E.S.R. and D.S.C. investigations of phase transitions in polymorphic 4-n-alkoxybenzylidene-4′-n-alkylanilines

Abstract

It is shown that the McMillan parameter M = T _SAN/T _N1 (where T _SAN and T _NI are respectively the temperatures of the smectic A to nematic (SAN) and the nematic to isotropic (NI) phase transitions) is useful in analysing the crossover between second and first order behaviour of the S_NN transition in the nO.m homologous liquid crystal series (the 4-n-alkoxybenzylidene-4′-n-alkylanilines). Using a phase diagram of orientational ordering versus M for this series, as obtained in this work (from E.S.R. and D.S.C), a symmetric tricritical point with mean field exponent β₂ = 1 is demonstrated. In a preliminary study of E.S.R. linewidth parameters B and C of nitroxide spin probes dissolved in members of the nO.m series exhibiting a first order S_AN transition, critical-type divergences are observed near this transition. In the case where M is closer to 0.959 (the value at the tricritical point), these divergences appear similar to those previously observed in related nO.m members with a second order S_AN transition; however, they are considerably enhanced for an M value closer to unity (i.e. more removed from the tricritical point). This indicates the importance of coupling between orientational and positional order parameters in the observed critical-type divergences.     

Chemistry of condensed thiophenes. V. Sulfonation and sulfonyl bridging of m-terphenyl. Conversion to sulfonamides

Reaction of m-terphenyl with 20% oleum at 100° gives both disulfonation and double sulfonyl bridging to yield benzo[1]thieno[2,3-b]dibenzothiophene-3,9-disulfonic acid 5,5,7,7-tetraoxide, isolated as the disodium salt (24%) and convertible (via the disulfonyl chloride) to the bis-sulfonanilide (44%) and the bis-N-butylsulfonamide (40%). Analogously, reaction of m-terphenyl with chlorosulfonic acid at 100° gives disulfonation plus only single sulfonyl bridging to produce 2-(4-chlorosulfonyl)-7-chlorosulfonyldibenzothiophene 5,5-dioxide (80%), convertible to the corresponding bis-sulfonanilide (63%) and the bis-N-butylsulfonamide (45%).     

Oxazolochlorins. 14.

The structure of 8‐oxo‐5,10,15,20‐tetraphenyl‐7‐oxaporphyrin N²⁴‐oxide, C₄₃H₂₈N₄O₃, (4B), shows that N‐oxidation of the pyrrole opposite the oxazolidone group cants the pyrrole out of the mean plane of the chromophore. This also affects the oxazolidone group, which is also slightly canted out. This conformation is qualitatively similar to that of the parent meso‐tetraphenylporphyrin N‐oxide, but dissimilar to that of the porpholactone N‐oxide isomer 8‐oxo‐5,10,15,20‐tetraphenyl‐7‐oxaporphyrin N²²‐oxide, (4A), carrying the N‐oxide at the oxazolidone group. While the degree of canting of the N‐oxidized groups in both cases is comparable (and more pronounced than in the porphyrin N‐oxide case), in (4A) the pyrrolic groups adjacent to the N‐oxidized group are more affected than the opposing group. These differences in the conformational modes may contribute to rationalizing the distinctly different electronic properties of (4A) and (4B).     

Irreversible enzyme inhibitors. LXXXIII. Candidate active-site-directed irreversible inhibitors of dihydrofolic reductase. VIII. Derivatives of 2,4-diaminopyrimidine. II

2,4-Diamino-6-(p-aminophenethyl)pyrimidines with a 5-phenylbutyl (XIX) and 5-(p-chlorophenyl) (VIII) substituent were synthesized by condensation of the corresponding pyrimidine-6-carboxaldehydes (XVI, X) with the Wittig reagent derived from p-nitro-benzyl bromide, followed by catalytic hydrogenation. Selective bromoacetylation of VIII and XIX afforded the candidate active-site-directed irreversible inhibitors of dihydrofolic reductase, namely, 6-(p-bromoacetamidophenethyl)-2,4-diaminopyrimidine with a 5-(p-chlorophenyl)- (IV) and 5-phenylbutyl- (III) substituents. Although III and IV were excellent reversible inhibitors of dihydrofolic reductase, neither showed any inactivation of the enzyme; in contrast, the corresponding 2-amino-6-(p-bromoacetamidophenethyl)-5-phenylbutyl-4-pyrimidinol (II) - which differs from III only in the 4-substituent (NH₂ vs. OH) - was an excellent active-site-directed irreversible inhibitor of dihydrofolic reductase, but II was a poor reversible inhibitor. Thus the conformations of II and III are most probably different when complexed to dihydrofolic reductase.     

