The electron impact induced fragmentations of some 7-alkyl-3-oxabicyclo[3.3.1]nonanes

The mass spectra of a series of 7-alkyl substituted 3-oxabicyclo[3.3.1]nonanes are recorded. The fragmentation has been studied by the use of the metastable DADI and defocussing techniques. The character of the alkyl group is found to influence the fragmentation pattern. Stereoselective fragmentations for the 7-t-butyl derivatives are observed. In the endo-isomer, in contrast to the exo-isomer, a transannular hydrogen transfer plays a role.     

Organoboron compounds: CDIV. A hydride transfer reacton in the series of ate complexes of 7-substituted 3-alkyl-3-borabicyclo[3.3.1]nonanes and 3-alkyl-3-borabicyclo[3.3.1]non-6-enes

The ate complexes of 7-substituted 3-alkyl-3-borabicyclo[3.3.1]nonanes and of 3-alkyl-3-borabicyclo[3.3.1]non-6-enes react with acetyl chloride under mild conditions by an intermolecular β-hydride transfer mechanism to form 5-substituted 3-methylenecyclohex-1-ylmethyl(dialkyl)boranes. The latter compounds were converted, by oxidation with alkaline hydrogen peroxide, to 3-substituted 1-methylene-5-hydroxymethylcyclohexanes. The reaction of cycloalkylmethyl(dialkyl)boranes with aromatic aldehydes was applied to the synthesis of 1,3-di- and 1,3,5-tri-methylene derivatives of the cyclohexane series.     

Sigmatropic [1,3]-boron shift (permanent allylic rearrangement) in 3-allyl-3-borabicyclo[3.3.1]nonanes

2D ¹H-¹H EXSY NMR spectroscopy show that the free energy of activation ΔG ^≠ in six 3-allyl-3-borabicyclo[3.3.1]nonane derivatives is significantly higher (72–86 kJ mol^?1) than that in typical allylboranes (48–66 kJ mol^?1). For the first member of the series, viz., 3-allyl-3-borabicyclo[3.3.1]nonane, the activation parameters of the permanent allylic rearrangement were also determined (ΔH ^≠ = 82.7±3.4 kJ mol^?1, ΔS ^≠ = ?11.8±10.3 J mol^?1 K^?1, E _A = 85.5±3.4 kJ mol^?1, lnA = 29.2±1.2).     

Organosilicon chalcogenides with trisilane units - bicyclo[3.3.1]nonanes, bicyclo[3.2.2]nonanes and spiro[4.4]nonanes

Treatment of 1,2,3-trichloropentamethyltrisilane (1) with H₂S/NEt₃ results in the formation of a mixture of two isomers of (Me₅Si₃)₂S₃ with a bicyclo[3.3.1]nonane (2a) and a bicyclo[3.2.2]nonane (2b) skeleton, while the reaction of 1 with Li₂Se yields one product only, (Me₅Si₃)₂Se₃ (3a), with a bicyclo[3.3.1]nonane structure. Besides ¹H, ¹³C, ²⁹Si and ⁷⁷Se NMR spectroscopy 3a has also been characterized by a crystal structure analysis.Compounds Si(SiMe₂EMR₂E)₂ (5a-h: MR₂: SiMe₂ (5a, c, d), SiPh₂ (5b), GeMe₂ (5e, f), SnMe₂ (5g, h); E=S (5a, b, e, g), Se (5c, f, h), Te (5d)) with a spiro[4.4]nonane skeleton have been obtained in mixture with varying amounts of the corresponding six-membered rings (R₂ME)₃ by reactions of mixtures of 1,2,2,3-tetrachlorotetramethyltrisilane (4) and diorganodichlorosilanes, Me₂GeCl₂ or Me₂SnCl₂, with H₂S/NEt₃, Li₂Se or Li₂Te and have been characterized in situ by multinuclear NMR spectroscopy (¹H, ¹³C, ²⁹Si, ¹¹⁹Sn, ⁷⁷Se, ¹²⁵Te) and GC-MS.     

Conformational analysis of 3-borabicyclo[3.3.1]nonane derivatives

Conformations of 3-borabicyclo[3.3.1]nonane derivatives have been studied by means of ¹H and ¹³C NMR spectroscopy. With the aid of the coupling constants ³J(HH) and ¹³C chemical shifts it has been shown that all the derivatives of 3-borabicyclo[3.3.1]nonane with the trigonal boron atom studied are in a flattened double-chair conformation. In 3-borabicyclo[3.3.1]nonane derivatives with the tetra-coordinated boron atom and substituents at the 7α-position, the chair-boat conformation predominates, the boat conformation being characteristic of the cyclohexane ring; exceptions are the compounds with the internal donor—acceptor bond between the boron atom an 7α-substituent.     

