Synthese von 3-(2-Carboxy-4-Pyridyl)- und 3-(6-Carboxy-3-pyridyl)-DL-alanin

Synthesis of 3-(2-Carboxy-4-pyridyl)-and 3-(6-Carboxy-3-pyridyl)-DL-alanine As starting materials for potential photochemical approaches to betalaines C(R = COOH) and to muscaflavine F(R = COOH), β-(2-carboxy-4-pyridyl)- and β-(6(carboxy-3-pyridyl))-DL-alanine ( A and D with R = COOH or 4 and 11 ), respectively, were prepared (Scheme 1). The synthesis of 4 (= A, R = COOH) started with the 2-[(4-pyridyl)methyl]malonate 1 and proceeded via the N-oxide 2 , cyanation and hydrolysis (Scheme 2). Amino acid 11 was obtained from (3-pyridyl)methyl-bromide ( 6 ) via the malonate 7 by an analogous sequence of reactions (Scheme 3).     

Meso-ionic compounds. XI,photochromic 4-halogeno-3-(3-pyridyl)sydnones

Halogenation of 3-(3-pyridyl)sydnone with N-halosuccinimides in chloroform afforded the 4-halogeno-3-(3-pyridyl)sydnones where X = CI, Br, I. The 4-chloro- and 4-bromopyridylsydnones were photochromic. 3-(3-Pyridyl)sydnone was obtained in both high yield and purity by dehydration of N-nitroso-N-(3-pyridyl)glycine with trifluoroacetic anhydride.     

Pyridine-substituted hydroxythiophenes. V. Preparation of 5-(2-, 3-and 4-pyridyl)-2-hydroxythiophenes

5-(2-, 3- and 4-Pyridyl)-2-t-butoxythiophenes have been prepared in very good yields by Pd(0) catalyzed cross-coupling of the three isomeric bromopyridines with 5-trimethylstannyl-2-t-butoxythiophene derived from 2-bromothiophene via 2-t-butoxythiophene. Dealkylation of 5-(2-, 3- and 4-pyridyl)-2-t-but-oxythiophenes with boron trifluoride etherate in dichloromethane at room temperature led to predominant formation of rearranged products, 5-(2- and 3-pyridyl)-3-t-butyl-3-thiolene-2-ones, together with a small amount of 5-(2- and 3-pyridyl)-2-hydroxythiophenes as a mixture of two tautomeric keto forms in the case of the 2-pyridyl and the 3-pyridyl isomers, and exclusive formation of rearranged product in the case of the 4-pyridyl isomer. However, dealkylation of 2-methoxy-5-(2-, 3- and 4-pyridyl)thiophenes, prepared similarly to the 5-(2-, 3- and 4-pyridyl)-2-t-butoxythiophenes, with boron tribromide under the same reaction conditions as above resulted exclusively in the tautomeric mixture of 5-(2- and 3-pyridyl)-3-thiolene-2-ones and 5-(2- and 3-pyridyl)-4-thiolene-2-ones in the case of the 2-pyridyl and 3-pyridyl isomers. In the case of the 4-pyridyl isomer polymerization took place.     

Stereoselektive reduktive Dimerisierung von α-Cyan-β-(4-pyridyl)acrylsäurederivaten

Stereoselective Reductive Dimerisation of α-Cyano-β-(4-pyridyl)acrylic Acid Derivatives Catalytic hydrogenation of the α-substituted β-(4-pyridyl)acrylonitriles 3 and 4 (see Scheme 3) yields via stereoselective reductive dimerization the substituted cyclo-pentene derivatives 7 and 8 (see Scheme 4 and 5) instead of the expected dihydro-products 5 and 6 . The mechanism of this reaction is discussed. The structure and relative configuration of 10 have been established by X-ray single crystal analysis.     