Electron-transfer polymers. XXIX. Copolymerizability of vinylhydroquinone derivatives

Ten vinylhydroquinone and one vinyl resorcinol derivatives are compared, particularly with respect to NMR spectra and copolymerizability with styrene. They are vinylhydroquinone dimethyl ether (I), vinyl-O,O′-bis(1-ethoxyethyl)hydroquinone (II), vinylhydroquinone di(2-pentyl)ether (III), 4-vinyl resorcinol bismethoxymethyl ether (IV), 2-vinyl-5-methylhydroquinone dimethyl ether (V), 2-vinyl-5-methyl-O,O′-bis(1-ethoxyethyl)hydroquinone (VI), 2-vinyl-6-methylhydroquinone dimethyl ether (VII), 2-vinyl-5-tert-butylhydroquinone dimethyl ether (VIII), 2-vinyl-5-chlorohydroquinone dimethyl ether (IX), 2-vinyl-3,6-dimethylhydroquinone dimethyl ether (X), and 2-vinyl-3,5,6-trimethylhydroquinone dimethyl ether (XI). All the vinyl protons have almost the same coupling constants. Though subtle distinctions are found among all the spectra, they can in general be put into two groups on the basis of the chemical shifts. Let the hydrogen on carbon-1 of the vinyl group be A, the hydrogen cis to A be B the hydrogen trans to A be C, then in the first group, (I) through (IX), the chemical shifts (τ) are (A) 3.02 ± 0.08, (C) 4.41 ± 0.05, and (B) 4.87 ± 0.07, and in the second group, (X) and (XI), they are (A) 3.30 ± 0.03, (C) 4.49 ± 0.01, and (B) 4.59 ± 0.03. It is supposed that in (X) and (XI) the vinyl group is out of the plane of the ring, because of the two ortho substituents, and this conformation is reflected in the NMR data. Ultraviolet spectra are consonant with this interpretation, since the λ_max of (X) and (XI) correspond closely with those of nonvinyl reference compounds, while those of (II), (V), and (VIII) are shifted to longer wavelengths. When these compounds are copolymerized separately with styrene, the behaviors are classifiable into the following three groups, where r₁ and r₂ are monomer reactivity ratios with styrene as the first monomer: (i) r₁ < 1 and r₂ < 1 for compounds (II) and (III) and the reference compound O,O′-dibenzoylvinylhydroquinone, (ii) r₁ < 1 and r₂ > 1 for compounds (I), (V), (VII), (VIII), (IX), and (iii) r₁ > 1 and r₂ = 0 for compounds (X) and (XI). These behaviors are correlated with the effect of electronegativity of groups on the stability of the radical at the growing end of the chain and with the simultaneous effects of steric hindrance.     

Cation radicals. XXXII. Reaction of N-ethylcarbazole with iodine-silver salts. Nitration of N-ethylcarbazole

Reaction of N-ethylcarbazole ( 1 ) with iodine-silver perchlorate gave a green solution having a singlet esr signal. Reduction of the solution with potassium iodide gave N,N′ -diethyl-3,3′-dicarbazolyl ( 3 , 48%). Small amounts of 3-iodo- ( 4 ) and 3,6-diiodo-N-ethylcarbazole ( 5 ) were also obtained. Compounds 4 and 5 are believed to have been formed by electrophilic iodination of 1 by I₂-AgCIO₄, whereas 3 appears to have been formed via the dimerization of 1 ^.+. In accord with this, reaction of 1 with iodine-silver nitrite gave 3-nitro-N-ethylcarbazole ( 6 , 61%), 9% of another nitro-N-ethylcarbazole ( 7 ), thought to be either 1- or 4-nitro-N-ethylcarbazole, and 28% of 4. Thus, trapping of 1 ^.+ by nucleophilic nitrite ion occurred even though 1 ^.+ is not stable enough toward isolation as the perchlorate.     

