摘要:

AbstractThe advantages of radical reactions for Organic Synthesis are summarised. Based on the idea of the disciplined radical, it is now possible to design radical reactions which afford a good yield of a single desired product. The system needs to contain a disciplinary group. In the case of radical reactions involving tin hydrides, it is the weak tin‐hydrogen bond that is the disciplinary group. For the esters of thiohydroxamic acids, the disciplinary group is the thione function. Examples are given. Recent work has involved the design of stereospecific radical reactions. The hindrance around one chiral center is used to control the formation of the second. The ketal of (+)‐ (2R, 3R) tartaric acid gives excellent stereospecificity (≌24:1) with retention of configur

ISSN:0009-4536    

DOI:10.1002/jccs.198800037

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractSubstitution‐inert metal complexes, [Co(edda)(H2O)2]+, (Co(edda)(en)]+, [Co(edda)(dmen)]+, [Co(en)2‐(gly)]2+, [Co(en)2(acac)]2+, and [Co(trien)(gly)]2+in their nitrate salt solutions are used as eluents in nonsuppressed cation chromatography (where edda = ethylenediamine‐N,N′‐diacetic acid, en = ethylenediamine, dmen = N,N′‐dime‐thylethylenediamine, gly = glycine, acac = acetylacetone, and trien = triethylenetetraamine). It is found that all the mono‐ and di‐valent charged complexes can be used to separate alkali and alkaline earth metal cations, respectively. The separations for monovalent cations are sometimes comparable to those using ultrapure HNO3solutions. However, the divalent Ca2+and Sr2+ions cannot be resolved using the metal complex eluents. On the other hand, a selected, direct non‐suppressed IC separation of zinc(II) and cadmium(II) ions is demonstrated for the first time using a substitution‐inert metal complex eluent and a conductivity detector. Comparisons of these eluents with those reported previously, i. e. HNO3and ethylenediammonium salt solution are made and explanations are proposed to account for the different selectivities observed where possible. The future development of this technique is

ISSN:0009-4536    

DOI:10.1002/jccs.198800038

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractComplexes (η4‐PhCH=CHCR=NPh)Fe(CO)3, where R=H(1a) and CH3were synthesized in excellent yield from the reaction of the corresponding α,β‐unsaturated ketimines with excess Fe2(CO)9. Reaction of la with (Ph)2CHLi and (CH3)2(NC)CLi at −78°C or ambient temperature followed by acid quenching gavetrans‐PhCH=CHCHRNHPh, where R=CHPH2and C(CH3)2CN, respectively, in good yield. In the presence of 1 atm. of CO the reaction of 1a with (CH3)2(NC)CLi, followed by CuCl2oxidation resulted in the formation of a carbamyl choride,trans‐PhCH=CHCH[C(CH3)2CN]N(Ph)COCl. This species was converted to a carbamate compoundtrans‐PhCH=CHCH[C(CH3)2‐ CN]N(Ph)COOCH3in MeOH in th

ISSN:0009-4536    

DOI:10.1002/jccs.198800039

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractBy controlling the current density, pH and temperature of the electrodepositing iron‐zinc bath, various compositions of electrodeposited Fe1‐xZnx(0.95>x>0.15) alloys on Al‐foil have been prepared. The electronic state, intermetallic phases and magnetic hyperfine interactions have been studied by means of57Fe Mössbauer spectroscopy at 298K for these electrodeposited Fe‐Zn alloys. The isomer shifts obtained from the Mössbauer spectral of the alloys increased with increasing Zn content. An alloy containing above 50% Fe, exhibits a linear dependence of the internal magnetic field, Hin, on the Z