Partialsynthesen und Reaktionen von Abietanderivaten (Lanugonen) aus Plectranthus lanuginosus und verwandten Verbindungen

Partial Syntheses and Reactions of Abietanoid Derivatives (Lanugones) from Plectranthus lanuginosus and of Related Compounds Interconversions by partial syntheses of several lanugones establish their absolute configuration at C(15). Unexpected reactions exemplify the unique reactivity of these abietanoic diterpenes, - Lanugone O ( 4 ) was prepared in several steps from (15S)-coleon C ( 8a ; Scheme 2) thus establishing its (15S)-configuration. One of the intermediates, the 12-O-acetyl-6-oxoroyleanone 12 , through acetyl-migration sets up an equilibrium with the vinylogous quinone 13 (Scheme 3). - The chirality at C(15) in the dihydrofuran moiety of lanugone Q ( 16 ) was proven by acid-catalyzed conversion of lanugone O ( 4 ) to 16 . - Instead of the usual nucleophilic attack shown by quinomethanes, lanugone L (1 ) is electrophilically substituted at C(7) by acetic anhydride/pyridine (Scheme 1). - In a homosigmatropic [1,5]-H-shift, lanugone G ( 17 ) in solution is converted to the corresponding allyl substituted royleanone 18 (Scheme 4). - Methanolysis of lanugone J ( 19 ) leads to the expected royleanone 20 having the 2-methoxypropyl side chain ( Scheme 5 ). Similar reactions were found in acetolytic reactions. However, treatment-of spirocoleons with SOCl₂/DMF produces mainly 12-deoxyroyleanones with allyl- and 2-chloropropyl groups, i. e. 19 → 26 and 27 ; 28 → 29 . The possible natural occurrence of these compounds is emphasized.     

Rearrangement of N-(3-pyridyl)nitramine

Contrary to other N-(pyridyl)nitramines, the title compound cannot be rearranged to 3-amino-2-nitropyridine or other isomers. Hypothetical products of its transformation under influence of concentrated sulphuric acid, viz. 3-hydroxypyridine, 3,3′-azoxypyridine and 3,3′-azopyridine, were obtained from 3-nitro- and 3-aminopyridine in oxidation and reduction reactions. N-(3-Pyridyl)nitramine was prepared and rearranged in concentrated sulphuric acid. 3-Hydroxypyridine and 3,3′-azoxypyridine were isolated from the reaction mixture, other products were identified by the HPLC and GCMS methods. The results indicate that N-(3-pyridyl)hydroxylamine is an intermediate formed from N-(3-pyridyl)nitramine under the influence of concentrated sulphuric acid. The reaction path, leading to the final products, is discussed in context of the mechanism of nitramine rearrangement.     

Synthesis,polarography and herbicidal activity of quaternary salts of 2-(4-pyridyl)-1,3,5-triazines, 5-(4-pyridyl)pyrimidine, 2-(4-pyridyl)pyrimidine and related compounds

2-(4-Pyridyl)-1,3,5-triazine, 2-(4-pyridyl)-4-methyl-1,3,5-triazine, 2-(4-pyridyl)-4,6-dimethyl-1,3,5-triazine and 2-(4-pyridyl)pyrimidine have been prepared by modification of established triazine and pyrimidine syntheses. These compounds and some of their relatives have been converted to quaternary pyridinium salts. The polarographic reduction potentials of the salts in aqueous solution are pH dependent. The activity of the salts as post-emergent herbicides is reported.     

Analytical properties of di(2-pyridyl)methylene 2-furoylhydrazone and spectrophotometric determination of trace amounts of iron

Summary The synthesis and analytical properties of di(2-pyridyl) methylene 2-furoylhydrazone (DPFH) are described. The solubility, spectral characteristics, andpK values are reported, as well as the absorptivity of metal chelates formed. The reaction between iron and DPFH has been studied by spectrophotometry. The green 12 iron: DPFH complex (=8.4×103l·-mole^–1·cm^–1 at 620 nm) is formed at pH 5.3–11.3. The effect of interferences has been studied and the method applied to the determination of iron in cement, with good results.

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Di-(2-pyridyl)methylen-2-furoylhydrazon als analytisches Reagens zur spektrophotometrischen Bestimmung von Eisenspuren

Zusammenfassung Synthese und analytische Eigenschaften von Di(2-pyridylmethylen-2-furoylhydrazon wurden beschrieben. Die Löslichkeit, die Spektraleigenschaften, diepK-Werte und die Absorptivität seiner Metall-Chelate wurden angegeben. Der grüne 12-Komplex mit Eisen bildet sich bei pH 5, 3-11, 3. Störfaktoren wurden untersucht und die Eisenbestimmung in Zement beschrieben.