Structural characterisation of a water-soluble polysaccharide from tissue-cultured Dendrobium huoshanense C.Z. Tang et S.J. Cheng

A water-soluble polysaccharide TC-DHPA4 with a molecular weight of 8.0 × 10⁵ Da was isolated from tissue-cultured Dendrobium huoshanense by anion exchange and gel permeation chromatography. Monosaccharide analysis revealed that the homogeneous polysaccharide was made up of rhamnose, arabinose, mannose, glucose, galactose and glucuronic acid with a molar ratio of 1.28:1:1.67:4.71:10.43:1.42. The sugar residue sequence analysis based on the GC-MS files and NMR spectra indicated that the backbone of TC-DHPA4 consisted of the repeated units:→6)-β-Galp-(1→6)-β-Galp-(1→4)-β-GlcpA-(1→6)-β-Glcp-(1→6)-β-Glcp-(→. The sugar residue sequences β-Glcp-(1→)-α-Rhap-(1→3)-β-Galp-(1→, β-Glcp-(1→4)-α-Rhap-(1→3)-β-Galp-(1→, β-Galp-(1→6)-β-Manp-(1→3)-β-Galp-(1→, and α-l-Araf-(1→2)-β-Manp-(1→3)-β-Galp-(1→ were identified as the branches attached to the C-3 position of (1→6)-linked galactose in the backbone.     

13C n.m.r. spectra of some polychloroalkenes

¹³C n.m.r. spectra have been measured for thirty-two polychloroalkenes including (i) monosubstituted compounds CH₂?CHCCl_nH_2?nX, where ? X stands for ? H, ? Cl, alkyl, and trisubstituted alkenes CCl₂?CHAlk, none of which form geometric isomers; (ii) disubstituted compounds RCH?CHR′; (iii) and (iv) trisubstituted compounds of the types RCCl?CHR′ and CHCl?CClR, respectively. Compounds (ii) to (iv) represent either individual isomers or mixtures of the Z and E forms. In the case of compounds (ii) and (iii), the ordering of chemical shifts is δ_E > δ_Z for the sp²-carbon atoms and δ_E < δ_z for the adjacent tetrahedral ones. On the contrary, the signals of the sp²-carbon atoms of compounds (iv) obey the rule δ_E < δ_z. The effect of vinyl and allyl groups as substituents on the ¹³C chemical shifts of chlorine-containing groups is discussed. The dependence of the sp²-carbon spin–spin coupling constants J(¹³C? ¹H) on the number of chlorinated substituents in the molecule is also considered.     

Chemistry of thienopyridines. XXXVIII. Diels-Alder reactions of thienopyridine sulfones. Part 2

Thieno[3,2-b]pyridine 1,1-dioxide ( 2 ) undergoes Diels-Alder condensation with the dienophiles cyclopentadiene, anthracene, and naphthacene in a manner analogous to its isomer thieno[2,3-b]pyridine 1,1-dioxide ( 1 ). Compound 2 dimerizes in refluxing xylene with the loss of sulfur dioxide plus either the loss or transfer of hydrogen to give a small yield (ca. 2%) of pyrido[2′,3′:4,5]thieno[3,2-f]quinoline 7,7-dioxide ( 7 ) and its 5,6-dihydro derivative 12 . Formation of 7 and 12 are compared and contrasted with products reported from dimerization of 1 and of benzo[b]thiophene 1,1-dioxide and its derivatives.     

Indolalkaloids of Pleiocarpa talbotii Wernham. 145. Alkaloids

Besides talbotine ( 1 ) three new indole alkaloids, talpinine ( 2 ), talcarpine ( 3 ) and 16-epi-affinine ( 4 ) were isolated from the stem bark of Pleiocarpa talbotii Wernham. The structure of 2 was deduced by chemical degradation and by analyses of the spectra of the alkaloid and its derivatives. One of these derivatives is identical with talcarpine ( 3 ). The structures 2 and 3 are similar to that of macroline ( 14 ), a splitting product of the bisindole alkaloid villalstonine from Alstonia species. 16-epi-Affinine ( 4 ) was chemically correlated with the known alkaloid vobasine ( 19 ). Talpinine ( 2 ) and 16-epi-affinine ( 4 ) were also isolated from the root bark of Pleiocarpa talbotii.     

