ISSN:0165-0513    

DOI:10.1002/recl.19811000602

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe hydrolysis of achiral and chiral esters by optically active poly(iminomethylenes), [R‐NC1c<2f. Poly(D‐carbylalanyl‐L–histidinol) shows enantioselectivity in the hydrolysis ofp‐nitrophenyl esters of

ISSN:0165-0513    

DOI:10.1002/recl.19811000603

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractCriegee rearrangement of 5α‐hydroperoxy‐6‐estren‐17‐one gave 6‐oxa‐B‐homo‐4,7‐estradien‐17‐one. This confirms that, in this rearrangement the alkenyl group has a greater migratory aptit

ISSN:0165-0513    

DOI:10.1002/recl.19811000604

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe photo‐induced oxidation of NADH and its model compound, 1‐benzyl‐1,4–dihydronicotinamide (BNAH), byN,N′‐dimethyl‐4,4′‐bipyridinium dichloride (methyl viologen: MV++) was studied in homogeneous and in micellar solution. In the overall, slightly endoergonic, reaction: NADH + 2 MV+ ++hv→ NAD++ 2 MV+• + H+the dihydropyridines lose a hydride equivalent via a stepwisee,H+,esequence in which only the initial one‐electron transfer requires photostimulation. It is shown that the singlet‐excited state of the dihydropyridine is the photoreactive intermediate in this initial electron transfer process and that the overall quantum yield depends critically on the ratio of the rates for ionic dissociation and back‐electron transfer in the encounter complex between this excited state and MV+ +molecules. This ratio can be influenced dramatically by changing the solvent medium. In aqueous solution (for NADH) and especially in anionic micellar solution (for BNAH) strong ground state association between MV++and the dihydropyridines occurs. Evidence for this association is provided by the appearance of a long‐wavelength charge transfer absorption, as well as by the large deviations from a Stern‐Volmer behaviour observed in the quenching of the dihydropyridine fluorescence by MV++. The ground state complexation appears to hamper ionic dissociation of the excited complex. This is evident from the low quantum yield for photooxidation of such systems, upon excitation of the dihydropyridine chromophore (365 nm), and the complete absence of such oxidation upon their excitation within the charge transfer absorption (546 nm). The data obtained are shown to allow for a complete thermodynamic analysis of the Gibbs free‐energy changes involved in loss of a hydride equivalent from a 1,4‐dihydropyridine via a stepwisee,H+,emechanism. The consequences of this analysis for the mechanism of reactions in which 1,4‐dihydropyridines transfer a hydride equivalent to various substrates

ISSN:0165-0513    

DOI:10.1002/recl.19811000605

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractThe dehydrogenation of methanol to formaldehyde in the absence of oxygen on a silver catalyst has been studied in a pulse system. The results suggest that the reaction is initiated on the surface of the catalyst, and that the formation of formaldehyde proceeds homogeneously in the gas phase. Formaldehyde yields per pass of more than 40% were obtained at 670°C with a contact time of 0.001 sec

ISSN:0165-0513    

DOI:10.1002/recl.19811000606

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractDeprotonatedN‐phenyl,N′,N′‐dialkylthiourea (PhtuR2) complexes of Cu(I) and Cu(II) have been isolated and the existence of a Cu(III) complex inferred from electrochemical measurements. The crystal structure of Cu(I)[(C6H5)NC(S)N[(C2H4)2O]] (space groupPl̄,Z= 24,a= 10.487(9),b= 28.961(8),c= 29.579(12) Å, α = 120.72(3), β = 103.69(5), γ = 83.14(4)°) revealed 4 hexameric units per unit cell. The metals form a distorted octahedron; the ligands are situated outside six of the faces of this octahedron. The copper coordination is threefold planar; a N atom is linked to one Cu and the S atoms to two Cu atoms. The Cu–Cu distances exclude strong metal‐metal interactions. ESR measurements on Cu(II)(PhtuBu2)2suggest a planar coordination around Cu with the N atoms intrans‐position. Cyclic voltamograms and differential pulse polarograms show the one‐electron oxidation, Cu(II)(PhtuR2)2→ Cu(III)(PhtuR2)2++ e. The Cu(III) complex is only stable on the electrochemical time scale

ISSN:0165-0513    

DOI:10.1002/recl.19811000607

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractA number of (dialkylamino)allenes2have been obtained in excellent yields and in a reasonable state of purity by isomerization of dialkyl‐2‐propynylamines1with potassiumtert‐butoxide in tetrahydrofuran or with the complext‐BuOK.t‐BuOH in hexamethylphosphoric triamide. Treatment of the 2‐propynylamines witht‐BuOK in dimethyl sulfoxide leads to equilibrium mixtures of the allenic amines2and dialkyl‐1

ISSN:0165-0513    

DOI:10.1002/recl.19811000608

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

摘要:

AbstractFluorination of 2‐bromo‐4,5‐dimethylphenol (1) with xenon difluoride, using boron trifluoride etherate as catalyst, gave 2‐bromo‐4,5‐dimethyl‐4‐fluorocyclohexa‐2,5‐dienone (2), 2‐bromo‐3,4‐dimethyl‐6‐fluorophenol (3) and 6‐bromo‐3,4‐dimethyl‐2‐fluorophenol (4). The products were isolated by means of preparative reverse‐phase HPLC an

ISSN:0165-0513    

DOI:10.1002/recl.19811000609

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19811000601

出版商:WILEY‐VCH Verlag    

年代:1981

数据来源: WILEY