3-exo,3′-exo-(1R,1′R)-Bithiocamphor — a versatile source for functionally different 3,3′-bibornane derivatives, II. 1 An access to 3-exo,3′-exo-(1r,1′r)-bicamphor and related compounds

3-exo,3′-exo-(1R,1′R)-bicamphor (12) is obtained from 3-exo,3′-exo-(1R,1′R)-bithtiocamphor (3) by condensation with hydrazine hydrate followed by hydrolysis of the resulting dihydropyridazine 11. Deprotonation of 12 with NaH and subsequent treatment with potassium hexacyanoferrate (III) furnishes the 2,2′-dioxo-3,3′-bibornanylidene 13, whilst reduction of 12 with L1AlH₄ affords the 3,3′-biisoborneol 16. Further related transformations to various 2,2′-difunctional 3,3′-bibornane derivatives are described, which are could be of interest as chiral ligands     

Oligomeric flavanoids. Part 13. Synthesis of profisetinidins based on (−) robinetinidol and (+) -epifisetinidol

Acid-catalyzed condensation of (+)-mollisacacidin-[(2R, 3S, 4R)-2, 3-trans-3, 4-trans-flavan-3,3′,4,4′,7-pentaol] with an excess of (−)-robinetinidol[(2R,3S)-2,3-trans-flavan-3,3′,4′,5′,7-pentaol] afforded a novel series of bi-, tri-, and tetraflavanoid profisetinidins. They are accompanied by (−)-fisetinidol-(4,2′)-(−)-robinetinidol which results from the pyrogallol B-ring of (−)-robinetinidol serving as nucleophile competing with its resorcinol A-ring in coupling with a C-4 carbocationic intermediate. Similar condensation with (+)-epifisetinidol[(2S,3S)-2,3-cis-flavan-3,3′,4′,7-tetraol] led to the exclusive formation of [4,6]-interflavanyl bonds, these units being ‘linearly’ arranged in the tetraflavanoid analogue in contrast to the ‘branched’ nature of the (−)-robinetinidol homologue.     

Structures of 3,3′-dicarbometoxy-2,2′-bipyridine complexes with silver(I) and copper(II) cations

The structures of 3,3′-dicarbometoxy-2,2′-bipyridine (dcmbpy) complexes with copper(II) and silver(I) cations have been determined using single crystal X-ray-diffraction. The crystals of Cu(dcmbpy)Cl₂ are monoclinic, C2/c, a = 16.966(3), b = 18.373(3), c = 13.154(2) Å, β = 126.543(3)°. The crystals of Ag(dcmbpy)NO₃ · H₂O are also monoclinic, C2/c, a = 16.7547(13), b = 11.0922(9), c = 18.7789(18) Å, β = 100.228(7)°. The results have been compared with the literature data on the complexes of dcmbpy and its precursors: 2,2′-bipyridine (bpy) and 3,3′-dicarboxy-2,2′-bipyridine (dcbpy). Two types of complexes of 3,3′-carboxy derivatives of bpy are distinguished: (1) with metal atom bonded to two N atoms of the same molecule and (2) with metal atom bonded to two N atoms of two different molecules. The Cu(dcmbpy)Cl₂ complex belongs to the first type, whereas Ag(dcmbpy)NO₃ · H₂O belongs to the second type.     

H, C, N NMR, ESI mass spectral and single crystal X-ray structural characterization of three spiro[pyrrolidine-2,3′-oxindoles]

Three spiro[pyrrolidine-2,3′-oxindoles], 1,1′,2,2′,5′,6′,7′,7′a-octahydro-2-oxo-1′-phenyl-spiro[3H-indole-3,3′-[3H]-pyrrolizine]-2′-carboxylic acid methyl ester (1), 1,1′,2,2′,5′,6′,7′,7′a-octahydro-2-oxo-1′-nitro-2′-phenyl-spiro[3H-indole-3, 3′-[3H]-pyrrolizine] (2) and 1,1′,2,2′,5′,6′,7′,7′a-octahydro-2-oxo-1′-nitro-2′-(4″-chlorophenyl)-spiro[3H-indole-3,3′-[3H]-pyrrolizine] (3) have been synthesized and their ¹H, ¹³C and ¹⁵N spectra assigned. The chemical shift assignments are based on Pulsed Field Gradient (PFG) Double Quantum Filter (DQF) ¹H, ¹H correlation spectroscopy (COSY), PFG ¹H, ¹³C Heteronuclear Multiple Quantum Coherence (HMQC) and PFG ¹H,X (X = ¹³C and ¹⁵N) Heteronuclear Multiple Bond Correlation (HMBC) experiments. The single crystal X-ray structures of 1–3 have been determined. Compounds 1 and 2 crystallized in monoclinic space group C2/c and compound 3 in monoclinic space group P2₁/c, respectively. Also the ESI-TOF MS data of 1–3 are given.     

