摘要:

AbstractA convenient, high yield “dry” method of synthesis of monomeric N‐methyleneanilines (6a—i) and the characterization of the products by m.s.,1H‐ and13C‐n.m.r. and i.r. are reported, improving previous procedures and describing new compounds. It appeared that the existence of monomeric N‐methyleneanilines is strictly related to the presence of enough steric hindrance to oligomerization by substituents in ortho positions. Moreover, some addition products of formaldehyde to an amine and its corresponding imines are tentatively identified on the basis of the observed mass spectrum of the whole reaction mixture.The reaction products of formaldehyde with 2,6‐dimethylaniline (1a) provided an example of a mobile equilibrium between monomeric and

ISSN:0021-8383    

DOI:10.1002/prac.19883300202

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Abstract2‐Amino‐N‐heterocycles, such as 2‐aminopyridine7or 2‐aminobenzimidazole16as well as benzamidines19possessing a N‐(4‐nitrobenzyl)‐substituent react as N‐C‐N‐C‐synthons with formamide chlorides5, formamide acetals2or acetic anhydride (C1‐building blocks) with formation of imidazole compounds9,17or22, respectively in the presence of triethylamine. In some cases, intermediate N‐acetylation (20) or N‐formy

ISSN:0021-8383    

DOI:10.1002/prac.19883300203

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractAmbrosia maritima L. growing wild in central Sudan contained substantial amounts of two principal sesquiterpene lactones, ambrosin and damsin.1H,13C‐n.m.r.'s and X ray crystal analyses of these are discussed.Much interest and published results on the sesquiterpene plant isolates [1—9], the pseudoguiano‐lides, ensued from their pharmacological (eg. mollusicidal) activity of the compositae family and in particular the Ambrosinae. From the genus Ambrosia (Compositae, Heliantheae, subtribe Ambro‐sinae) several pseudoguianolides (eg. ambrosonolides) were isolated [7—12]. Recently, two pseudo‐guianolides, damsin and ambrosin were isolated fromA. Maritima L.sp. and other six more of these lactones were reported to occur in this species [4].The structures of these compounds were exclusively established through1H‐ and13C‐n.m.r. studies which in certain cases were by no means

ISSN:0021-8383    

DOI:10.1002/prac.19883300204

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

The Catalysis of the Co‐Oxidation of cis‐Oct‐4‐ene and n‐Butyric AldehydeThe co‐oxidation of cis‐oct‐4‐ene and n‐butyric aldehyde in the absence of catalysts, or in the presence of molybdenum and Co(acac)3, resp., was studied in dependence on the aldehyde/olefin ratio, on the temperature and other reaction conditions. Under the same conditions, the noncatalyzed co‐oxidation converted 50%, the MoO2(acac)2‐catalyzed one 68%, and the Co(acac)3‐catalyzed one 40% of the reacted olefin into the epoxide.The cis/trans‐epoxide ratio in the molybdenum‐catalyzed co‐oxidation was nearly 2 independent of the aldehyde/olefin ratio. In the non‐catalyzed co‐oxidation the cis/trans‐epoxide ratio depends linearly on the aldehyde/olefin ratio (cis/trans E. = 0,58 + 0,90 n °Al/n °O). From these dependences we can conclude that the homolytic mechanism of epoxide formation decreases and the polar mechanism (Priležaev‐reaction) increases with increasing aldehyde/olefin ratio.Optimization of the epoxide yields according to a Box‐Hunter experimental plan gave the following reaction conditions to yield 95% epoxide based on reacted olefin: 70°C, ΔnS/n °O= 0,49, n °K/n °O= 3,5 · 10−3, n °Al/n °O= 0,53. The co‐oxidation in the presence of other molybdenum catalysts of the chloro‐nitrosyl‐complex type and of the carbonyl‐com

ISSN:0021-8383    

DOI:10.1002/prac.19883300205

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Fotosensitized Fading of Azomethine DyesThe quantum yields of photofading of the azomethine dyes1a—hwere determined in the presence of the sensitizers benzophenone (B), michler's ketone (MK) and anthracen (A), in isopropanol and benzene. In isopropanol, excluding oxygen, the leuco dyes5are formed by benzophenone in high quantum yield (Φ BAr= 0.4). Photofading also takes place using Michler's ketone (Φ MKAr≅ 3 · 10−3) and anthracene (Φ AAr≅ 1 · 10−4), but5was not found. With benzophenone (Φ≅ 7 · 10−3), Micher's ketone (Φ MKO 2≅ 1 · 10−3) and anthracene (Φ AO 2≅ 1 · 10−4) as sensitizers the chromophore of1a—hwere destroyed, when oxygen was present. The photofading with benzophenone and Michler's ketone is a result of radicalic processes.Radical scavangers8and9, therefore, give a strong decrease of the quantum yield of photofading. The photofading in benzene corresponds to the results in isopropanol considering the lower potent

