Thermodynamic quantities for the acid dissociation of alkylammonium ions in water over a wide temperature range

Enthalpies of protonation in aqueous solution have been determined from calorimetric measurements between 0 and 100°C for methylpentylamine, butyldimethylamine, and quinuclidine; between 0 and 125°C for di-iso-propylamine; and between 0 and 75°C for 1-azacycloheptane. Values ofpK_a at 25°C have been determined from pH measurements using a glass electrode for di-iso-propyl-, methylpentyl-, and butyldimethylamine. The calorimetric results are used together with values ofpK_a at 25°C to derive expressions which allow the calculation of accuratepK_a values over a large temperature range. The heat capacity and entropy changes for the protonation of aqueous alkylamines found in the present and in previous studies are discussed in terms of differences in hydrophobic solvation of the alkyl groups in the neutral amines and the ions.     

Molecular structure of AlH3[N(CH2CH2)3CH]2

Reaction of AlH₃[N(CH₂CH₂)₃CH] with hexamethyltrisiloxane, (OSiMe₂)₃, gives rise to the bis-quinuclidine complex AlH₃[N(CH₂CH₂)₃CH]₂, which has been characterized by ¹H and ¹³C NMR spectroscopy and X-ray crystallography. The molecular structure of AlH₃[N(CH₂CH₂)₃CH]₂ consists of a trigonal bipyramidal aluminum with axial coordination of the quinuclidine ligands. Crystal data: orthorhombic, space group Pbcn, a = 10.6895(9), b = 12.266(1), c = 12.3794(9) Å, V = 1623.2(2) ų, and Z = 4.     

Molecular structures of quinuclidinic neurokinin antagonists: 2-(2-Phenylbenzylidene)-3-(2-X-benzylamino) derivatives

The solid-state molecular conformations and crystal structures of three analogues of the CP-96,345 molecule, an important nonpeptidic SP antagonist, namely the (±)-2-(3-phenylbenzilidene)-3-(2-benzylamino) quinuclidine, theo-chloro- and theo-methoxy-derivatives, have been determined by X-ray diffusion analyses and refined to finalR values of 0.055, 0.045, and 0.056, respectively. All three molecules in the solid state show the same disposition of the substituents of the double bond and differences in the conformation mainly caused by the need of releasing intramolecular strains and/or nonbonded interactions. The observed molecular structures are compared to the reported solid-state structure of the CP-96,345 and correlated to the biological activity as NK antagonists.     

Quinuclidine-Thiourea Inclusion Compound. A Perfect van der Waals Cavity

Thiourea reacts with 1-azabicyclo[2.2.2]octane (quinuclidine, Q) in methanol at room temperature leading to the formation of Q(3-thiourea).Single crystal X-ray diffraction analysis shows that the product has a rhombohedral structure, = = 90°, = 120°,a = b = 15.9371(2),c = 12.4248(2),which may bedescribed as a thiourea matrix defining hexagonal channels where the quinuclidine molecules are located. The ¹³C-cross polarisation magic angle spinning (CP-MAS) study indicates that the guest inside the cavities has high conformational, rotational and translational mobility at room temperature. Thermal studies indicate that the structural identity of the thiourea matrix remains after a partial loss of amine, and this result suggests that the thiourea-amine inclusion compound possesses an open host structure, or that a topotactic process is associated.     

Synthesis of biologically active compounds based on 2-ferrocenylmethylene-3-quinuclidone

Biologically active nitrogen heterocycles (1–7) containing ferrocene and quinuclidine fragments were synthesized. 3-Methylene-2-ferrocenylmethylenequinuiclidine forms adducts withN-phenylimides of azodicarboxylic (the structure was established by X-ray structural analysis) and malefic acids. 3-Methylene-2-fer-rocenylmethylenequinticlidine also undergoes [4+2]-cyclodimerization when heated and adds salts of the 3-methyl-2-ferrocenylmethyleneI-azoniabicyclo[2.2.2]oct-3-yl cation at the terminal methylene group to form a linear addition product.Instituto de Quimica, Universidad Nacional Autonoma de Mexico (UNAM), Circuito Exterior, Ciudad Universitaria, Coyoacan.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp 2743–2750, November, 1996.     