Ab initio study of rotational isomerism and electronic structure of isomeric bipyrroles

Ab initio calculations using STO-3G and 4-31G basis sets have been performed on the internal rotation barriers and conformational stabilities for 2,3′- and 3,3′-bipyrrole. The twofold rotation potential predicted for both isomers at minimal basis level becomes a more involved fourfold potential when the split-valence basis set is employed, because it takes into account more properly the nonbonded interannular interactions. A transoid-gauche minimum is predicted to have the minimal absolute conformational energy in both isomers. The electronic structure of the highest occupied MOs of 2,2′-, 2,3′- and 3,3′-bipyrrole are analyzed in terms of the single pyrrole MO pattern and a similar difficulty in removing electrons from the HOMOs in going from one isomer to another is predicted, even if a deviation from planarity occurs.     

New 6,6'-disubstituted-binaphthol derivatives as chiral dopants: Synthesis and temperature dependence of molecular conformations

A number of new chiral binaphthol (BN) derivatives with different substituents R,R' in the 6,6'-positions in open (BN-diethylethers) and bridged forms (BN-acetals) have been synthesized. The syntheses of the chiral 6,6'-disubstituted-2,2'-diethoxy-1,1'-binaphthyls (R,R' = -CH'CHCHO, -CH'CH-(p-BrPh), -CH'CH-(p-CHOPh)) and the chiral 9,14-disubstituted-dinaphtho [2,1-d:1',2'-f][1,3] dioxepins with R,R' = -CH'CH-(p-BrPh), -CH'CH-(p-CHOPh) are reported for the first time. The possible liquid crystalline properties and molar twisting powers (β_M) in three different nematic liquid crystals (LCs) of the BN derivatives were investigated. Derivatives with spatially extended substituents in the 6,6'-positions (e.g. styryl or vinyl) show unusually high molar twisting power (up to 124.5μm^-1). A direct correlation between the magnitude of β_M and the length of the substituents was found. Bridged forms, in which the dihedral angle θ between the naphthyl moieties is ≊ 54°, show higher twisting power than the corresponding open forms, where θ is allowed to vary around 90° resulting in an equilibrium between transoid and cisoid forms. From the different temperature dependencies of β_M of the open and bridged BN_s, a molecular model was developed relating the molecular conformation and twisting power. Although no mesophase was found in any of the compounds synthesized, they can be considered as important precursors for the synthesis of potential chiral BN-containing LCs.     

Conformational and structural analysis of N-N′-bis(4-methoxybenzylidene)ethylenediamine

The Schiff base compound, N-N′-bis(4-methoxybenzylidene)ethylenediamine (C₁₈H₂₀N₂O₂) has been synthesized and its crystal structure has been investigated by X-ray analysis and PM3 method. The compound crystallizes in monoclinic space group P2₁/n with a=10.190(1), b=7.954(1), c=10.636(1) Å, β=111.68(1)°, V=801.1(1) ų, Z=2 and D_cal=1.229 Mgm⁻³. The title structure was solved by direct methods and refined to R=0.056 for 2414 reflections [I>3.0σ(I)] by full-matrix anisotropic least-squares methods. The energy profile of the compound was calculated by PM3 method as a function of θ[N1′–C9′–C9–N1]. The most stable molecular structure of the title compound is the anti conformation, which is different in energy by 5.0 and 1.0 kcal mol⁻¹ from the eclipsed conformation I and gauche conformations, (III and V), respectively.     

X-ray crystal structure analysis and atomic charges of color former and developer: 2. Color formers

The crystal and molecular structures of 2′-amino-6′-dibutylamino-3′-methylspiro[isobenzofuran-1(3H), 9′[9H]xanthen]-3-one (1), 2′-amino-6′-(N-cyclohexyl-N-methylamino)-3′-methylspiro[isobenzofuran-1(3H), 9′[9H]xanthen]-3-one (2) and 2′-(2-chlorophenyl)amino-6′-dibutylaminospiro[isobenzofuran-1(3H), 9′[9H]xanthen-3-one (3) have been determined by single-crystal X-ray diffraction analysis. Atom-atom non-bonded potential energy and semiempirical quantum chemical calculations have been performed. The xanthene rings of 1 to 3 are slightly bent and the phthalide rings are planar. The phthalide ring moieties are almost perpendicular (88.9(1)−93.5(5)°) to the xanthene rings. The bond lengths C(6)---O(2) are apparently extended from the normal C(sp³)---O (lactone) length. The temperature factors for one butyl group C(32)---C(35)) of 1 increase gradually toward the terminal carbon. The temperature factors for C(30)---C(33) of 2 indicate large vibrations and these are reflected in short bond lengths. Two butyl groups of 3 are disordered and these C---C bond lengths are short and long alternately. Atomic net charges around spirocarbon C(6) and toward N(1) to C(6) indicate the weak alternative system in the colorless form. As the xanthene ring has a planar geometry, the π electron density migration will easily occur from the auxochromes attached to the phthalide ring to the xanthene ring.     

