ISSN:0165-0513    

DOI:10.1002/recl.19961150202

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19961150203

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe title compounds (Scheme 1, Y = NMe2) were investigated by variable‐temperature NMR and/or by racemization of enantiomers enriched by liquid chromatography on microcrystalline triacetylcellulose. For several reasons, a dialkylamino and a dimethylcarbamoyl group were used, for the first time, as neighboring rotor substituents on a benzene ring. Barriers to rotations about their aryl‐nitrogen and/or aryl‐carbon bonds were determined and assigned (Table I). Correlated or uncorrelated motions of these groups are possible for amides11and19bearing in their 3‐positionstert‐butyl substituents which hinder the aryl‐nitrogen rotation. Uncorrelated rotations have been found for amide15(Figure 2) and thioamide8which have the less voluminous bromine atom in their

ISSN:0165-0513    

DOI:10.1002/recl.19961150204

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractAn efficient procedure for the glycosidation of D‐fructose and D‐glucose catalyzed by iodine is described. The reaction yields mainly alkyl glycofuranosides. Treatment of inulin under similar conditions leads to inter‐glycosidic bond cleavage and to formation of alkyl D‐fructofuranosides. The reaction conditions are particularly mild and relatively se

ISSN:0165-0513    

DOI:10.1002/recl.19961150205

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractTwelve chiral ligands718were tested in the new kinetically controlled variation of zirconium alkoxide catalysed Meerwein‐Ponndorf‐Verley reduction of 2′‐chloroacetophenone (2) usingrac‐4as the reducing alcohol (Scheme 3). The tetraaryl‐1,3‐dioxolanes11(ca.30% enantiomeric excess,ee) and the triphenylethanediol14(62%ee, 99% yield) gave the best results. A relatively low dependence on the amount of the catalyst (aluminum alkoxide gave no asymmetric induction) and the ligand excess was observed compared with a very high dependence on incubation time of Zr(OtBu)4with the chiral ligand14and also on the reactio

ISSN:0165-0513    

DOI:10.1002/recl.19961150206

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

Abstract1‐Allenylpyrrole is lithiated at the α‐carbon atom of the allenyl group byn‐butyllithium in mixtures of diethyl‐ether/hexane or tetrahydrofuran/hexane. Whereas functionalization with trimethylchlorosilane, butyl iodide and dimethyl disulfide gives only allenic derivatives, addition of carbonyl compounds generally leads to mixtures of allenic and acetylenic derivatives. Upon heating its solutions in ether or tetrahydrofuran, Li‐allenylpyrrole is slowly transformed into the lithium derivative of 1‐(propyn

ISSN:0165-0513    

DOI:10.1002/recl.19961150207

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19961150208

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractDihydroazulenones5and6were prepared by photochemical isomerisation from their isomers7and8, respectively.5and6were found to be substantially in equilibrium with the norcaradiene forms, although isomers7and8exist as the cycloheptatriene forms.

ISSN:0165-0513    

DOI:10.1002/recl.19961150209

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractCycloaddition reaction of 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione(PTAD) to bicyclo[5.3.0]‐deca‐1(7),2,4‐trien‐10‐one (3) was reinvestigated. In various conditions, the reaction afforded solely 1:1 cycloadduct as reported. The structure of this adduct, previously thought to be a formal [6+2] adduct, was revised. This adduct is now thought to be a cycloheptatriene‐derived [4+2]adduct on the basis of extensive1

ISSN:0165-0513    

DOI:10.1002/recl.19961150210

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19961150212

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY