摘要:

AbstractThe hydrolysis of a series of carboxy and methoxycarbonyl acetals, (Ib‐ IXband Ia‐ IXa) derived from substituted salicylic acids and benzaldehydes has been studied. A strong intramolecular acid catalysis has been observed in the hydrolysis of substituted carboxy acetals.The values of the Hammett ρ coefficients measuring the influence of substituents located in the aldehyde and phenol moieties are respectively −2.95 and + 0.93.Comparison with the ρ values obtained with methoxycarbonyl acetals indicates that the C–O bond is largely broken in the transition state. The Bronsted α coefficient for carboxy‐group catalysis is quite small, ∼0.2 ± 0.1, suggesting a low degree of proton transfer in the t

ISSN:0165-0513    

DOI:10.1002/recl.19760950102

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractThe mechanisms of decomposition and disproportionation of hydrazyl radicals and hydrazo compounds, derived from azo dyes, have been studied by flash photolysis, flow experiments and fluorescence spectrometry. The hydrazyl radicals undergo a combined decomposition and oxidation process, resulting in the formation of amines and iminoquinones, and regeneration of part of the amount of dye used in their preparation. Hydrazo compounds are formed upon further photo‐reduction of hydrazyl radicals, and decompose in a similar fashion as the latte

ISSN:0165-0513    

DOI:10.1002/recl.19760950103

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractProton NMR spectra of 1,8‐bis(dimethylamino)naphthalene and 1,8‐bis(diethylamino)‐naphthalene (MPS and EPS) solutions to which acetic acid or trifluoroacetic acid (TFA) has been added exhibit several characteristic features caused by proton exchange phenomena. In the presence of less than one mole of TFA per mole of diamine the protonated and unprotonated forms can be observed separately. The proton in the protonated amine resonates at unusually low field (∼20 ppm). When more TFA is added another proton signal at low field, between 18 and 12 ppm down field from TMS, is observed. The nature of the latter proton resonance is discussed. The proton in the amine is probably in a bridge between the two nitrogen atoms, since no magnetic inequivalence is observed for the four methyl or ethyl groups attached to the nitrogen. In the presence of acetic acid instead of TFA the proton in the amine molecule changes places with the other protons in the solution. From the temperature‐dependence of the spectra the activation energy for the exchange of D+between amine molecules has been estimated. The possible use of MPS as a probe for the investigation of hydrogen bonding phenomena in carboxylic acid solutions in non‐aqueous solvents i

ISSN:0165-0513    

DOI:10.1002/recl.19760950104

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractNitroxides 1 with a chloro or nitro substituent in the ß‐position can be generated by three methods: addition of radicals togem‐chloro nitroso‐ orgem‐nitro nitroso compounds (reaction 1), addition of chloro‐ or nitroalkyl radicals to nitroso compounds (reaction 2), and addition of atomic chlorine to nitrones (reaction 3). With nitrogen dioxide instead of chlorine, ß‐nitronitroxides cannot be obtained, because NO2adds to nitronesviaoxygen in a presumably charge‐controlled process. The presence of the chloro or nitro substituent in the ß‐position influences the unpaired spin density at nitrogen and thus lowers the nitroxide splitting constant.The ESR signals of the nitroxides1clearly show the hyperfine splittings caused by the ß‐substituent. In the presence of nitric oxide, ß‐chloronitroxides cannot be detected and ß‐nitronitr

ISSN:0165-0513    

DOI:10.1002/recl.19760950105

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

Abstract13C‐NMR data of several 3‐mono‐ and 3,6‐di‐substituted pyridazines, 3‐, 4‐ and 6‐mono‐ and 3,6‐di‐substituted pyridazine 1‐oxides and 4‐nitro‐3,6‐disubstituted pyridazine 1‐oxides are reported.13C substituent effects of some substituents in the 3‐, 4‐ and 6‐position of the pyridazine ring and that of theN‐oxide function are calculated. The13C‐NMR spectra of the σ‐adducts of 4‐nitro‐3,6‐disubstituted pyr

ISSN:0165-0513    

DOI:10.1002/recl.19760950106

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractAcid‐catalysed cyclization of 1‐(3,5‐dihydroxy‐4‐methoxybenzyl)‐N‐formyl‐1,2,3,4,5,8‐hexahydro‐6‐methoxyisoquinoline (2c), where the benzyl group is symmetrically substituted, gaveN‐formyl‐2‐hydroxynordihydrothebainone (4c) exclusively. The 2‐hydroxyl substituent could be removed selectively in high yield,viathe 1‐phenyltetrazol‐5‐yl ether (4d), to yieldN‐formylnordihydrothebainone (4e). (‐)‐N‐Formylnordihydrothebainone (4e) was reduced to (‐)‐dihydrothebainone (4a). The conversion of4ato codeine (

ISSN:0165-0513    

DOI:10.1002/recl.19760950107

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

Abstract1‐Alkynyl sulfides R1C≡C‐S‐R21are easily converted with a copper(I) hydride complex in tetrahydrofuran intocis‐1‐alkenyl sulfides R1CHCH‐S‐R22in yields>90%. Treatment of compounds1with LiAlH4in the same solvent leads to the isomerictrans‐1‐alkenyl sulfides R1CH CH‐S‐R23i

ISSN:0165-0513    

DOI:10.1002/recl.19760950108

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

摘要:

AbstractThe reaction of chlorosulfines [R‐C(Cl)SO with R beingp‐CH3C6H4S, Cl andp‐ClC6H4] withp‐toluenesulfinate leads to products in which the CSO function is replaced by a CH2group. The first step in the reaction is a substitution of chlorine by sulfinate. Subsequent attack of the sulfinate at the sulfine sulfur atom produces sulfinyl sulfones which upon hydrolysis provide the apparent reduction products. Substantiation of the suggested reaction sequence was achieved by reaction of a sulfone sulfine with sulfinate and isolation of one of the propose

ISSN:0165-0513    

DOI:10.1002/recl.19760950109

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19760950101

出版商:WILEY‐VCH Verlag    

年代:1976

数据来源: WILEY