X-ray crystal structure analysis and atomic charges of color former and developer: 2. Color formers

The crystal and molecular structures of 2′-amino-6′-dibutylamino-3′-methylspiro[isobenzofuran-1(3H), 9′[9H]xanthen]-3-one (1), 2′-amino-6′-(N-cyclohexyl-N-methylamino)-3′-methylspiro[isobenzofuran-1(3H), 9′[9H]xanthen]-3-one (2) and 2′-(2-chlorophenyl)amino-6′-dibutylaminospiro[isobenzofuran-1(3H), 9′[9H]xanthen-3-one (3) have been determined by single-crystal X-ray diffraction analysis. Atom-atom non-bonded potential energy and semiempirical quantum chemical calculations have been performed. The xanthene rings of 1 to 3 are slightly bent and the phthalide rings are planar. The phthalide ring moieties are almost perpendicular (88.9(1)–93.5(5)°) to the xanthene rings. The bond lengths C(6)---O(2) are apparently extended from the normal C(sp³---O (lactone) length. The temperature factors for one butyl group C(32)---C(35)) of 1 increase gradually toward the terminal carbon. The temperature factors for C(30)---C(33) of 2 indicate large vibrations and these are reflected in short bond lengths. Two butyl groups of 3 are disordered and these C---C bond lengths are short and long alternately. Atomic net charges around spirocarbon C(6) and toward N(1) to C(6) indicate the weak alternative system in the colorless form. As the xanthene ring has a planar geometry, the π electron density migration will easily occur from the auxochromes attached to the phthalide ring to the xanthene ring.     

The crystal and molecular structure of N′-monomethylthiobinupharidine iodide dihydrate - the methiodide of nuphar alkaloid

The crystal structure of N′-monomethylthiobinupharidine iodide dihydrate has bee determined by single-crystal X-ray analysis. The crystals are orthorhombic, space group P2₁2₁2₁, with = 9.499(3), b = 15.522(5), c = 23.694(7) A. Block-diagonal least-squares refinement, with 2060 reflections measured on diffractometer, yielded a final value for R of 0.073. The cation was found to have a skeleton composed of two trans-quinolizidine systems with equatorially bonded methyl and furan groups; the central part of the cation (the tetrahydrothiophene ring) adopts a conformation between envelope and half-chair. Quaternization at the N(5′) atom does not change conformation of the quinolizidine. The results of X-ray analysis confirm the interpretation of the ¹³C NMR spectra.     

Chains, ladders and sheets of d metal–organic polymers generated from the flexible bipyridyl ligands

By use of the three-layer diffusion method, reactions of flexible bipyridyl ligands (4,4′-bpp or 3,3′-bpp) with M(II) salts (M = Zn, Cd) and multi-carboxylate ligands resulted in the formation of four interesting d¹⁰ metal–organic coordination polymers: [Zn(μ-4,4′-bpp)Br₂]_n (1), [Zn(μ-4,4′-bpp)(1,2-bdc)]_n · nH₂O (2), [Zn(μ-3,3′-bpp)(1,3-bdc)]_n · nCH₃OH · 2nH₂O (3) and [Cd(μ-3,3′-bpp)(C₄H₂O₄)]_n · 3nH₂O (4) (4,4′-bpp = 2,2′-bis(4-pyridylmethyleneoxy)-1,1′-biphenylene; 3,3′-bpp = 2,2 ′-bis(3-pyridylmethyleneoxy)-1,1′-biphenylene; bdc=benzenedicarboxylate, C₄H₄O₄ = fumaric acid). Complex 1 has a 2D sheet structure consisting of two unusual zigzag Zn(II) chains which are nearly perpendicular to each other. Complex 2 is comprised of two-leg ladders, in which [Zn(4,4′-bpp)] chains serve as the side rails and 1,2-bdc ligands serve as the cross rungs. In complex 3, every two 1,3-bdc ligands connect the neighbouring Zn(II)-3,3′-bpp dimetallic rings in η¹ coordination modes into an interesting chain structure. Complex 4 consists of an anionic macrocycle-containing cadmium dicarboxylate sheets that are separated by 3,3′-bpp. These d¹⁰ metal complexes exhibit high thermal stabilities and strong luminescence efficiencies.     