ISSN:0021-8383    

DOI:10.1002/prac.19883300206

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Reactions by Participating of Ylide‐Intermediates. III. On Preparation and Structural Elucidation of Spiro‐condensed TetrahydroindolizinesN‐(Fluroen‐9‐yl)‐pyridinium‐ and ‐isoquinolinium ylides (5) to (8) react with electrondeficit olefinic dipolarophiles under mild conditiones to give satisfactory to good yields of the corresponding spirocondensated tetrahydroindolizines (10) to (13). The structure and configuration of all isolated products were elucidated by spectroscopical methods, especially by 1 D‐ and 2 D1H‐n.m.r. The 1.3‐dipolar cycloaddition produced regiospecific cycloadducts. From the observed regiospecifity of unsymmetrically substituted olefines (9) can be concluded that the cycloaddition is HOMO(1.3‐dipole) — LUMO(dipolarophile) controlled. The olefines (9) add stereospecifically under retention of their configuration via exo as well as endo transition states. The nitrosubstituted ylides (6) and (8) produced always mixtures of diastereomeric c

ISSN:0021-8383    

DOI:10.1002/prac.19883300207

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Cyclofunctionalization of 2‐Allyl‐phenols with Sulfur Chlorides: Synthesis of 2‐Arylthiomethyl‐2,3‐dihydrobenzofurans by Reaction of 2‐Allyl‐ and 2‐Methallyl‐phenols, Respectively, and Arylsulfenyl ChloridesReactions of acetylamino substituted 2‐allyl‐phenols (1and2), and 2‐methallyl‐phenol (6), respectively, with different arylsulfenyl chlorides (3a—d) yield the products of a cyclofunctionalization 5‐ or 7‐acetylamino‐2‐arylthiomethyl‐2,3‐dihydrobenzofurans (4a–d) or (5a–d) and 7‐acetylamino‐2‐arylthiomethyl‐2‐methyl‐2,3‐dihydrobenzofurans (7a–d). The compounds7are the first examples of cyclofunctionalization of 2‐methallylphenols by means of sulfur chlorides. The identification of the products was carried out by ma

ISSN:0021-8383    

DOI:10.1002/prac.19883300208

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Synthesis and UV‐spectroscopic Characterization of Carbenium Ions on AerosilThe interaction of aerosil with various triphenylmethyl derivatives in the cationic vinyl polymerization in 1,2‐dichloroethane was studied. The adsorption of the triphenylmethylium ions onto aerosil surfaces strongly depends on both the type of substituents (R  CH3, OCH3, Cl, H and NO2) and the nature of the counter anion (SbCl6⊖, FeCl4⊖, SnCl5⊖, HSO4⊖, SO42⊖, F⊖, Cl⊖, Br⊖, CF3COO⊖, N3⊖and SCN⊖). The binding of the triphenylmethylium ions with aerosil occurs via nucleophilic anions such as halides. Counter anions derived from metal halides as MtXn+1⊖are not able bind on aerosil. Covalent compounds as triphenylmethyl halides are ionized by the acidic aerosil surface. The influence of substituents at the triphenylmethylium ion, the type of counter anions and the influence of water trace

ISSN:0021-8383    

DOI:10.1002/prac.19883300209

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Reactions of N‐(N′,N′‐Dialkyl(aryl)amino‐thiocarbonyl)benzimidoylchlorides with Potassium ThiocyanateThe treatment of the title compound N‐(amino‐thiocarbonyl)‐benzimidoylchloride1with potassium thiocyanate leads in dependence on the solvents (methanol, acetic acid, acetone) either to the 1,3,5‐thiadiazine‐2‐thione2a–dor to the ring opened isothiocyanate4a,b. In the case of methanol the N‐(amino‐thiocarbonyl)benzimidates were formed as by‐products.The structure of the products is confirmed by analytical data and by chemical transformations.2areacts with methyl iodide to form the 2‐methylthio‐6‐morpholino‐4‐phenyl‐1,3,5‐thiadiaziniumiodide3a. From4aand water the N‐(morpholino‐thiocarbonyl)benzamide5aarises. The reacti

ISSN:0021-8383    

DOI:10.1002/prac.19883300210

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

Quinolineanalogous Chalcones: Wittig Synthesis,13C‐N.M.R. Spectra and Estimation of σ‐Constants for the 2‐, 3‐ and 4‐Position of QuinolineThe Wittig type reaction of the quinolinealdehydes2a—cwith benzoylmethylentriphenylphosphorane (1) gives stereoselectively the E‐configurated quinolineanalogous chalcones3a—c. These compounds react with methyl iodide to the N‐methyl‐quinolinium salts4a—c. The complete13C‐n.m.r. analysis of3a—cis reported. From the chemical shift of the Cα‐signals and on the basis of a Hammett relationship σ‐constants were calculated for the 2‐, 3‐ and 4‐position of quinoline. These values are compared with those from kinetic measurements; the observed deviations are chiefly attributed to the exte

ISSN:0021-8383    

DOI:10.1002/prac.19883300211

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY