摘要:

Exchange of Carbonyl Group Sites in Tetracarbonyl(η‐(Z)‐cycloalkene)iron ComplexesviaNon‐BerryPseudorotationThe tetracarbonyliron complexes of cyclobutene, cyclopentene, 4,4‐dimethyl‐cyclopentene, 2,5‐dihydrofurane, cyclohexen, (Z)‐cyclohepten, ‐octene, ‐nonene, and ‐decene were prepared by thermal or photochemical reaction of the corresponding olefins with nonacarbonyldiiron and pentacarbonyliron, respectively. The low‐temperature behaviour of the mostly new complexes which can be stored over a longer period only below 250 K and which exhibit four C,O‐stretching frequencies in the IR. spectra(cf. Table 2), indicative for a trigonal bipyramidal structure with the olefin ligand in an equatorial position, was studied in CCl2F2by13C‐NMR. spectroscopy between 200 and 115 K. In this temperature range all complexed olefin ligands with the exception of (Z)‐cyclooctene (cf.[11]) show an averagedCs‐symmetry on the NMR. time scale. About 115 K the tetracarbonyliron group gives rise to three13C‐signals in a ratio of 1:1:2 for the complexes of (Z)‐cycloheptene, (Z)‐cyclodecene and 2,5‐dihydrofurane(Cf. Table 3). This is an agreement with the fixed equatorial position of the non‐rotating olefin ligands. The complexes of cyclooctene and cyclononene give only two13C‐signals in a ratio of 1:1 for the carbonyl groups. The temperature dependence of the signals indicates that in these cases the two axial carbonyl groups exhibit accidentally the same chemical shift. In all cases a complete line shape analysis of the13C‐signals of the carbonyl groups could only be accomplished by using two exchange constants (cf. Tables 4and5as well asFig. 2–5andFig. 8). The same is true for the cyclobutene complex, but only one exchange constant could be determined (at 120 K: two13C‐signals in a ratio of 1:3 with the beginning of a further coalescence). The cyclopentene and cyclohexene complexes showed only one13C‐signal even at 115 K. The observed temperature‐dependent line shapes of the13C‐signals can be interpreted in terms of a Non‐Berrypseudorotation mechanism involving a three site exchange with each of the two diastereotopic axial carbonyl groups and the two equatorial carbonyl groups (for activation parameters seeTable 4). The differences in the activation parameters can be explained on steric grounds by assuming a transition state(cf. Fig. 8)similar to theC3b‐structure of tetracarbonyliron which lies about 27 kJmol−1above itsC2v‐structure(cf.[30]) comparable with the ground state of our complexes with weak dπ(Fe),pπ(Olefin) back bonding. The transition state model implies that the reorganization process involving the axial carbonyl group

ISSN:0018-019X    

DOI:10.1002/hlca.19830660102

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

The [2.2.2]hericene (6), a bicyclo[2.2.2]octane bearing three exocyclics‐cis‐butadiene units has been prepared in eight steps from coumalic acid and maleic anhydride. The hexaene6adds successively three mol‐equiv. of strong dienophiles such as ethylenetetracarbonitrile (TCE) and dimethyl acetylenedicarboxylate (DMAD) giving the corresponding monoadducts17and20(k1), bis‐adducts18and21(k2) and tris‐adducts19and22(k3), respectively. The rate constant ratiok1/k2is small as in the case of the cycloadditions of 2,3,5,6‐tetramethylidene‐bicyclo [2.2.2]octane (3) giving the corresponding monoadducts23and27(k1) and bis‐adducts25and29(k2) with TCE and DMAD, respectively. Constrastingly, the rate constant ratiok2/k3is relatively large as the rate constant ratiok1/k2of theDiels‐Alderadditions for 5,6,7,8‐tetramethylidenebicyclo [2.2.2]oct‐2‐ene (4) giving the corresponding monoadducts24and28(k1) and bis‐adducts26and30(k2). The following second‐order rate constants (toluene, 25°) and activation parameters were obtained for the TCE additions:3+TCE→23:k1= 0.591±0.012 mol−1·l·s−1, ΔH≠=10.6±0.4 kcal/mol, and ΔS≠= −24.0±1.4 cal/mol·K (e.u.);23+TCE→25:k2=0.034±0.0010 mol−1·l·s−1, ΔH≠= 10.6±0.6 kcal/mol, and ΔS≠= −29.7±2.0 e.u.;4+TCE→26:k1= 0.172±0.035 mol−1·l·s−1, ΔH≠11.3±0.8 kcal/mol, and ΔS≠= −24.0±2.8 e.u.;24+TCE→26:k2= (6.1±0.2)·10−4mol−1·l·s−1, ΔH≠= 13.0±0.3 kcal/mol, and ΔS≠= −29.5±0.8 e.u.;6+TCE→17:k1= 0.136±0.002 mol−1·l·s−1, ΔH≠= 11.3±0.2 kcal/mol, and ΔS≠= −24.5±0.8 e.u.;17+TCE→18:k2= 0.0156±0.0003 mol−1·l·s−1, ΔH≠= 10.9±0.5 kcal/mol, and ΔS≠= −30.1 ± 1.5 e.u.;18+TCE→19:k3=(5±0.2) · 10−5mol−1mol−1·l·s−1, ΔH≠= 15±3 kcal/mol, and ΔS≠= −28 ± 8 e.u. The following rate constants were evaluated for the DMAD additions (CD2Cl2, 30°):6+DMAD→20:k1= (10±1)·10−4mol−1· l·s−1;20+DMAD→21:k2= (6.5±0.1) · 10−4mol−1·l·−1;21+DMAD→22:k3= (1.0±0.1) · 10−4mol−1·l·s−1.The reactions giving the barrelene derivatives19, 22, 26and30are slower than those leading to adducts that are not barrelenes. The former are estimated less exothermic than the latter. It is proposed that theDiels‐Alderreactivity of exocyclics‐cis‐butadienes grafted onto bicycle [2.2.1]heptanes and bicyclo [2.2.2]octanes that are modified by remote substitution of the bicyclic skeletons can be affected by changes inthe exothermicity of the cycloadditions, in agreement with the Dimroth andBell‐Evans‐Polanyiprinciple.Force‐field calculations (MMPI 1) of3, 4, 6and related exocyclics‐cis‐butadienes as a moiety of bicyclo [2.2.2]octane suggested single minimum energy hypersurfaces for these