ISSN:0009-4536    

DOI:10.1002/jccs.198800040

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractAn aqueous PVA‐Cu2+solution at pH = 3 is in the hydrated form and becomes green at pH ⩾ 6 with a decrease in viscosity. The structure of the copper ion is suggested to be that of a polynuclear complex at pH>6. For the green solution the polynuclear chains of the copper complex are believed to be surrounded by the PVA chains with the hydrophobic backbones facing toward the inside and the hydrophilic OH groups oriented toward the outside facing the bulk water. The proton spin‐lattice relaxation rate 1/T1pand the spin‐spin relaxation rate 1/T2of CH and CH2in PVA and H2O for aqueous PVA‐Cu2+solutions at pH = 3, can be explained by the two site exchange model in the region of the fast exchange limit. The dipolar correlation time τcis dominated by the reorientational process with a dipolar correlation time of 2.11 × 10−11s. When the pH rises from pH=3 to pH=12.5, the variation of 1/T1p and 1/T2p of CH and CH2in PVA with Cu2+ion concentration in aqueous PVA‐Cu2+solution at pH=12.5 can be explained in terms of the relaxation by an inclusive model of the polynuclear copper complex and PVA. Furthermore, the frequency (or field) dependence of 1/T1p, 1/T2p of CH in PVA for aqueous PVA‐Cu2+solution at pH = 12.5 suggests that the dipolar relaxation is dominated by the electron‐spin relaxation with the electron spin relaxation time T1e= 1 ˜ 2 × 10−10s. The invariance of 1/T1p and 1/T2p of H2O with the variation of the Cu2+ion concentration in aqueous PVA‐Cu2+solution at pH = 12.5 supports the hypothesis that the water is not dire

ISSN:0009-4536    

DOI:10.1002/jccs.198800041

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe reaction mechanism of methanol conversion to hydrocarbons on HZSM‐5 zeolite was studied. From the selectivity plots of products in an integral fixed‐bed flow reactor, paraffins were classified as primary and secondary stable products, light olefins as primary unstable products, aromatics as primary and secondary unstable or stable products. The results of the14C‐labelled methanol reaction indicated that the C1–C5surface intermediates generated by dimethyl ether / methanol equilibrium gave paraffins and olefins at 300°C. The concentration of intermediates and adsorbed methanol on ZSM‐5 decreased with increasing temperature. The distribution of radioactivity showed that propylene played an important role in the autocatalysis of th

ISSN:0009-4536    

DOI:10.1002/jccs.198800042

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe title compound is functionalized by a series of reactions to yield derivatives in the forms of hydroxides, ketones, ketals, lactones, etc. Their structures are analyzed by NMR spectroscopy.

ISSN:0009-4536    

DOI:10.1002/jccs.198800043

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractA new process for the synthesis of (±)‐α‐vetispirene (1) starting from 2,4‐dimethyl‐3‐carbethaxycyclohexene (2) is described. The key steps include the stereoselective alkylation of2with ethyl 4‐bromo‐butyrate to yield ethyl 4‐(2,6‐dimethyl‐1‐carbethoxycyctohex‐2‐enyl)‐bytyrate (3) and spiroannulation of3by Dieckmann condensation to give 2‐carbethoxy‐6,10‐dime

ISSN:0009-4536    

DOI:10.1002/jccs.198800044

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractA new aporphine alkaloid was isolated from the stem bark ofCananga odorata Hook. f. et Thomson(Annonaceae). The structure of this alkaloid has been established as ushinsunineN‐oxide (6aS, 7R) (1) on the basis of spectroscopic evidences and by chemical transformatio

ISSN:0009-4536    

DOI:10.1002/jccs.198800045

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractFive Taxane derivatives were isolated fromTaxus mairei.Their structures were determined by spectroscopic methods and their physical constants were identical with the literature values. These are Taxa‐4(20), 11‐diene‐2α, 5α, 7β‐tetrol‐5α, 7β, 10β‐triacetate‐2α‐α‐methylbutyrate(I); Taxa‐4(20), 11‐diene‐2α, 5α, 9α, 10β, 13β‐pentol‐2α, 9α, 10β, 13α‐tetraacetate‐5α‐cinnamate(II);Taxa‐4(20), 11‐diene‐5α, 7β, 9α, 10β, 13α‐pentol‐pentaa

ISSN:0009-4536    

DOI:10.1002/jccs.198800046

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY