摘要:

AbstractOn ultraviolet irradiation in toluene, cyclopent‐2‐en‐one (1a) and 3‐methylcyclopent‐2‐en‐one (1b) undergo dimerisation (→3a, b, 4b), whereas 3‐t‐butyl‐cyclopent‐2‐en‐one (1e) and the bicyclo [3.2.1]octenone2aonly react with the solvent (→5e–7e, 8–10). The 3‐ethyl‐(1c) and 3‐isopropyl‐cyclopent‐2‐en‐ones (1d) afford by dimerisation products3c, d, 4cand by reaction with the solvent5c, d, 6c, d, 7d. The β‐methoxy‐enones1fand2bare unreactive under comparable irradiation conditions. The head‐to‐head cyclobutane dimer3b(HH) by separate irradiation at<3400 Å in toluene, is reconverted to1b. By similar irradiation each of the head‐to‐tail dimers3b(anti‐ andsyn‐HT) and also the unsaturated dimer4bgive a new isomer of unknown structure besides small amounts of monomer1band relatively large amounts of insoluble material.The photoreactions of1b‐ecan be quenched by naphthalene.Stern‐Volmerplots for the quenching of the dimers of1b, 1c, and1d, and of3‐t‐butylcyclopentanone (5e) and the dihydro dimer7eare linear and within each experiment, the slopes satisfactorily coincide, whereas the slope for the α‐benzyl ketone6cis distinctly greater than that for the dimers3c. A similar differentiation, although less pronounced, is fou

ISSN:0018-019X    

DOI:10.1002/hlca.19710540602

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractThe tetrahydroxyadipic acids and one trihydroxyadipic acid have been methylated, using methyl iodide and silver oxide in the presence of dimethylformamide.In addition to Δ2‐di‐ or tri‐methoxyadipic esters and the products expected for a doubleE2 elimination,cis‐transα, α'‐dimethoxymuconic ester was frequently the principal product. The proposed theoretical interpretations involve as intermediates either a silver complex or a lactonic compound. A few preferential conformations, based on NMR. data,

ISSN:0018-019X    

DOI:10.1002/hlca.19710540603

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractProton NMR. spectra of purine, adenine, guanine and methylsubstituted guanines have been measured in CF3COOH, FSO3H and FSO3HSbF5SO2at 27° and low temperatures. These conditions permit to study multiple protonation of purines, using chemical shifts of CH, NH and OH protons. The spectra of mono‐, di‐ and tri‐cations are described and full

ISSN:0018-019X    

DOI:10.1002/hlca.19710540604

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractThe photoelectron spectrum of thiazyl fluoride has been recorded. An assignment of the first five bands has been attempted, using semi‐empirical calculation

ISSN:0018-019X    

DOI:10.1002/hlca.19710540605

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractDie Darstellung der drei optisch aktiven natürlichen Alkaloide Cryptostyline I, II und III ausCryptostylis fulva Schltr. und ihrer drei unnatürlichen Antipoden wird beschrieben. Es wird gezeigt, dass die drei natürlichen CryptostylineS‐Konfiguration besitzen. Die berichtete leichte Racemisierbarkeit der natürlichen Cryptostyline wird auf optische Unreinheit der ursprünglichen Präparate zurüc

ISSN:0018-019X    

DOI:10.1002/hlca.19710540606

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractThe reactions of benzalacetone withn‐BuMgBr and PhMgBr have been compared with the corresponding reactions with the diorganomagnesium complexes of ether and pyridine. The results obtained by using different mole ratios of reactants and orders of addition show that the conjugated addition reaction is enhanced if a monomeric diorganomagnesium reagent is available; this condition can be realized either by adding a diorganomagnesium complex to the ketone or by complexing the diorganomagnesium with pyridine. Probable reaction mechanisms for normal and conjugated addition reactions are suggeste

ISSN:0018-019X    

DOI:10.1002/hlca.19710540607

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractA possibility of correlating electronic and photoelectron spectra is discussed, usingtrans‐azomethane as an example. TheCoulomband exchange integrals required were obtained by three semi‐empirical SCF‐methods: MINDO/2, CNDO/2, and a modified CNDO method. The orbital energies were taken as minus the corresponding experimental ionization potentials. The sequence of the transition energies ΔE(ns→ π*) Δ E (na→ π*)<ΔE(π → π*) is found to be different from the ionization potential sequence IP (ns)

ISSN:0018-019X    

DOI:10.1002/hlca.19710540608

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractWhen heated with one equivalent of H2O, the 1,2: 5,6‐di‐O‐isopropylidene‐α‐D‐ribo‐ and ‐xylo‐hexofuranos‐3‐uloses loose one molecule of acetone and yield the 3, 6‐anhydro‐1, 2‐O‐isopropylidene‐α‐D‐ribo‐ and ‐xylo‐hexofuranos‐3‐ulose ketohydrols. The carbonyl group of the starting material seems to provide some kind of intramolecular electrophilic assistance to the hydrolysis of the 5, 6‐O‐isopropylidene group. When the oxygen of the carbonyl group is replaced by cyanomethylene, an analogous cyclisation takes place under base cata

ISSN:0018-019X    

DOI:10.1002/hlca.19710540609

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractSubstanceX, one of the three compounds obtained upon heating 5, 6‐endo‐epoxy‐hexamethyl‐bicyclo[2.2.0]hex‐2‐ene (11) and previously postulated byKlaus et al.[10] to be 5‐acetyl‐pentamethyl‐bicyclo[2.1.0]pentene (9), is now shown to be hexamethyl‐2‐oxabicyclo[3.2.0]‐hepta‐3, 6‐diene (10) by reinterpretation and supplementation of the spectral data and by ozonization of the dihydro derivative16, which yields 1‐acetoxy‐2‐acety‐1‐1, 2, 3, 4‐tetramethyl‐cyclo‐butane (17). It is concluded that theClaisenequilibrium in this system lies entirely on the side of the enol ether10; even drastic LiAIH4conditions cannot force a reversal (10→9). Tetracyanoethylene adds to the enol

ISSN:0018-019X    

DOI:10.1002/hlca.19710540610

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY

摘要:

AbstractThe pyrrolidide group is, in contrast to the carboxy‐ and ester groups, capable of inducing strong electron impact fragmentation at the b̃‐ and γ‐bonds in complicated alicyclic and aliphatic compounds. The fragments so formed allow certain conclusions concerning the structure in the neighbourhood of the functiona

ISSN:0018-019X    

DOI:10.1002/hlca.19710540611

出版商:WILEY‐VCH Verlag GmbH    

年代:1971

数据来源: WILEY