ISSN:0018-019X    

DOI:10.1002/hlca.19830660103

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

(Phenacetin)4·2I4·2H2O is triclinic,a= 13.641 (7),b= 12.807 (6),c= 7.201 (3) Å, α = 99.8 (4), b̃ = 86.5 (4), γ = 104.0 (5)°,P1, Z = 1. The ordered crystal structure has been refined toRF= 0.050, using 4173 independent reflections measured on a four‐circle diffractometer with MoKa(graphite monochromator) radiation. The crystals are composed of alternating positively and negatively charged slices; each positive slice contains a double layer of stacks of hemi‐protonated phenacetin molecules which are H‐bonded through their carbonyl groups (d(O ‐ ‐ ‐ O) = 2.432 (4) Å) while each negative slice contains a single layer of I2−4‐ions linked in chains along [100] through H‐bonds to pairs of water molecules. The axes of the phenacetin stacks are parallel to the planes of the (I2−4·2H2O)‐layers. The I2−4‐ion is centro‐symmetric and can be approximately represented as I−‐ ‐ ‐ I–I‐ ‐ ‐ I−(d(I−‐ ‐ ‐ I) = 3.404 (1) Å; d(

ISSN:0018-019X    

DOI:10.1002/hlca.19830660104

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

The didehydrocorrinoid derivative of vitamin B12, ‘pyrocobester’1(hexamethylCoα, Cob̃‐dicyano‐7‐de (carboxymethyl)‐7,8‐didehydrocobyrinate), is oxygenated in the presence of visible light and molecular oxygen to give the previously unknown ‘5,6‐dioxosecopyrocobester’3(hexamethylCoα, Cob̃‐dicyano‐5,6‐dioxo‐7‐de(carboxymethyl)‐7,8‐didehydro‐5,6‐secocobyrinate) under regioselective cleavage of the macrocycle at the 5,6‐position. Efficiency and yield of this reaction involving ‘singlet oxygen’ depend on the so

ISSN:0018-019X    

DOI:10.1002/hlca.19830660105

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

The influence of steric compression on electronic structure in polycyclic olefinic alcohols and amines is studied by PE. spectroscopy.The unsubstituted alcohol2and amine7show PE.‐spectroscopic properties that can be reconciled by postulating a predominance of intramolecularly H‐bonded species in the gas phase.For the alkylated derivatives5and9, in which H‐bonding is precluded, distinct, but only moderate lone‐pair double‐bond interactions are

ISSN:0018-019X    

DOI:10.1002/hlca.19830660106

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

Formation of a Highly Explosive Valence Isomer of Indene from Dilithiopentalene and ChlorocarbeneThe principal product of the reaction of dilithiopentalene (3) with methyllithium and methylene chloride is shown by difference‐FT‐NMR, spectroscopy to be tetracyclo[4.3.0.03,5.04,6]nona‐1,7‐diene (8). This laterally bridged benzvalene derivative explodes violently at temperatures as low as −40° when concentrated. Controlled rearrangement in diluted solution gives indene (4). The key step in the formation of the tetracyclic C9H8‐compound8is suggested to be an intramolecular 1,4‐ca

