摘要:

Polymethine Dyes with Light Absorption in the Near Infrared.There is a currently significant interest in days that absorb in the near infrared (NIR) region, These compounds are mainly used as laser days and photoreceptors of photodiode lasers. Many NIR dyes are of polymethinic structure such as polymethine cyanines and polymethine violenes. Knowledge about structure‐color relationships enables dyes of appropriate absorption features to be predicte

ISSN:0021-8383    

DOI:10.1002/prac.19913330202

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

Syntheses of Δ16‐17(Trialkylstannyl)steroids from 17‐Ketosteroids. II.The oxidation of the hydrazones of 17‐ketosteroids by iodine yields Δ16‐17‐iodosteroids (2,4). Starting with2or8(the 3‐tetrahydropyranylether of4) and lithium(tribu‐tyl)stannate, Δ16‐17(tributylstannyl)steroids (5,9) are synthesized. The reaction is catalyzed by electronrich complexes of nickel and palladium. In the course of side reactions Δ16‐olefines (6,10) and the „dimers”︁7and11, the products of a cross coupling of the Δ16‐17‐iodosteroids, and the Δ16‐17‐tributylstannylsteroids are obtained. The mechanisms of these side reactions and the influence of the solvent (THF, HMPA) are discussed.The tributylstannylsteroids are to be used as intermediates for the syntheses of ster

ISSN:0021-8383    

DOI:10.1002/prac.19913330203

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

The Reaction of 2‐Aminothiophene‐3‐carbonitriles with Heterocumulenes.The reaction of 2‐aminothiophene‐3‐carbonitriles (1) with phenyl isothiocyanate does not yield the expected thieno[2,3‐d]pyrimidine derivatives but the substituted dithieno‐[2′,3′:4, 3][2′,3′:8, 9]pyrimido[3, 4‐a]pyrimid‐7‐thiones (4). The compounds4also may be synthesized from1and thiophosgene. Analogously, from1and phenyl isocyanate the substituted dithieno[2′,3′:4, 3][2′,3′:8, 9]pyrimido[3, 4‐a]pyrimid‐7‐ones (9) arise in small yields. They are better obtainable from1and phosgene. Carbon disulphide react with1in pyridine to form a mixture of the thieno[2, 3‐d]pyrimid‐2, 4‐dithione (10) and the condensed compound4. The ratio of products depends on the substituents in the 4, 5‐position of1. The

ISSN:0021-8383    

DOI:10.1002/prac.19913330204

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

Mass Spectroscopy of Thiogibberellins.The results of the positive ion (electron impact, desorption electron impact, low voltage electron impact, positive ion desorption chemical ionization, — EI, DEI, LEI, PIDCI), as well as negative ion (electron attachment — EA) mass spectra of 4 different types of thio gibberellins 6–9 are compared, and the fragmentation pathways are disc

ISSN:0021-8383    

DOI:10.1002/prac.19913330205

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

AbstractSome organoselenium compound (1) were tested as catalysts for the oxidation of styrene to phenyloxirane (2) with hydrogen peroxide. Bis(2, 4‐dinitrophenyl) diselenide (12) was found most effective. A convenient method for the synthesis of phenyloxirane and its polysubstituted analogs was elaborate

ISSN:0021-8383    

DOI:10.1002/prac.19913330206

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

ISSN:0021-8383    

DOI:10.1002/prac.19913330207

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

AbstractSodium dihydridobis(2‐methoxyethoxo)aluminate (SDMA) is a suitable reducing agent for in situ generation of zerovalent nickel in a catalytic system nickel(II) 2, 4‐pentanedionate/phosphorus(III) ligand/reducing agent. Although generally less polymer is formed in the propadiene/propyne cooligomerization catalyzed by this system when the reducing agent is triethylaluminium, at molar ratios Al/Ni = 3 and P/Ni = 3 no polymer is formed with SDMA and the yield of oligomers is comparable to that obtained with triethylalumin

ISSN:0021-8383    

DOI:10.1002/prac.19913330208

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

AbstractBoth E‐ and Z‐(β‐stannylvinyl)phosphines are readily converted to the corresponding phosphine oxides by KMnO4in acetone. However, the less reactive oxidising agents MnO2and O2react selectively with only the E isomers. N.m.r. studies indicate that this may be due to interactions between the phosphorus lone pair and the triorganostannyl moiety in the Z‐isomer, which make the latter less susceptible to attack. N.m.r. parameters for the phosphines and their oxides are

ISSN:0021-8383    

DOI:10.1002/prac.19913330209

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

Acylation of N‐(2, 6‐Dimethylphenyl)‐α‐alanine Methylester with sp‐hybridized Carbonic Acid Derivatives.The title compound5reacts with isocyanates and isothiocyanates to yield the substituted imidazolidinones7and8, respectively, whereas with chlorosulfonyl isocyanate the open chained urea9is formed. Cyanation of5takes place with phenyl cyanate and cyanogene bromide. Consecutive reactions of the primary products are

ISSN:0021-8383    

DOI:10.1002/prac.19913330210

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY

摘要:

Synthesis of Novel Quinolone‐Chemotherapeutics. V. Methodical Investigations on the Synthesis of Quinolone Chemotherapeutics.The synthesis of 6, 7‐dihalogen‐N‐ethyl‐4‐oxo‐l, 4‐dihydroquinoline‐3‐carboxylic acids (3a,b) from 3, 4‐dihalogen‐anilines is a three‐step processes: (a) N‐ethylation, (b) reaction with ortho formic ester and Meldrum's acid, (c) intramolecular cyclization. An increase of the total yields in comparison with known methods is mainly connected with the third step. Here the Meldrum's method allows reactions in solution at temperatures ≥ 100°C. With application of special Lewis acids the 6, 7‐dihalogen‐substituted products are formed in relatively high yields (6, 7‐difluoro‐l‐ethyl‐4‐oxo‐1, ‐4‐dihydro‐quinoline‐3‐carboxylic acia (3a): 71%; 7‐chloro‐6‐fluoro‐1 ‐ethyl‐4‐oxo‐1, 4‐dihydro quinoline‐3‐carboxylic acid (3b): 60%) without impurities of the corresponding 5, 6‐dihalogen substituted isomers. Anhydrides (5) of 4‐oxo‐1, 4‐dihydro‐quinolone‐3‐carboxylic acids with dibromo and difluoro‐boric acid were synthesized and shown to facilitate the aromatic nucleophilic substitution. The k

ISSN:0021-8383    

DOI:10.1002/prac.19913330211

出版商:WILEY‐VCH Verlag GmbH    

年代:1991

数据来源: WILEY