Model compounds of nylons—II : The crystal structure of N,N′-bis (β-chlorethyl)-glutaramide

The crystal structure of N,N′-bis(β-chloroethyl)-glutaramide (NNCEG) has been determined by X-ray diffraction analysis, as part of a research programme on simple model compounds for synthetic polyamides. It crystallizes in the monoclinic system, space group P2₁ Z = 2, with A = 4·941, B = 28·123, C = 4·835 Å and β = 113°53′. The structure was solved by the heavy atom method and refined to a final R value of 0·079. Each molecule forms hydrogen bonds along two directions (almost the a and the c directions with an angle close to 60°) giving rise to bidimensional layers (parallel to the ac plane with width b/2). A similar system of hydrogen bonds could be postulated for some nylons with odd number of CH₂'s between amide groups. The molecular conformation different from an all trans conformation is discussed in terms of the barriers to rotation around each bond considered by several authors. The twinning observed in most of the examined crystals is rationalized in terms of simple symmetry operations on molecular conformations of opposite chirality.     

Synthesis, water stability and proton conductivity of novel sulfonated polyimides from 4,4′-bis(4-aminophenoxy)biphenyl-3,3′-disulfonic acid

A novel sulfonated diamine monomer, 4,4′-bis(4-aminophenoxy)biphenyl-3,3′-disulfonic acid (BAPBDS) with the high basisity and flexible structure was synthesized by direct sulfonation of 4,4′-bis(4-aminophenoxy)biphenyl (BAPB). Sulfonated polyimides (SPIs) were prepared from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), BAPBDS and nonsulfonated diamines such as BAPB. The SPI membranes showed much higher water stability at high temperatures than other sulfonated diamine-based SPIs reported so far. Their water vapor sorption isotherm, water uptake (WU), density, dimensional change and proton conductivity σ were investigated. The SPIs showed rather isotropic dimensional changes with WU and the volume increases were slightly smaller than those estimated from the additivity. The SPIs with ion exchange capacities (IECs) of 1.9–2.7 meq/g displayed the similar relationship between σ and WU each other, which was different from those of Nafion 117 and also of the SPIs with the lower IECs. The former SPIs showed reasonably high σ values of 10⁻² S/cm or more even at WU of 25 g/100 g dry polymer under 70% RH at 50 °C, whereas the latter showed the similarly high σ values only in liquid water, but not in the nearly saturated water vapor.     

Intramolecular meta photocycloaddition of 6-arylhex-2-enes Part 2

The course of the intramolecular meta photocycloaddition of ring-substituted (E)- and (Z)- 6-phenylhex-2-enes depends on the position and nature of the substituent. In this paper, the effects of methyl and cyano groups and the fluorine atom are described. The results are in agreement with a reaction mechanism in which the excited phenyl ring becomes polarized when it is approached by the alkene. The dipolar character becomes particularly apparent in the case of fluorine which, depending on its position, can stabilize either the negative charge through its inductive effect or the positive charge through its mesomeric effect. The configuration of the terminal methyl group sterically influences the photoreaction. The Z alkenes readily undergo the 1′,3′-addition, but fail to add in the 2′,6′-mode, even if substituents which strongly promote this mode are present. The E alkenes seem to suffer from steric hindrance in the 2′,6′- and the 1′,3′-mode, but the electronic effects of activating substituents provide compensation and substituents may have a pronounced influence on the ratio of the two modes.     

Synthesis of 1,1′-methylenedi[(1R,1′R,3R,3′R,5R,5′R)-8-oxabicyclo[3.2.1]oct-6-en-3-ol] and derivatives: precursors of long-chain polyketides

Racemic 1,1′-methylene[(1RS,1′RS,3RS,3′RS,5RS,5′RS)-8-oxabicyclo[3.2.1]oct-6-en-3-ol] ((±)-6) derived from 2,2′-methylenedifuran has been resolved kinetically with Candida cyclindracea lipase-catalysed transesterification giving 1,1′-methylenedi[(1R,1′R,3R,3′R,5R,5′R)-8-oxabicyclo[3.2.1]oct-6-en-3-ol] (−)-6 (30% yield, 98% ee) and 1,1′-methylenedi[(1S,1′S,3S,3′S,5S,5′S)-8-oxabicyclo[3.2.1]oct-6-en-3-yl] diacetate (+)-8, (40% yield, 98% ee). These compounds have been converted into 1,1′-methylenedi[(4S,4′S,6S,6′S)- and (4R,4′R,6R,6′R)-cyclohept-1-en-4,6-diyl] derivatives.     