ISSN:0018-019X    

DOI:10.1002/hlca.19830660107

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

Syntheses of Sulfonated Derivatives of 2‐FluoroanilineSynthesis of 4‐amino‐3‐fluorobenzenesulfonic acid (3) was achieved in two ways: reaction of 2‐fluoroaniline (1) with amidosulfonic acid and by first conventionally converting 4‐nitro‐3‐fluoroaniline (8) to 4‐nitro‐3‐fluorobenzenesulfonyl chloride (9) followed subsequently by hydrolysis to 3‐fluoro‐4‐nitrobenzenesulfonic acid (10) and reduction. Hydrogenolysis of3gave sulfanilic acid (7). Both, sulfonation of fluorobenzene (6) to 4‐fluorobenzenesulfonic acid (11) followed by nitration and sulfonation of 1‐fluoro‐2‐nitrobenzene (12) led to 4‐fluoro‐3‐nitrobenzenesulfonic acid (13). Reduction of13gave the isomeric 3‐amino‐4‐fluorobenzenesulfonic acid (4), which was also obtained both by sulfonation of1and by sulfonation ofo‐fluoroacetanilide (14) followed by hydrolysis. Selective hydrogenolyses of 2‐amino‐5‐bromo‐3‐fluorobenzenesulfonic acid (15), prepared by reaction of 4‐bromo‐2‐fluoroaniline (16) with amidosulfonic acid, and of 4‐amino‐2‐bromo‐5‐fluorobenzenesulfonic acid (20), obtained by sulfonation of 5‐bromo‐2‐fluoroaniline (19) yielded the isomers 2‐amino‐3‐fluorobenzenesulfonic acid (5) and3, respectively. The fourth isomer, 3‐amino‐2‐fluorobenzenesulfonic acid (2), was synthesized by sulfur dioxide treatment of the diazonium chloride derived from 2‐fluoro‐3‐nitroaniline (21) to 2‐fluoro‐3‐nitrobenzenesulfonyl chlo

ISSN:0018-019X    

DOI:10.1002/hlca.19830660108

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

Ph3ÅsBr is trapped in an X‐irradiated single crystal of Ph3As+CH3Br−. The g‐tensor, the75As and79Br magnetic hyperfine tensors and the79Br quadrupolar interaction tensor are obtained at room temperature. They show that the structure of this arsoranyl radical is intermediate between the trigonal bipyramidal and theC3v‐symmetry structure. By the detection of several additional radical species, especially at 77 K, some steps of the radiation mechanism are el

ISSN:0018-019X    

DOI:10.1002/hlca.19830660109

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

Syntheses of the Enantiomeric Aleuriaxanthins. Detection of a Predominant (Z)‐Aleuriaxanthin inAleuriaThe enantiomeric C10‐building blocks9((+)‐(2E, 6 R)‐6, 7‐dihydroxy‐3, 7‐di methyl‐2‐octen‐l‐yl acetate) andent‐9, and11((+)‐(2E, 6R)‐3, 7‐dimethyl‐2, 7‐octadien‐l, 6‐diyl diacetate) andent‐11, prepared from the optically active epoxy‐geraniols7andent‐7, respectively, have been used for the syntheses of (2′R)‐aleuriaxanthin (1) and (2′S)‐aleuriaxanthin (ent‐1).At room temperature aleuriaxanthin exhibits no significant CD. nor ORD. However, at −180° a very distinct CD. was observed, which in the UV. range showed a surprising resemblance to that of (3R, 3′R)‐zeaxanthin. By direct comparison of1with aleuriaxanthin isolated fromAleuria aurantia[2], the (2′R)‐chirality assigned to the latter byLiaaen‐Jensen et al.[5] is confirmed.HPLC. separation of the mixture of carotenoids fromAleuriashows the presence

ISSN:0018-019X    

DOI:10.1002/hlca.19830660110

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY

摘要:

On the Structure Elucidation of Niphimycin, Part I. Purification and Characterization of the Niphimycins Iα and Ib̃; Degradation by Nitric AcidFrom a sample of niphimycin the pure components, niphimycin Iα and Ib̃, were isolated by column chromatography and droplet counter‐current chromatography. They were characterized by UV., IR.,1H‐NMR. (300 MHz) and13C‐NMR. spectra. A vigorous degradation of niphimycin with nitric acid, followed by esterification with diazomethane, gave a complex mixture, from which many components could be isolated and identified. Several of the degradation products were synthesized, one of them (dimethyl 2,4‐dimethyladipate) in a stereospecific manner, establishing the configuration of two of the centers of chirality of niphimycin.Niphithricin was identified with copiamycin and yielded with nitric acid a degradation mixture very similar to that from niphimycin. The structures of the degradation products are in good agreement with a macrolide‐type structure of niphimycin and copiamycin.Further work for structure elucidation of niphimycin and copiamycin i

ISSN:0018-019X    

DOI:10.1002/hlca.19830660111

出版商:WILEY‐VCH Verlag GmbH    

年代:1983

数据来源: WILEY