Head-to-head vinyl polymers. X. Cyclopolymerization of o-dimethacryloyloxybenzene

To clarify the possibility of preparing a polymer that contained head-to-head (h–h) methyl methacrylate (MMA) unit radical cyclopolymerization of o-dimethacryloyloxybenzene (o-DMB) was investigated. p-Dimethacryloyloxybenzene (p-DMB) was also used in comparison. When the polymerizations were carried out with higher monomer concentrations than ca. 0.5 mol/L, benzene-insoluble polymer was produced. The extent of cyclization (f_c) in benzene-soluble polymer increased with a decrease in the monomer concentration and an increase in the polymerization temperature. The ¹H-NMR and ¹³C-NMR spectra of poly(MMA) derived from poly(o-DMB) by hydrolysis and methylation were in fairly good agreement with those of ordinary head-to-tail (h–t) poly(MMA). Therefore, it was concluded that the intramolecular propagation in cyclopolymerization of o-DMB was mainly performed by a h–t mechanism. However, the initial and maximum degradation temperatures of the poly(MMA) were observed to be somewhat higher than those of the ordinary poly(MMA), which suggests that a minor amount of the h–h unit was formed.     

Glycosylidene Carbenes. Part 2. Synthesis of O-Aryl Glycosides

Phenol, 4-methoxyphenol, 4-nitrophenol, methyl orsellinate ( 1 ), and 2,6-di(tert-butyl)-4-methylphenol (BHT; 2 ) have been glycosylated by thermal reaction (20–60°) with various glycosylidene-derived diazirines. 4-Methoxyphenol reacted with the D-glucosylidene-derived diazirine 3 to give O-glucosides ( 4 and 5 , 69%, 3:1) and C-glucosides ( 6 and 7 , 16%, 1:1). Similarly, phenol yielded O-glucosides ( 10 and 11 , 70%, 4:1) and C-glucosides ( 12 and 13 , 13%, 1:1). 4-Nitrophenol gave only O-glycosides, 3 leading to 14 and 15 (75%, 3:2; Scheme 1), and the D-galactosylidene-derived diazirine 17 to 22 and 23 (52% (from 16 ), 65:35; Scheme 2). The reaction of phenol with 17 yielded 58% (from 16 ) of the O-galactosides 18 and 19 (4:1) and 14% of the C-galactosides 20 and 21 (1:1). From the D-mannosylidene-derived diazirine 25 , we predominantly obtained the α-D-configurated 26 (38 % from 24 ). These results are interpreted by assuming that an intermediate (presumably a glycosylidene carbene) first deprotonates the phenol to generate an ion pair which combines to give O- and - with electron-rich phenolates - also C-glycosides. A competition experiment of 3 with 4-nitro- and 4-methoxyphenol gave the products from the former ( 14 and 15 ) and the latter phenol ( 4-7 ) in almost equal amounts. Differences in the kinetic acidity of OH groups, however, may form the basis of a regioselective glycosidation, as evidenced by the reaction of 3 with methyl orsellinate ( 1 ) yielding exclusively the 4-O-monoglycosylated products 27 and 28 (78%, 85:15), although diglycosidation is possible ( 27 → 31 and 32 ; 67%, 4:3; Scheme 3). Steric hindrance does not affect this type of glycosidation; 3 reacted with the hindered BHT ( 2 ) to afford 33 and 34 (81 %, 4:1). The predominant formation of 1,2-trans -configurated O-aryl glycosides is rationalized by a neighbouring-group participation of the 2-benzyloxy group.     

Anionic polymerization of N-substituted maleimide. II. Polymerization of N-ethylmaleimide

Anionic polymerization of N-ethylmaleimide (N-EMI) was carried out with potassium t-butoxide, lithium t-butoxide, n-butyllithium, and ethylmagnesium bromide as initiators in THF and in toluene. An almost quantitative yield of poly(N-EMI) was obtained with potassium t-butoxide as initiator in THF in a wide range of polymerization temperatures. Initiators possessing lithium as counter cation produced poly(N-EMI) in slightly lower yields and ethylmagnesium bromide gave the polymer only in less than 35% yield in THF. As a polymerization reaction solvent, THF was preferable for the polymerization of N-EMI compared with toluene with respect to polymer yields. Poly(N-EMI) obtained with anionic initiators exerted unimodal molecular weight distribution. From ¹H- and ¹³C-NMR spectra of poly(N-EMI) anionic polymerization of N-EMI with potassium t-butoxide was revealed to proceed at carbon–carbon double bond. t-Butoxide system was found to have a “living” polymerization character, i.e., the observed average degree of polymerization was in good agreement with the one calculated from the initial molar ratio of N-EMI/initiator and the yield of polymer.     