     

Spectrophotometric determination of iron(II) by extraction of its ion associated complex with 3-(4-phenyl-2-pyridyl)-5,6-diphenyl-1,2,4-triazine and tetraphenylborate into molten naphthalene

Summary A new spectrophotometric method for the determination of iron (II) after extraction of its 3-(4-phenyl-2-pyridyl)-5,6-diphenyl-1,2,4-triazine complex with tetraphenylborate anion into molten naphthalene has been developed. The optimum pH range for the extraction is 6.0–7.0. The solid naphthalene containing the iron(II) associated complex is separated by filtration and dissolved in DMF. Beer's law is obeyed in the concentration range 1.0–16µg of iron(II) in 10 ml of DMF solution. The molar absorptivity and sensitivity are 2.85×10⁴ 1 mol^–1 cm^–1 and 0.00194g cm^–2, respectively. The interference of various ions has been studied. Conditions have been satisfactorily applied for the determination of iron in standard reference materials and practical samples and results compared with other standard colorimetric procedures.

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Spektrophotometrische Bestimmung von Eisen(II) nach Extraktion seines Ionen-Assoziations-Komplexes mit 3-(4-Phenyl-2-pyridyl)-5,6-Diphenyl-1,2, 4-Trazin (PPDP) und Tetraphenylborat mit geschmolzenem Naphthalin

Zusammenfassung Eine neue spektrophotometrische Methode zur Bestimmung von Fe(II) nach Extraktion des mit PPDT und Tetraphenylborat gebildeten Komplexes mit geschmolzenem Naphthalin wurde ausgearbeitet. Das optimale pH für die Extraktion liegt zwischen 6,0 und 7,0. Das feste Naphthalin mit dem Fe(II)-Assoziat-Komplex wird durch Filtration abgetrennt und in DMF gelöst. Das Beer'sche Gesetz wird zwischen 1,0 und 16g Fe(II) in 10 ml DMF-Lösung erfüllt. Die molare Absorptivität beträgt 2,85×10⁴l·mol^–1·cm^–1; die Empfindlichkeit beträgt 0,00194g·cm^–2. Die störende Wirkung verschiedener Ionen wurde untersucht. Das Verfahren eignet sich für die Untersuchung von Standard-Referenzproben. Es wurde mit anderen Standard-Methoden verglichen.

     

Syntheses and structural characterizations of 2-pyridyl(N/O)spirocyclotriphosphazene derivatives

The Cl exchange reaction of hexachlorocyclotriphosphazene, N₃P₃Cl₆ (1), with one equimolar amount of sodium salt of N/O donor type bidentate ligand containing a 2-pyridyl pendant arm (2) afforded, regioselectively, the partly substituted 2-pyridyl(N/O)spirocyclotriphosphazene (3; with a yield of 65%) in THF. The reactions of 3 with excess pyrrolidine, morpholine and 1,4-dioxa-8-azaspiro[4,5]decane (DASD) led to the formation of the tetraamino-2-pyridyl(N/O)spirocyclotriphosphazenes (3a-3c) in high yields. Compound 3 also gave both tetrapiperidino (3d) and gem-bispiperidino (3e) products with excess piperidine. The structures of all the compounds were determined by elemental analyses, ESI-MS, FTIR, HSQC, HMBC and ¹H, ¹³C, and ³¹P NMR techniques. The crystal structure of 3c was identified by single crystal X-ray crystallography. Besides, the compound 3e had one stereogenic P atom, and its chirality was verified by ³¹P NMR spectroscopy in the presence of (S)-(+)-2,2,2-trifluoro-1-(9’-anthryl)-ethanol (CSA).     

Copper-catalyzed allylation of carbonyl derivatives using allyl(2-pyridyl)silanes

[reaction: see text] We have developed an efficient copper-catalyzed allylation of carbonyl derivatives using allyl(2-pyridyl)silanes, in which the strong directing effect of the 2-pyridyl group was observed. A useful synthesis and allylation of substituted allyl(2-pyridyl)silanes is also described.     

Convenient synthesis of 2-(2-pyridyl)-1, 3-diaminopropane,and its copper(II), nickel(II), and cobalt(III) complexes

Summary 2-(2-Pyridyl)-1, 3-propanediol was converted into the diacetate, which was then condensed with phthalimide. The product was hydrolyzed with hydrochloric acid to give 2-(2-pyridyl)-1, 3-diaminopropane. The free amine gave 12 complexes with copper(II), nickel(II), and cobalt(III), which were characterized spectroscopically and magnetically. Features of the amine as a ligand are discussed. A few related complexes were also studied.     