Studies on the synthesis of biphenylneolignans. Part 1: Enantioselective synthesis of (S,S)- and (R,R)-2,2′-dimethoxy-4-(3-hydroxy-1-propenyl)-4′-(1,2,3-trihydroxypropyl)diphenyl ether

Two erythro-isomers of 2,2′-dimethoxy-4-(3-hydroxy-1-propenyl)-4′-(1,2,3-trihydroxypropyl)diphenyl ether, (7′S, 8′S)-9 and (7′R, 8′R)-9, were synthesized in seven steps, in which an improved method for the synthesis of the key intermediate 3 was developed. The absolute configuration of the target molecules was also confirmed.     

Polyhydroxylated pyrrolizidines. Part 3: A new and short enantiospecific synthesis of (+)-hyacinthacine A2

(1R,2R,3R,7aR)-1,2-Dihydroxy-3-hydroxymethylpyrrolizidine (+)-Hyacinthacine A₂ 1 has been synthesized by Wittig's methodology using [(2′S,3′R,4′R,5′R)-3′,4′-dibenzyloxy-N-tert-butyloxycarbonyl-5′-tert-butyldiphenylsilyloxymethylpyrrolidin-2′-yl]carbaldehyde 3, prepared from a partially protected DMDP 2, and the appropriated ylide, followed by cyclization by an internal reductive amination process of the resulting unsaturated aldehyde 4 and total deprotection.     

Anomalous electric birefringence behavior of sonicated DNA fragments as observed in reversing-pulse transients and steady-state sign reversal: a multicomponent approach

Anomalous electric birefringence signals of a sonicated and column-fractionated medium-size calf thymus DNA sample (bp  =  570) in Na⁺ solutions were measured at 7 °C. The reversing-pulse electric birefringence (RPEB) signal pattern was theoretically calculated in the low electric field region for two axially symmetric models coexisting in equilibrium in solution. The RPEB theory is based on the electric dipole moment due to ion-fluctuation along the longitudinal direction and the electric polarizability anisotropy (Δ′), together with various electric and optical parameters assigned to the models. An analytical method was developed for the steady-state birefringence of the two-component system in a wide range of electric fields. The NaDNA samples exhibit complex RPEB patterns mixed with negative- and positive-going profiles. An experimental RPEB signal of NaDNA at an absorbance (A₂₆₀) of 8 was fitted to theoretical curve at weak electric fields. The anomalous RPEB signal was attributed to the component 2, which shows a dip in the buildup and another in the reverse processes with a positive sign and a larger relaxation time. For the component 1, a normal DNA profile with negative sign is associated with a narrow dip in the reverse and a faster relaxation time in the decay signal. The field-strength dependence of observed steady-state birefringence δ(∞) could be fitted for NaDNA at A₂₆₀  =  8 by the SUSID orientation function with saturated ionic and electronic moments. An apparent positive maximum and the sign reversal in δ(∞) at weak electric fields is an interplay between the positive component 2 with positive optical factor Δg and negative Δ′ and the negative component 1 with negative Δg and positive Δ′. Possible conformation of two DNA components involved in solution was estimated.     

Homoleptic carbene complexes VI. Bis{1,1′-methylene-3,3′-dialkyl-diimidazolin-2,2′-diylidene}palladium chelate complexes by the free carbene route

1,1′-Methylene-3,3′-dialkyldiimidazolium salts have been deprotonated with n-butylithium in the presence of palladium(II) iodide to give the percarbene complexes 1 (alkyl=Me) and 2 (alkyl=Et), each containing two bidentate 1,1′-methylene-3,3′-dialkyldiimidazolin-2,2′-diylidene chelate ligands. The X-ray structure analysis of 1 reveals a stereochemistry in which the two spiro-linked six-membered metallacycles adopt boat-like conformations strongly bending out of the PdC₄ coordination plane in opposite directions. The carbenoid imidazole rings, which are rotated by +42 and −43°, respectively, relative to this plane, break down into two tightly bound π-systems (N=4C=4N,= C=C) connected by long C---N bonds.     

Synthesis of (+)-carpamic acid from (+)-alanine

(+)-Carpamic acid [(2′R,5′S,6′S)-8-(5′-hydroxy-6′-methylpiperidin-2′-yl)octanoic acid, 1] was synthesized from (S)-alanine, employing intramolecular and reductive amination of acyclic amino ketone 8 as the key step to generate the piperidine ring.