Metabolic Products of Microorganisms. Part 269. 5-Phenylpentadienoic-acid derivatives from Streptomyces sp.

Two new phenylpentadienamides isolated from the culture filtrate of Streptomyces sp. were assigned the structures 5-(4-aminophenyl)penta-2,4-dienamide ( 2 ) and N²-[5-(4-aminophenyl)penta-2,4-dienoyl]-L -glutamine ( 3 ). In addition, 5-(4-aminophenyl)penta-2,4-dienoic acid ( 1 ) has been isolated, and its spectroscopic characteristics are reported for the first time. Compounds 1–3 exist in both the (2E,4E)- and (2E,4Z)-configurations. Electrospray and tandem MS, and HPLC/MS proved to be particularly suitable for the characterization of these metabolites.     

P.M.R. analysis of several phosphorylated aziridines

Several new phosphorylated aziridines of related structure were prepared. P.m.r. analysis via decoupling experiments provided cis H-H, trans H-H, gem H-H and PNCH coupling values. Similar to simple aziridines, the cis H-H coupling is larger than trans H-H coupling (on vicinal ring carbons) which in turn is larger than gem H-H coupling. In one example operating at 100 MHz and 0° it was possible to detect the presence of two invertomers.     

Planarity of benzoyldithiocarbazate tuberculostatics. II. Diesters of benzoyldithiocarbazic acid

The emergence of drug‐resistant strains of Mycobacterium tuberculosis has intensified efforts to identify new lead tuberculostatics. Our earlier studies concluded that the planarity of a molecule correlates well with its tuberculostatic activity. According to our hypothesis, only derivatives whose molecules are capable of adopting a planar conformation may show tuberculostatic activity. The structures of three new potentially tuberculostatic compounds, namely N′‐[bis(methylsulfanyl)methylidene]‐N‐methyl‐4‐nitrobenzohydrazide (denoted G1), C₁₁H₁₃N₃O₃S₂, N′‐[bis(benzylsulfanyl)methylidene]‐N‐methyl‐4‐nitrobenzohydrazide (denoted G2), C₂₃H₂₁N₃O₃S₂, and N′‐[(benzylsulfanyl)(methylsulfanyl)methylidene]‐4‐nitrobenzohydrazide (denoted G3), C₁₆H₁₅N₃O₃S₂, were determined by X‐ray diffraction. The significant distortion from planarity caused by the methyl substituent at the N atom of the hydrazide group or the NO₂ substituent in the aromatic ring leads to the loss of tuberculostatic activity for G1, G2 and G4 {systematic name: N′‐[bis(methylsulfanyl)methylidene]‐2‐nitrobenzohydrazide}. A similar effect is observed when there are large substituents at the S atoms (G2 and G3).     

Irreversible enzyme inhibitors. CXI. Candidate active-site-directed irreversible inhibitors of dihydrofolic reductase derived from 4,6-diamino-1,2-dihydro-l-phenyl-s-triazines. V.

Condensation of 5-(p-nitrophenyl)-2-pentanone with phenylbiguanide hydrochloride (V) gave a 2-methyl-2-(p-nitrophenylpropyl)-1,2-dihydro-s-triazine (IX); hydrogenation of the nitro group to amino followed by bromoacetylation afforded the candidate irreversible inhibitor of dihydrofolic reductase, namely, 2-(p-bromoacetamidophenylpropyl)-4,6-diamino-1,2-dihydro-2-methyl-s-triazine hydrochloride (VIII). Similarly, the o, m, and p-isomers of 5-nitrophenoxy-2-pentanone were converted to the corresponding 2-(bromoacetamidophenoxypropyl)-1,2-dihydro-s-triazines (XI). The four candidate irreversible inhibitors were evaluated on the dihydrofolic reductases from pigeon liver, Walker-256 rat tumor, and L-1210/FR8 mouse leukemia. Only VIII was an irreversible inhibitor; VIII slowly inactivated the L-121-/FR8 mouse leukemia enzyme with a half-life of 2–3 hours at 37°, but VIII showed no inactivation of the other two dihydrofolic reductases—a species specific inactivation.     