Three new quinuclidine‐based structures: second harmonic generation response for 1,2‐bis(1‐azoniabicyclo[2.2.2]octan‐3‐ylidene)hydrazine dichloride

The crystal structures of three quinuclidine‐based compounds, namely (1‐azabicyclo[2.2.2]octan‐3‐ylidene)hydrazine monohydrate, C₇H₁₃N₃·H₂O ( 1 ), 1,2‐bis(1‐azabicyclo[2.2.2]octan‐3‐ylidene)hydrazine, C₁₄H₂₂N₄ ( 2 ), and 1,2‐bis(1‐azoniabicyclo[2.2.2]octan‐3‐ylidene)hydrazine dichloride, C₁₄H₂₄N₄²⁺·2Cl^? ( 3 ), are reported. In the crystal structure of 1 , the quinuclidine‐substituted hydrazine and water molecules are linked through N—H…O and O—H…N hydrogen bonds, forming a two‐dimensional array. The compound crystallizes in the centrosymmetric space group P2₁/c. Compound 2 was refined in the space group Pccn and exhibits no hydrogen bonding. However, its hydrochloride form 3 crystallizes in the noncentrosymmetric space group Pc. It shows a three‐dimensional network structure via intermolecular hydrogen bonding (N—H…C and N/C—H…Cl). Compound 3 , with its acentric structure, shows strong second harmonic activity.     

Solid-state structure and conformation of (Z)-2-(phenylbenzylidene)-3-quinuclidinone,an intermediate in the synthesis of quinuclidine derivatives

(Z)-2-(2-phenylbenzylidene)-3-quinuclidinone, C₂₀H₁₉NO,M _r =300.47D crystallizes in the monoclinicP2₁/c space group witha = 6.9809(2) Å,b=19.0523(2) Å,c = 11.7733(1) Å,=100.92(2)°,V=1537.5(3) ų,Z=4,D _c = 1.298 g/cm³,D _x =1.29 g/cm³ (flotation). Diffractometric data, using CuK radiation,=1.54178 Å, were collected on plate-like crystals. The structure, solved by direct methods was refined to a final R value of 0.037 for the 2645 observed reflections withF _o >3.0(F _o ). The molecule shows a trans conformation around the double bond. The quinuclidine and the diphenyl moieties present deformations in their geometric and conformational parameters due to the need of releasing intramolecular strains and/or nonbonded interactions.     

7-Aryl-4a-hydroxy-4a,6,7,7a-tetrahydroisoxazolo[4,5-b]quinuclidines as NO Donors

7-Aryl-4a-hydroxy-4a,6,7,7a-tetrahydroisoxazolo[4,5-b]quinuclidines have been prepared from 2-arylmethylene-3-quinuclidones and hydroxylamine and they are able to release NO upon mild oxidation with K₃[Fe(CN₆)] in basic medium.     

Behavior ofZ- andE-s-cis-ferrocenyl-1,3-dienes in cycloaddition and dimerization reactions

Z-3-Ferrocenylmethylene-2-methylenecamphane andE-2-ferrocenylmethylene-3-methylenequinuclidine were synthesized by isomerization of the corresponding isomericE- andZ-1,3-dienes in an acidic medium. The dienes obtained form [4+2]-cycloadditionendo-adducts withN-phenylmaleimide, do not form cyclodimers upon thermal or acid-catalyzed [4+2]-cyclodimerization, and addZ-3-ferrocenylmethylene-1,2,7,7-tetramethylbicyclo[2.2.1]hept-2-ylium andE-2-ferrocenylmethylene-3-methyl-1-azoniabicyclo[2.2.1]oct-3-ylium salts, respectively, at the terminal methylene group to give linear addition products. The latter undergo fragmentation on treatment with HBF₄ to form the corresponding carbocation tetrafluroborates. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1223–1228, June, 1998.