Conformational behavior of 3-borabicyclo[3.3.1]nonanes: 1. Study of molecular dynamics in 3-methoxy-7α-phenyl-1,5-dimethyl-3-borabicyclo[3.3.1]nonane

3-Methoxy-7α-phenyl-1,5-dimethyl-3-borabicyclo[3.3.1]nonane 5 in solution at room temperature exists in the double chair conformation, as shown by NMR studies. Increasing the temperature leads to an increase in the population of the chair–boat conformation. At decreased temperature hindered rotation around the B---O bond is observed for 5. Dissolving 5 in deuteropyridine leads to the reversible formation of complex 6, which exists in the chair–boat conformation. The chair–boat conformation is also the most stable one for chelate compound 7 with a tetracoordinated boron atom.     

Synthesis and conformational analysis of exo-and endo-7-substituted-3-azabicyclo[3.3.1]nonanes

The synthesis of some 7-substituted-3-azabicyclo[3.3.1]nonanes is described. Routes followed were the debenzoylation of the 7-benzoyl derivative 7 and the decarboxylation of the 7-carboxy compounds 21 and 27. The so-obtained 7-oxo-N-tosyl-3-azabicyclo[3.3.1]nonanes 8and 11 show an extremely low reactivity towards a series of nucleophilic reagents. From analysis of the ¹H NMR spectral data of a series of derivatives, the twin-chain conformation for the 7-exo compounds and the chair-boat conformation for the 7-endo compounds is indicated.     

The mass-spectral fragmentation of bicyclo[3.3.1]nonanes

The mass spectra of twelve bicyclo[3.3.1]nonanes have been recorded. The high number of metastables observed, exact mass measurements of the ions and low ionising voltage spectra, permitted the rationalisation of most of the fragmentation pathways. The 1-phenyl substituent triggers the major fragmentation in the hydrocarbon, whereas it has minor influence in the oxygenated compounds. Significant differences in the abundance of [M ? H₂O]⁺ ions for stereoisomeric alcohols of this series have been observed.     

Synthesis and Transformations of 1,3,5,7-Tetraazabicyclo[3.3.1]nonanes

Published data on the synthesis of 3,5-disubstituted 1,3,5,7-tetraazabicyclo[3.3.1]nonanes and their transformations into 1,3,5,7-tetraazacyclooctanes and 1,3,5-triazacyclohexanes are discussed.     

Complexation properties of 3,7-diazabicyclo[3.3.1]nonanes

The electrochemical behavior of some 3,7-diazabicyclo[3.3.1]nonanes and their complexes with copper(II) chloride was investigated. The composition and stability of complexes are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 456–458, March, 1995.     

3,7-disubstituted bicyclo [3.3.1] nonanes—II : Synthesis and conformation of some 3,7-disubstituted 9-oxobicyclo [3.3.1] nonanes

Condensation of pyrrolidine enamines of 4-alkylcyclohexanones with methyl α-(bromomethyl)acrylate affords methyl 7β- and 7α-alkyl-9-oxobicyclo [3.3.1] nonane-3α-carboxylates in a ratio of 3:2. The mechanism of the annelation reaction is discussed. The conformations of the reaction products and their epimers have been studied by means of PMR spectroscopy.     

The chemistry of piperidines—I : 3-Azabicyclo[3.3.1]nonanes

The reaction of pyrrolidine, piperidine and morpholine enamines of 1-methyl-4-piperidone with acraldehyde is found to be a convenient route to 3-aza-3-methyl-6-cycloalkylaminobicyclo[3.3.1]-nonan-9-ones. In each case two difficultly separable ketones are obtained which on reduction give mixtures of isomeric alcohols. The alcohols are separated and their stereochemistries are determined from their physical and chemical properties.     

Synthesis of pyrazole- and thiazole-annulated 3-R-1,5-dinitro-3-azabicyclo[3.3.1]nonanes

The previously unknown 3-R-1,5-dinitro-3-azabicyclo[3.3.1]nonanes fused to the pyrazole or thiazole rings were synthesized by the reductive cyclization of m-dinitroindazoles and benzothiazoles. The method is based on the reduction of carbon-carbon bonds in the benzene ring, which are activated by the meta-nitro groups, with NaBH₄ followed by the Mannich reaction with formaldehyde and primary amines.     

Synthesis of 3-R-1,5-dinitro-3-azabicyclo[3.3.1]nonanes fused to azoles

3-R-1,5-Dinitro-3-azabicyclo[3.3.1]nonanes fused to the pyrazole, thiazole, and triazole rings were synthesized by reductive cyclization of meta-dinitrobenzazoles.     

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.     

13C NMR spectroscopy of some 3- and 7-substituted bicyclo[3.3.1]nonanes

The ¹³C NMR spectra of a series of 3,7-substituted bicyclo[3.3.1]nonane derivatives are examined. Taken into account substituent influences, the ¹³C chemical shifts appear to be diagnostic for the conformation of the bicyclo[3.3.1]nonane derivative.