摘要:

AbstractIn studying the mechanism of the oxidation coupling polymerization of 2,6‐dimethylphenol, the effect of the copper counter‐ion was also investigated. This polymerization is catalyzed by copper(II)‐amine complexes. In these experiments, tmed*** is used as amine ligand. The counter‐ions were divided into strongly coordinating (viz. Cl−and Br−), weakly coordinating (viz. NO3−) and non‐coordinating counter‐ions (viz. ClO4−, CF3SO3−and BF4−).Catalyst solutions, prepared from copper salts with coordinating counter‐ions, yield very high maximum activities at OH/Cu ≈︁ 1, whereas the non‐coordinating counter‐ions give much lower maximum reaction rates at OH/Cu ≈︁ 2 or higher. Copper‐amine complexes of weakly and non‐coordinating counter‐ions were found to yield hydroxo‐bridged complexes with a very low catalytic activity under all conditions. Due to this stable dihydroxo bridge and the absence of coordinating counter‐ions (Cl−, Br−) to replace them, only phenolate anion can readily attack this complex and occupy a coordination site at the expense of a coordinated OH−ion, thus explaining the optimum activity at an OH/Cu ratio of 2 or higher. However, even under these conditions, catalytic activity of these complexes is still low compared to catalysts prepared from CuCl2or CuBr2, further suggesting that preformation of a chloro‐bridged or bromo‐bridged copper complex is beneficial. Thus, these experiments indicate that the active catalyst, or its precursor, is the chloro‐bridged, or bromo‐bridged, dinuclear copper complex with hydroxide acting as a co‐catalyst required for the formation of strongly coordinating phenolate anions.Although large differences in reactivity were observed, the product composition,i.e.the fraction polymer (by C‐O coupling) and diphenoquinone (DPQ, undesired side‐product formed by C‐C coupling), was not affected by the counter‐ion used,viz. 3.5% DPQ. These results are a further indication

ISSN:0165-0513    

DOI:10.1002/recl.19891080702

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractColourimetric and magnetic measurements show that praseodymium soaps are ionic in nature and that the praseodymium ions are in trivalent state. Viscosity and colourimetric results show that the soap molecules do not aggregate below the CMC. Viscosity results have been interpreted in the light of well known equations proposed byEinstein, Vand, MoulikandJones‐Dol

ISSN:0165-0513    

DOI:10.1002/recl.19891080703

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe syntheses of cyclogentiotriose and cyclogentiotetrose peracetates by intramolecular cyclization of corresponding linear activated oligosaccharides are described.The optimization of cyclization of linear glucotetrose has been performed according to two different routes, (a) and (b). Route (b), which corresponds to activation of the anomeric carbon with dichloromethyl methyl ether/boron trifluoride etherate reagent, prior to removal of the O‐6 trichloroacetyl ester group with ammonia, proved to be superior, in terms of yield, to route (a

ISSN:0165-0513    

DOI:10.1002/recl.19891080704

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractA low‐temperature ESR study on electron‐capture radicals in X‐irradiated alkyl/ phenylphosphine chalcogenides is presented. In general, exposure of solid R(3‐n)PhnPX derivatives (R = alkyl, Ph = phenyl, X = S, Se,n= 1, 2) to X‐rays gave ESR spectra assigned to the corresponding radical anions, in which the unpaired electron is located in an antibonding P‐X σ* orbital. For two of the compounds studied (Me2PhPSe and MePh2PSe), however, no phosphoranyl radicals could be observed. For methylphenyl‐n‐propylphosphine selenide, a single‐crystal ESR analysis of the σ* radical anion is presented, giving detailed information on its electronic and geometric structure. It is found that the unpaired electron resides in a PSe anti‐bonding σ* orbital, whose direction almost parallels the parent PSe bond. Aspects of radiation damage mechanisms and phosphoranyl radical formation in phosphine c

ISSN:0165-0513    

DOI:10.1002/recl.19891080705

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe synthesis of 6‐demethoxy‐N‐formyl‐N‐northebaine (5) and its Diels‐Alder reactions with methyl vinyl ketone and nitroethene are described.N‐Demethylation of 6‐demethoxythebaine (3) with diethyl azodicarboxylate, followed by hydrolysis, gave 6‐demethoxy‐N‐northebaine (4) which wasN‐formylated with ethyl formate in DMF to give5, using “Ketjencat LA‐LPV Steamed” as a catalyst.Reaction of5with methyl vinyl ketone using microwave heating gave the expected 7α‐acetyl‐6α,14α‐ethenoisomorphinan9by direct crystallization from the reaction mixture. On the other hand, Diels‐Alder reaction of5with nitroethene afforded the 7α‐nitro‐6α,14α‐ethenoisomorphinan12as a minor product (10%). The major products were 8α‐nitro‐6α,14α‐ethenoisomorphinan (10) (50%) and 8β‐nitro‐6β, 14β‐ethenomorphinan (11) (30%). The structure of the new adducts was elucidated by1H NMR.Factors which may influence the course of the Diels‐Alder reaction of morphinan‐6,8‐dienes are discussed. The surpr

ISSN:0165-0513    

DOI:10.1002/recl.19891080706

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe new complex PdIPh(tmeda) (1) (tmeda = Me2N(CH2)2NMe2) was prepared by oxidative addition of iodobenzene to {bis(dibenzylideneacetone)}palladium(0) in the presence of tmeda and has been characterized by NMR spectroscopy and X‐ray crystallography. Treatment with MeLi affords the remarkably stable mixed diorgano species PdMePh(tmeda) (2). Both (1) and (2) are useful precursors to other organopalladium species by ligand exchange reaction

ISSN:0165-0513    

DOI:10.1002/recl.19891080707

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19891080708

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19891080709

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19891080712

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19891080713

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY