摘要:

Abstract3‐Hydroxy‐3‐[(2‐ and 4‐pyridyl)methyl]‐1H‐indol‐2‐ones (1, 12) have been reduced with NaBH4/MeOH/t‐BuOH. After acidic treatment, 2‐ and 3‐substituted indoles (2, 11and13, 14, respectively) were obtained. The intermediates3and4of the rearrangement were isolated and the effect of the pyridylmethyl groups on the rearrangement ha

ISSN:0165-0513    

DOI:10.1002/recl.19911101102

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe reductive cleavage of mixedortho‐ andpara‐functionalized triarylphosphines with Na/NH3and Li/THF depends strongly on the nature and positions of the substituents. Reduction occurs readily with phosphines PhAr2P(4, 6and9) and Ph2ArP19when the corresponding phosphine Ar3P is not reduced. Cleavage ofpara‐substituted compounds7and9leads to mixtures of secondary phosphines. By contrast, cleavage of mixedortho‐substituted triphenylphosphines is very selective. The functionalized phenyl group is split off in high yield when it carries CH3, (CH3)2N and CH3O substituents (2, 3, 5, 6, 8, 10, 11, 13, 14, 17, 19, 24, 25). Reaction of4is not selective due to loss of methoxy groups. By contrast, the phenyl group is split off when the mixed phosphine contains phenoxide groups (1, 15, 16). The reactions of bis‐ and tris(diphenylphosphino)benzenes with Li/THF lead predominantly to cleavage of the diphenylphosphino group from the respective substrates.In a number of cases, the product of a Birch reduction with an isolated diene system is formed in NH3(1, 9, 12, 21, 23) via a phosphino‐stabilized cyclohexadienyl anion. This reduction does not occur in the aprotic solvent THF. Base‐catalyzed isomerization leads to a conjugated double‐bond system with a vinylphosphine moiety.We also report interesting largeaJ(PP) couplings in 1,3‐diphosphinobenzenes and complicated13C resonances ofpara‐sub

ISSN:0165-0513    

DOI:10.1002/recl.19911101103

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractAcid‐catalysed reaction of L‐arabinose with 2‐chloroethanol, 2‐bromoethanol or 2‐iodoethanol at 50‐60 °C, afforded the highly crystalline 2‐haloethyl β‐L‐arabinopyranosides in 20%, 86% and 23% yields respectively, which each crystallised out directly from the reaction mixtures. FollowingO‐acetylation of 2‐bromoethyl β‐L‐arabinopyranoside, the bromo substituent underwent substitution by various nucleophilic anions (N3−, NCS−, AcS−, BzO−) to give the appropriate acetylated functionalised glycosides.O,S‐Deacetylation of 2‐(acetylthio)ethyl 2,3,4‐tri‐O‐acetyl‐β‐L‐arabinoside afforded 2‐mercaptoethyl β‐L‐arabinopyranoside, but deblocking of the 2‐thiocyanatoethyl 2,3,4‐tri‐O‐acetyl‐P‐L‐arabinoside in the same way afforded the thiol as a minor product, with the derived disulphide and methylthio derivatives as the major products. The origin of these compounds is discussed. Reaction of the 2‐bromoethyl arabinoside with base afforded the as‐fused bicycle 1,2‐O‐ethylene‐β‐L‐arabinopyranose in high yield. Acetonation and subsequent oxidation of the 2‐azidoethyl arabinoside gave the 2‐ketone, reductive amination of which led to thetrans‐fused bicycle 2‐amino‐2‐deoxy‐1,2‐O, N‐ethylene‐β‐L‐ribose. Chlorination of 2‐chloroethyl β‐L‐arabinopyranoside with triphenylphosphine/carbon‐tetrachloride, followed by treatment with base afforded 3,4‐anhydro‐1,2‐O‐ethylene‐β‐L‐arab