Investigation of the composition and stability of the essential oils of origanum vulgare ssp.vulgare L. andO. vulgare ssp.hirtum (Link) letswaart

Summary The essential oils ofOriganum vulgare L. ssp.hirtum (Link) letswaart andOriganum vulgare L ssp.vulgare (Fam. Lamiaceae), cultivated in Hungary, have been studied by GC and GC-MS and the qualitative and quantitative chemical composition of the essential oils in the two species have been compared.O. vulgare ssp.hirtum oil was found to contain carvacrol (76.4%), γ-terpinene (6.6%), thymol (0.23%), andp-cymene (4.7%) as the main constituents whereas the major compounds inO. vulgare ssp.vulgare oil werep-cymene (22.3%), caryophyllene oxide (10.2%), sabinene (7.9%), γ-terpinene (5.1%), thymol (0.34%), and spathulenol (4.8%). The stability of content and composition of the oils during the flowering period (economically beneficial period) were observed. The effect of long-term storage on the composition of the oil was also investigated for both the crude and distilled oil ofOriganum vulgare ssp.vulgare. Presented at Balaton Symposium '01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001     

The non-isothermal thermogravimetric tests of animal bones combustion. Part. I. Kinetic analysis

The non-isothermal combustion of animal bones was investigated by simultaneous thermogravimetric and differential thermal analysis (TG–DTA), in the temperature range ΔT = 20–650 °C. The full kinetic triplet (A, E_a and f(α)) for the investigated process was established, using different calculation procedures: isoconversional (model-free) and the Kissinger's methods. The non-isothermal process occured through three reaction stages (I, II and III). Stage I was described by a reaction model, which contains two competing reactions with different values of the apparent activation energy. The autocatalytic two-parameter Šesták–Berggren (SB) model (conversion function f(α) = α^0.62(1 − α)^3.22), best described the second (II) reaction stage of bone samples. This stage, which corresponds to the degradation process of organic components (mainly collagen), exhibited the autocatalytic branching effect, with increasing complexity. Stage III, attributed to the combustion process of organic components, was best described by an n-th reaction order model with parameter n = 1.5 (f(α) = (1 − α)^1.5). The appearance of compensation effect clearly showed the existence of three characteristic branches attributed to the dehydration, degradation and combustion processes, respectively, without noticable changes in mineral phase. The isothermal predictions of bone combustion process, at four different temperatures (T_iso = 200, 300, 400 and 450 °C) were established in this paper. It was concluded that the shapes of the isothermal conversion curves at lower temperatures (200–300 °C) were similar, whereas became more complex with further temperature increase due to organic phase degradation.     

Deoxy-nitrosugars. 16th Communication. Synthesis of N-acetyl-4-deoxyneuraminic acid

The synthesis of 5-acetamido-4-deoxyneuraminic acid ( 1 ) is described. Acetylation of a mixture of the epimeric triols 4 and 5 gave the tetraacetates 7 and 8 (Scheme 1). Ozonolysis of a mixture of these acetates followed by base-promoted β-elimination led to the (E) -configurated α,β-unsaturated keto ester 10 , which was hydrogenated to give the saturated keto ester 11 . Saponification of 11 and hydrolytic removal of the benzylidene group followed by anion-exchange chromatography gave the 5-acetamido-4-deoxyneuraminic acid ( 1 , Scheme 1 and 2). De-O-acetylation (NaOMe/MeOH) of the keto ester 11 gave a mixture of the tert-butyl ester 12 and the methyl ester 13 , which were converted to tert-butyl N-acetyl-4-deoxyneuraminate ( 14 ) and to methyl N-acetyl-4-deoxyneuraminate ( 15 ), respectively. Hydrogenolysis of the benzylidene acetal 11 followed by de-O-acetylation gave the pentahydroxy ester 16 .