ISSN:0941-1216    

DOI:10.1002/prac.19943360802

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractCrystal and molecular structure of 2,6‐diphenyl‐4‐carboxypyrylium and 5,6,7,8‐tetrahydro‐8‐oxo‐2,4‐diphenyl‐1‐benzopyrylium perchlorates was solved. Analysis of our data and those retrieved form CSDB shows that for compounds with sp2carbon atoms in C4‐C41 bond exists very good relationships between lengths of this bond and bond angles at oxygen and at C4 atoms in the pyrylium ring. Good correlation exists too for two aromaticity indices and these bond lengths indicating mostly resonance effect of the substituent on the geometry

ISSN:0941-1216    

DOI:10.1002/prac.19943360803

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

Cycloadditions. 23. The Thermal Reactivity of S‐(1‐Naphthyl) and S‐(9‐Anthryl)2‐methyl‐2,3‐butadienethioatesHeating of the S‐(1‐naphthyl)esters of 2‐methyl‐2,3‐butadiene thioacid and of 2‐methyl‐4,4‐diphenyl‐2,3‐butadiene thioacid (3aresp.3b) furnishes mixtures of the Diels‐Alder products5a, band the cyclobutenone7and the naphthol derivative8, resp. The corresponding S‐(9‐anthryl) esters4a, bare not isolable; under the conditions of their synthesis (allenecarboxylic acids1au.b, 9‐thioanthrol2b, DCC and DMAP) they isomerise s

ISSN:0941-1216    

DOI:10.1002/prac.19943360804

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

AbstractDifferent electronic structures for the three 1,2‐naphthoquinone‐2‐diazide (NQD) chromophores in 2,3,4‐tri (1,2‐naphthoquinone‐2‐diazide‐5‐sulfonyl‐oxy)‐benzophenone were detected using1H NMR spectroscopy. The NQD substituent in the o‐position of the benzophenone is influenced by intramolecular through space interactions with the benzophenone part of the molecule. The change in the electronic structure is the reason for the obtained different photoreactivity of the o‐NQD chromophore compared with m‐NQD and p‐NQD. The relative quantum yields of photolysis are 0.3 (o

ISSN:0941-1216    

DOI:10.1002/prac.19943360805

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

Synthesis of ω‐Acetyl‐α‐methylenpolyene Carboxylic EstersThe α‐methylenpolyene carboxylic acids1and2are highly active against Gram‐positive bacteria. If this activity arises from an interference with the cell membranes, then an abrupt change in biological properties is to be expected with growing chain length of simple model compounds. To make these tests possible, we describe here the synthesis of a series of homologue esters of type40. Their synthesis was achieved by Wittig reactions of polyene αω‐dialdehydes6with acetyl‐methylentriphenylphosphoran5aand the protected carboxy‐methylmethylen triphe

ISSN:0941-1216    

DOI:10.1002/prac.19943360806

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

Photochemistry of Acylazides. VIII. Do Acylnitrenes React like 1,3‐Dipoles?The formation of three‐ ore five‐membered heterocyclic rings by the reaction of acylnitrenes with olefins depends on the electron density at the double bond. The generally expected formation of aziridines by a cheletropic reaction was observed by photolysis of aroylazides1in the presence of 2,5‐dihydrofuran2. But with enolethers3and4oxazolines were directly formed. This [3 + 2] cycloaddition is regiospecific. The cycloaddition is modestly stereoselective by steric hindrance within the cyclic enolether3b. Very small de‐values were found with chiral substituents in the acylazide13.The azide decomposition was also achieved by photoinduced electron transfer. The same cycloaddition products as obtained by direct photolysis of the azides were obtained via radical anions of the acylazide. Using Michler's ketone as electron donor in the triplet state the formation of isocyanate which diminishes the yield of cycloadducts can b

ISSN:0941-1216    

DOI:10.1002/prac.19943360807

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

摘要:

New Products by Ring Expansions of Solid 17‐Hydroxy‐20‐ketosteroids with Gaseous Hydrochloric AcidGaseous hydrogen chloride reacts directly with crystalline 17‐hydroxy‐20‐ketosteroids like 17α‐hydroxy‐progesterones (1, 5, 6, 8) to give enlargement of ring D. In addition to the known acyloine rearrangement, new reaction types are observed which give rise to the products of substitutive rearrangement with elimination of water, 16β‐Chloro‐(3) and 16α‐chloro‐16β‐methyl‐17‐oxo‐D‐homosteroids (7, 9) are formed stereoselectively. The drying agent magnesium sulfate may keep the reaction products solid. Mechanistic proof is provided spectroscopically (IR) and by the isolation of 17aβ‐hydroxy‐17aα‐methyl‐D‐homoandrost‐4‐ene‐3,17‐dione (2) and its conversion to 16β‐chloro‐17aβ‐methyl‐D‐homoandrost‐4‐ene‐3,17‐dione (3) wi

ISSN:0941-1216    

DOI:10.1002/prac.19943360808

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

ISSN:0941-1216    

DOI:10.1002/prac.19943360809

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

ISSN:0941-1216    

DOI:10.1002/prac.19943360810

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY

ISSN:0941-1216    

DOI:10.1002/prac.19943360811

出版商:WILEY‐VCH Verlag GmbH    

年代:1994

数据来源: WILEY