摘要:

AbstractThe1H‐NMR spectra of 2‐(nitromethylidene)pyrrolidine (7), 1‐methyl‐2‐(nitromethylidene)imidazolidind (10) and 3‐(nitromethylidene)tetrahydrothiazine (11) in CDCl3and (CD3)2SO indicate that these compounds have the intramolecularly H‐bonded structures (Z)‐7, (E)‐10and (Z)‐11while theN‐methyl derivative8of7is (E)‐configurated in both solvents. 1‐Benzylamino‐1‐(methyltio)‐2‐nitroehtylene (13), an acylic model, has the H‐bonded configuration (E)‐13in CDCl3and in (CD3)2SO. 2‐(Nitromethylidene)thiazolidine (3) has the (E)‐configuration in CDCl3but exists in (CD3)2SO as a mixture of (Z)‐ and (E)‐isomers with the former predominating. Both species are detected to varying proportions in a mixture of the two solvents.15N‐NMR spectroscopy of3ruled out unambiguously the nitronic acid structure6and the nitromethyleimine structure5. TheN‐methyl derivative4of3is (Z)‐configurated in (CD3)2SO. Comparison of the olefinic proton shifts of (Z)‐3and (Z)‐4with those of analogues and also of 1,1‐bis(methylti)‐2‐nitroethylene (12) shows decreased conjugation of the lone pair of electrons of the ring N‐atom in (Z)‐3and (Z)‐4. This is also supported by13C‐NMR studies. Plausible explanations for the phenomenon are offered by postulating that the ring N‐atoms are pyramidal in (Z)‐3and (Z)‐4and planar in other cases or, alternatively, that the conjugated nitroenamine system gets twisted due to steric interaction between the NO2‐group and the ring S‐atom. Single‐crystal X‐ray studies of3and8show that the former exists in the (Z)‐configuration and the latter in (E)‐configuration;

ISSN:0018-019X    

DOI:10.1002/hlca.19840670702

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractEquivalent bond orbital (EBO) calculations by a procedure based on recalibrated, localized bond orbitals derived from anab initiomodel, suggest that the two frontier ‘ribbon’ orbitals φHOMO, φHOMO‐1of polycyclic hydrocarbons consisting of all‐trans‐connected six‐membered rings are well separated in energy from the remaining manifold of σ‐orbitals. Assuming the validity ofKoopmans' theorem, a PE‐spectroscopic investigation of perhydroanthracenes, 2‐methylperhydrophenalene and perhydroperylene have shown that this is indeed the case. According to the theoretical treatment these ribbon orbitals are evenly delocalized over the whole of the molecular frame and they conserve the characteristic phase relationship postulated byHoffmann et al.[16] for cyclohexane moieties. Their behaviour under the successive introduction of centres of unsaturation,i.e., of doubl

ISSN:0018-019X    

DOI:10.1002/hlca.19840670703

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractA PE‐spectroscopic study ofexo‐ andendo‐2‐norbornyl iodides suggests that the relative ability of the 2‐norbornyl group to stabilize an electron deficiency on a substituent X (e.g. I) inexo‐ orendo‐position depends on the location of the positive charge. There isnodifference if the positive hole is strongly localizedonon the substituent X (e.g.the 5p−1state of the title compounds). On the other hand, our results indicate that teh positive hole semi‐localizedinanexo‐CX bond is better stabilized by the 2‐norbornyl group than a semi‐localized, positiv

ISSN:0018-019X    

DOI:10.1002/hlca.19840670704

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractThe electrochemical synthesis of muscalure, (Z)‐9‐tricosene(1), has been carried out by coelectrolysis of erucic acid (2) and propionic acid (3) in an undivided cell in methanol. To optimize the yield of the cross coupled product1, the reaction has been studied in detail by varing different parameters,viz., electrode material, current density, molar ratio of2to3, degree of partial neutralization and quantity of water in metha

ISSN:0018-019X    

DOI:10.1002/hlca.19840670705

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

Abstract(±)‐2‐Pupukenone (4) has been synthesized, the key step being the intramolcularDiels‐Alderreaction of the intermediate13to14(42%) and15(14%). The bromodiene12has been obtained from the reaction of α‐isopropylidene‐γ‐lactone (Scheme 2)12with sodium phenylselenide and subsequent esterification to9, oxidation and thermal elimination of which furnished10. Reduction of10with diisobutylaluminimum hydride and treatment of the resulting alcohol11with PBr3led to the required bromodiene12. Finally, hydrogenation of the14on Pt(C) in CH3OH gave a 4:1 mixture of 2‐pupukeanone (4) and epi