ISSN:0165-0513    

DOI:10.1002/recl.19911101104

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe syntheses and spectroscopic properties of the all‐Eisomers of 11′,12′‐dihydrospheroidene (2), 3,4,11′,12′‐tetrahydrospheroidene (3), 3,4‐dihydrospheroidene (4), 3,4,5,6‐tetrahydrospheroidene (5), 3,4,7,8‐tetrahydrospheroidene (6) and 15,15′‐didehydrospheroidene (7) are described. Spheroidenes2‐6have the same overall shape as native spheroidene (1), which is the carotenoid bound in the photosynthetic reaction centre ofRhodobacter sphaeroides2.4.1, but they have instead polyene chromophores of nine (4), eight (2, 5) or seven (3, 6) conjugated double bonds. In7, the central double bond is substituted by a triple bond. The observed λmaxvalues of2‐6are generally in good agreement with those calculated via the Fieser‐Kuhn rules. In the mass spectra of2‐6, fragments due to bis‐allylic fragmentation occur, whereas1and7do not show this type of fragmentation. A detailed analysis of the1H‐ and13C‐NMR spectra of1

ISSN:0165-0513    

DOI:10.1002/recl.19911101105

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe complete assignment of the1H‐NMR spectrum of the fully saturated tetracyclic sesquiterpene hydrocarbon longicyclene is presented. The assignment was achieved using phase‐sensitive double‐quantum filtered COSY at 600 MHz, heteronuclear correlation spectroscopy and COLOC spectroscopy. Accurate vicinal1H‐1H coupling constants involving the seven‐membered ring protons were obtained using extensive simulation of the ID spectrum.Molecular mechanics calculations indicate that the title compound may adopt two conformations which differ mainly in the geometry of the seven‐membered ring. These geometries are best described as twist‐chair‐like conformations denoted TC11 and TC8, respectively. The energy of the TC11 conformer is predicted to be slightly lower (4.6 kJ/mol) than the energy of the TC8 conformer. The vicinal1H‐1H coupling constants of these two conformers were predicted from a generalized Karplus equation. The predicted coupling constants agree well with the experimental coupling constants if it is assumed that, in solution, longicyclene is engaged in a conformational equilibrium between TC11 (8

ISSN:0165-0513    

DOI:10.1002/recl.19911101106

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractPyrolysis of coumaran, 2,3‐dihydrobenzofuran,(Ia) atca. 700°C leads to the isomerico‐vinylphenolIlaand some benzofuranIIIa. The 2,3‐dimethyl derivativeIb‘directly’ givesIIIain a relatively easy double homolytic de‐methylation

ISSN:0165-0513    

DOI:10.1002/recl.19911101107

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

摘要:

AbstractThe first arylpalladium(IV) complexes, [PdXMePhR(bpy)] (bpy = 2,2′‐bipyridyl), have been isolated upon oxidative addition of methyl iodide or benzyl bromide to [PdMePh(bpy)]. These dialkyl(aryl)palladium(IV) complexes undergo reductive elimination in solution atca. 0 °C: [PdBrMePh(CH2Ph)(bpy)] decomposes quantitatively into [PdBr(CH2Ph)(bpy)] and toluene whereas [PdIMe2Ph(bpy)] gives ethane and toluene in 4: 1 ratio together with the corresponding complexes [PdIR(bpy)](R = Me or Ph). The reaction of methyl iodide with [PdMePh(tmeda)] at 0 °C yields ethane and [PdIPh(tmeda)]without detection of a palladium(IV) intermediate. No reaction of [PdMePh(tmeda)] with benzyl bromide was observed. The first demonstration that organic groups can be transferred from palladium(IV) to palladium(II) is reported. The molecular structure of [PdMePh(bpy)]in the solid state has been deter

ISSN:0165-0513    

DOI:10.1002/recl.19911101108

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19911101109

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19911101101

出版商:WILEY‐VCH Verlag    

年代:1991

数据来源: WILEY