3-(2-Pyridyl)coumarins

3-(2-Pyridyl)coumarins were prepared by reaction of substituted salicylaldehydes and 2-pyridylacetonitrile. Benzylation, acylation, and aminomethylation of 7-hydroxy-3-(2-pyridyl)coumarin was studied. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 428–431, September–October, 2005.     

Rhodium(II)‐Catalyzed Inter‐ and Intramolecular Enantioselective Cyclopropanations with Alkyl‐Diazo(triorganylsilyl)acetates

The intermolecular cyclopropanation of styrene with ethyl diazo(triethylsilyl)acetate ( 1a ) proceeds at room temperature in the presence of chiral Rh^II carboxylate catalysts derived from imide‐protected amino acids and affords mixtures of trans‐ and cis‐cyclopropane derivatives 2a in up to 72% yield but with modest enantioselectivities (<54%) (Scheme 1 and Table 1). Protiodesilylation of a diastereoisomer mixture 2a with Bu₄NF is accompanied by epimerization at C(1) (→ 3 ). The intramolecular cyclopropanation of allyl diazo(triethylsilyl)acetate ( 8a ), in turn, affords optically active 3‐oxabicyclo[3.1.0]hexan‐2‐one ( 9a ) with yields of up to 85% and 56% ee (Scheme 3 and Table 2). Similarly, the (2Z)‐pent‐2‐enyl derivative 8d reacts to 9d in up to 77% yield and 38% ee (Scheme 3 and Table 3). In contrast, the diazo decomposition of (2E)‐3‐phenylprop‐2‐enyl and 2‐methylprop‐2‐en‐1‐yl diazo(triethyl‐silyl)acetates ( 8b and 8c , resp.) is unsatisfactory and gives very poor yields of substituted 3‐oxabicyclo[3.1.0]hexan‐2‐ones 9b and 9c , respectively (Table 3).     

Aromatische sigmatropische Wasserstoffverschiebungen in 2-Vinyl- und 2-Allylphenolen

Aromatic Sigmatropic Hydrogen-Shifts in 2-Vinyl- and 2-Allyl-phenols It is shown by deuterium labeling experiments that 2-vinylphenols, on heating at 142,5°, undergo aromatic [1,5]-H-shifts whereby o-quinone methides are formed as intermediates (Scheme 7). Thus, heating of 2-isopropenylphenol ( 6 ) in a D₂O/dioxane mixture leads to a rapid deuterium incorporation into the methylidene group of the isopropenyl moiety (Table 1) whereas its methyl group shows only a slow uptake of deuterium. The latter exchange process can be attributed to intermolecular reactions (Scheme 8). The quinone methide intermediates (e.g. 26 , Scheme 8) can be regarded as vinyl homologues of alkyl ketones. Therefore, 26 can exchange hydrogen in both methyl groups by an acid- and base-catalysed mechanism. Indeed, when 6 is heated in D₂O/pyridine or D₂O/CH₃COOD/dioxane, an almost statistical incorporation of deuterium into the methylidene and the methyl group of the isopropenyl moiety is observed (Table 3). As a consequence of thermally induced [1,5]-H-shifts, 2-(1′-propenyl)-phenols undergo rapid (E,Z) isomerization with first order kinetics on heating above 140° in decane solution. Activation parameters are given in Table 4. The observed primary +++++ H/D isotope effect of 3.3 in the (E,Z) isomerization of phenol 8 is in +++ment with intramolecular H/D-shifts in the rate determing step (Scheme 9 +++ Table 5). As expected aromatic sigmatropic [1,5]-H-shifts in 2-(1′-propenyl)-+++ are much faster than aromatic homosigmatropic [1,5]-H-shifts in 2-(2′-+++++)phenols (Scheme 1 and Table 6). The structurally comparable phenols +++ (Z)- 10 and (E)/(Z)- 14 (Scheme 3) show k([1,5])/k(homo-[1,5]) ≈ 2300 at ++++

1 A more detailed discussion in English is given in [1].

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Studies on condensed heterocyclic compounds II.Synthesis and antibacterial activity of 3-(4''''-pyridyl)-6-aroylamino/arylamino-S-triazolo[3,4-b]-1,3,4-thiadiazoles