ISSN:0018-019X    

DOI:10.1002/hlca.19840670706

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractThe deformation density and potential have been determined in molecular crystals of tricyclo[4.4.1.01,6]ndeca‐2,4,7,9‐tetraene‐11,11‐dicarbonitrile at 150 K from X‐ray diffraction measurements. A significant degformation density peak is found near the mid‐poind of the the transannular bond. The four short bonds in the annuelene ring acquire slightly more residual density compared to the other bonds, confirming the bisnorcaradienic character of the molecule. Similar trends are noted in the deformation electrostatic pot

ISSN:0018-019X    

DOI:10.1002/hlca.19840670707

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

Syntheses of Macrocyclic Lactones by Ring Enlargement Reaction Reaction. Preparation of (±)‐Phoracantholide I, (±)‐Dihydrorecifeiolide and (±)‐15‐HexadecanolideA general procedure for the synthesis of macrocyclic lactones is described. TheMichaeladducts of 2‐nitrocycloalkanones and acrylaldehyde were regiospecifically methylated with CH3Ti[OCH(CH3)2]3or (CH3)2Ti[OCH(CH3)2]2at the aldehyde carbonyl group. Treatment of the so‐formed alkohols with tetrabutylammonium fluoride gave the lactones enlarged by four ring members. This method was used to synthesize the 10‐membered (±)‐phoracantolide I (11), the 12‐membered (±)‐dihydrorecifeiolide (17), and (±)‐15‐hexadecanolide (24) in 52%,

ISSN:0018-019X    

DOI:10.1002/hlca.19840670708

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

γ‐Nitro‐γ‐butyrolactoneBy oxidation of 3‐(1‐nitro‐2‐oxocyclohexyl)propanal (1) with KMnO4, besides 3‐(1′‐nitro‐2′‐oxocyclohexyl)pripionic acid (2), the complete hydrolysis product 4‐oxononanedioic acid (4) and the oxidized semi‐hydrolysis product 5‐(2‐nitro‐5‐oxotetrahydro‐2‐furyl)pentanoic acid (3) were formed. The crystalline3decomposes at r.t. forming4and nitrous gases; its struc

ISSN:0018-019X    

DOI:10.1002/hlca.19840670709

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractA new coumarin diester has been isolated fromPolygala paniculataL. (Polygalaceae) by a combination of flash chromatography on silica gel and preparative reversed‐phase chromatography. Its structure has been determined as 3′‐O‐acetyl‐4′‐O‐benzoylkhellactone (=9‐acetoxy‐9,10‐dihydro‐8,8‐dimethyl‐2‐oxo‐2H,8H‐benzo[1,2‐b:3,4‐b′]dipyranh‐10‐yl benzoate) by spectroscopic methods (UV, IR,

ISSN:0018-019X    

DOI:10.1002/hlca.19840670710

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY

摘要:

AbstractThe Syntheses and the photolyses of the acylsilane1and the corresponding methyl ketone2are described. On n,π*‐excitation, the silyl ketone1as well as the methyl ketone2undergo aNorrishtype II reaction involving γ‐H‐abstraction and fragmentation to the diene12, and acetone (20) or the acylsilane26, respectively. The methyl ketone2, but not the acylsilane1, isomerizes to cyclobutanols (21A‐D). Additionally, compound1shows photochemical behavior typical of acylsilanes undergoing rearrangement to the siloxycarbene intermediatec. Insertion ofcinto the OH‐ond of the enol28leads to compound13. Initial trapping of the siloxycarbenecby H2O, however, gives rise to the formation of compounds16–18. As minor photolysis products of1, compounds14and (Z)‐15were formed; however, on vapor phase thermolysis (520°) of1, compounds14and (E/Z)‐15were obtained in 92% combined yield. To a small extent the acylsilane1also undergoesNorrishtype I cleavage l

ISSN:0018-019X    

DOI:10.1002/hlca.19840670711

出版商:WILEY‐VCH Verlag GmbH    

年代:1984

数据来源: WILEY