摘要:

AbstractThe velocity of the hydrogen ion catalysed hydrolysis ofp‐nitrophenyl‐diazo‐methane (I) has been measured in H2OD2O mixtures, giving an isotopic αi= 0.49. The product isotope effectr= 5.1, determined from product analyses, combined with the (overall) solvent isotope effectkH/kD= 2.81, yields the primary kinetic isotope effect (kH/kD)I= 3.8, and the secondary kinetic isotope effect (kH/kD)II= 0.75. The CICH2COOH‐catalysed hydrolysis of I in H2OD2O mixtures gave a straight‐line plot ofkn/kHversusthe atomic fractionnof deuterium. With four carboxylic acids, as catalysts, values of about 4.3 for the kinetic (overall) isotope effects

ISSN:0018-019X    

DOI:10.1002/hlca.19720550102

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

Abstract1‐Acyl‐benzocyclobutenes (8, 9, 10), on heating in diluted decane solution at 175–185°, rearrange to the corresponding 3‐substituted isochromenes (11,

ISSN:0018-019X    

DOI:10.1002/hlca.19720550103

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractIn der Annahme, dass gewisse Aminosäuren im Gewebe von Säugetieren Vorläufer für «alkaloidische» Tetrahydro‐isochinoline sein könnten, wurden L‐Dopa und dessen zwei Monomethyläther mit Formaldehyd und Acetaldehyd kondensiert. Die absolute Stereochemie der erhaltenen 1‐Methyl‐substituierten Tetrahydro‐isochinoline wurde durchRöntgen‐Analyse einer Schlüsselverb

ISSN:0018-019X    

DOI:10.1002/hlca.19720550104

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractEs werden Versuche mit Tetrahydrofolsäure‐Modellsubstanzen unternommen, um die eigentliche Struktur des sogenannten «aktiven Formaldehyds» abzuklären. Alle Addukte der tetrahydrierten Substanzen mit Formaldehyd erweisen sich als Hydroxymethyl‐ und nicht als Imidazolidin‐Derivate. Ob das Additionsprodukt des Formaldehyds mit Tetrahydrofol‐säure ebenfalls ein Hydroxymethyl‐Derivat ist, bleibt n

ISSN:0018-019X    

DOI:10.1002/hlca.19720550105

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractBy adding thioethers to protonated quinones or quinone imines, hydroquinone sulfonium compounds are prepared in good yields. A mechanism running over carbenium ions is proposed.

ISSN:0018-019X    

DOI:10.1002/hlca.19720550106

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractThioethers reacted with protonated alkenes yield quantitatively alkylsulfonium salts. The rate of the reaction is dependent on the proton activity of the medium and characterized by a maximum which is determined by the protonation of the nucleophile (thioether). The reaction is following the rule ofMarkownikoff.

ISSN:0018-019X    

DOI:10.1002/hlca.19720550107

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractBy reaction of hydrated rare earths chlorides (M = La, Nd, Sm, Gd, Dy, Er, Yb, Y) with orthoformates, the following adducts have been prepared: MCl3· 4MeOH, MCl3·3EtOH (M = La, Nd, Sm, Gd, Yb), MCl4· 4 EtOH (M = Dy, Er, Y); adducts MCl3· 3iso‐PrOH have been prepared by successive action of methyl orthoformate and of 2‐propanol. The solubilities of these adducts in the corresponding alcohols at 25° (for the lanthanum adducts equally at 0 and 50°) are given. Two examples of the transsolvatation of these compounds, yielding adducts with weakligands, are

ISSN:0018-019X    

DOI:10.1002/hlca.19720550108

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractThe formation of chelate complexes between free radicals and closed‐shell metal ions is observed by ESR. spectroscopy. High resolution spectra of 1:1 complexes formed between the radical anion of glyoxal‐bis‐(N‐t‐butylimine) (GLIR) and Mg2+, Ca2+and Zn2+are completely analysed. The complexes formed in dimethoxyethane or tetrahydrofuran solutions are Ca(GLIR)+, Mg(GLIR)X, Zn (GLIR)X and Zn(GLIR)Y−2, where X = Cl−, Br−, I−, and Y = CN−, NCS−. The formation of the heterometallic, binuclear cyanide‐bridged complex Zn(GLIR)Fe(CN)63−is also described. Isotropic coupling constants are given for protons and14N in GLIR as well as for the metal nuclei and magnetic nuclei in the groups X and Y. Stabilities, structures and ESR. parameters of these radica

ISSN:0018-019X    

DOI:10.1002/hlca.19720550109

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractThe source of the instability ofD2h, bridged, diborane type geometries of ethanes is traced to a single molecular orbital,b2gor π* in symmetry. The energy of this orbital can be lowered, and the barrier to bridging accordingly decreased, by appropriately placed acceptor substituents. Low bridging barriers, relative to ethane, are predicted for cyclopentenyl cation, and cyano or nitro substituted ethanes

ISSN:0018-019X    

DOI:10.1002/hlca.19720550110

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY

摘要:

AbstractThe new reagent 2‐methoxy‐1,3‐dithiolane and cyclic ortho‐thioesters can be used in a new reaction of theFriedel‐Craftstype to introduce the corresponding aldehydic or ketonic thioacetal function directly into substrates containing an indole nucleus with free 2‐ or

ISSN:0018-019X    

DOI:10.1002/hlca.19720550111

出版商:WILEY‐VCH Verlag GmbH    

年代:1972

数据来源: WILEY