3-(4′-Pyridyl)-4-amino-5-mercapto-1,2,4-triazole(1)reacted with aroyl isothiocyanates2a-1 to yield twelve novel 3-(4′-pyridyl)-6-aroylamino-S-triazolo[3,4-b]-1,3,4-thiadiazoles,4a-1.Triethylamine was necessary for the condensation of 1 with phenyl isothiocyanate(3)to give 3-(4′-pyridyl)-6-phenylamino-S-triazolo[3,4-b]-1,3,4-thiadiazole(6).The structures were confirmed bythe elemental and spectral analyses.Their antibacterial activity against B.Subtilis,E.Coli,E.aerogenes and S.aureus was observed preliminary.     

Helix-sense-selective copolymerization of phenyl[bis(2-pyridyl)]methyl methacrylate,diphenyl(2-pyridyl)methyl methacrylate and triphenylmethyl methacrylate with chiral anionic initiators

Optically active poly[triphenylmethyl methacrylate-co-phenyl[bis(2-pyridyl)]methyl methacrylate] (poly[TrMA-co-PB2PyMA], poly[diphenyl(2-pyridyl)methyl methacrylate-co-phenyl[bis(2-pyridyl)]methyl methacrylate] (poly[D2PyMA-co-PB2PyMA]), and poly[triphenylmethyl methacrylate-co-diphenyl(2-pyridyl)-methyl methacrylate] (poly[TrMA-co-D2PyMA]) were prepared by helix-sense-selective copolymerization with complexes of organolithium with (−)-sparteine [(−)Sp],(S, S)-(+)- and (R, R)-(−)-2,3-dimethoxy-1,4-bis(dimethylamino)butane [(+)- and (−)DDB], and (S)-(+)-2-(1-pyrrolidinylmethyl)pyridine [(+)PMP] as anionic initiators in toluene at low temperature. The copolymers obtained with (−)Sp and (+)DDB or (−)DDB complexes of organolithium showed low optical activity, but to [(+)PMP] complex with N,N′-diphenyleneamine monolithium amide [(+)PMP–DPEDA–Li)] was effective in synthesizing copolymers of high optical rotation ([α] about +320 to + 370°) which were comparable to those of corresponding homopolymers with one-handed helical structure. The optical rotations of poly[TrMA-co-PB2PyMA] and poly[TrMA-co-D2PyMA] were much more stable than that of poly(D2PyMA) or poly(PB2PyMA) in a solution of CHCl₃–2,2,2-trifluoroethanol (10 : 1, v/v) at 25°C, but optical rotation of poly[D2PyMA-co-PB2PyMA] slowly decreased with time in the same conditions. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2127–2133, 1998     

Special features of the electroreduction of alkyl-(2-pyridyl) sulfones

The electrochemical behavior of methyl- and tert-butyl-(2-pyridyl) sulfones at a mercury cathode is studied in anhydrous dimethylformamide (DMF) and water-organic (DMF, n-aliphatic alcohols) solvents by the methods of polarography and preparative electrolysis. It is found that the presence of a pyridine fragment in sulfones governs the diversity of electrode reactions including those that involve the material of cathode (mercury). The effect of the nature and composition of the organic component of a solvent on the direction of C-S bond cleavage is discussed. The aromatic heterocyclic fragment is selectively splitted out in the electrolysis of sulfone at a glassy-carbon cathode in a 60% EtOH-H₂O system containing LiCl, the supporting electrolyte salt.     

Ein einfacher Zugang zu 4-hydroxy-2,5-dimethyl-3(2H)-furanon (furaneol), einem Aromabestandteil von Ananas und Erdbeere

Furaneol®

1 Registered trade mark of Firmenich SA.

[4-hydroxy-2,5-dimethyl-3(2H)-furanone ( 1 )], a flavour component of pineapple and strawberry, has been prepared by a two-step synthesis starting with readily available 3-hexyne-2,5-diol. By the same method 4-hydroxy-5-methyl-3(2H)-furanone ( 2 ) and 2-ethyl-4-hydroxy-5-methyl-3(2H)-furanone ( 3a ) have been prepared from 2-pentyne-1,4-diol and 3-heptyne-2,5-diol, respectively.