinitro-3-azabicyclo[3.3.1]nonane. By means of NMR spectroscopy, X-ray difraction analysis, and quantum chemistry (PM3) we demonstrated that the spirocyclic isomer had chair-chair conformation with diequatorial orientation of substituents in positions 3 and 7.     

Synthesis and study on 2,4,6,8-tetraaryl- 3,7-diazabicyclo[3.3.1]nonanes and their derivatives

1-Carbethoxy-2,4,6,8-tetraaryl-3,7-diazabicyclo[3.3.1] nonan-9-ones (1, 2) were synthesized and their 1H and 13C NMR data are reported. Chemical shifts and spectral assignments for 2,4,6,8-tetrakis(4-chlorophenyl)-3,7-diazabicyclo[3.3.1]nonan-9-one (3), 2,4,6,8-tetraphenyl-3-thia-7-azabicyclo[3.3.1]nonan-9-one (4) and 2,4,6,8-tetraaryl-3,7-diazabicyclo[3.3.1]nonanes (5-7) are also included.     

Reaction of α,β-unsaturated trifluoromethyl ketones with cyclic enamines

The reactions of ,-unsaturated trifluoromethyl ketones containing aromatic and heteroaromatic substituents with 1-morpholinocyclopentene, 1-morpholinocyclohexene, and 1-methyl-4-morpholino-1,2,5,6-tetrahydropyridine were studied. The reactions proceeded stereospecifically to give the corresponding bicyclo[3.2.1]octane, bicyclo[3.3.1]nonane, and azabicyclo[3.3.1]nonane derivatives.     

Syntheses and conversion of polyhedral compounds. 26. Synthesis of new heteropolyhedral compounds by heterocyclization of certain 3,7-disubstituted derivatives of 3,7-diaza-and 1,3,7-triazabicyclo-[3.3.1]nonanes

The following heterocyclization reactions have been carried out: heterocyclization of 3,7-diacryloyl-3,7-diazabicyclo[3.3.1]nonane by benzylamine, heterocyclization of 3,7-diacryloyl-, 3,7-bis(-bromopropionyl)-, and 3,7-bis(-chloroethyl)-3,7-diazabicyclo[3.3.1]nonanes by hydrogen sulfide, and heterocyclization of 3,7-bis(bromoacetyl)- and 3,7-diacryloyl-1,3,7-triazabicyclo[3.3.1]nonanes by benzylamine and hydrogen sulfide. New compounds were obtained, based on previously unknown thiadiaza-, triaza-, and tetraazatricyclic systems.For Communication 25, see [1].A. L. Mndzhoyan Institute of Fine Organic Chemistry, National Academy of Sciences of the Republic of Armenia, Erevan 375014. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1133–1136, August, 1998.     

Synthesis of indoles condensed with a bicyclo[3.3.1]nonane skeleton

Derivatives of mono- and bisindoles condensed with a bicyclo[3.3.1]nonane skeleton were synthesized from bicyclo[3.3.1]nonane-2,6-dione and 6-hydroxybicyclo[3.3.1]nonan-2-one by means of the Fischer reaction.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 315–318, March, 1979.     

2-Oxo-9C(3)-hydroxy- und 2-Oxo-9C(7)-hydroxy-bicyclo[3.3.1]nonan

A synthesis of the two C(9) epimers 14 and 15 of 2-oxo-9-hydroxy-bicyclo[3.3.1]nonane is described starting from the two C(2) epimers 3 and 4 of 2-hydroxy-9-oxo-bicyclo[3.3.1]nonane.