Herstellung neuer polycyclischer Verbindungen durch intramolekulare Diels-Alder-Reaktionen von Cyclohexa-2,4-dien-1-on-Abkömmlingen

Synthesis of new polycyclic compounds by means of intramolecular Diels-Alder reactions of cyclohexa-2,4-dien-1-one derivatives Thermal rearrangement of mesityl penta-2,4-dienyl ether ( 1 ), consisting of the isomers E (93%) and Z (7%), furnished, besides mesitol, the two mesityl penta-1,3-dienyl ethers 2 (24%) and 3 (3%), and the two tricyclic ketones 4 (4,5%) and 5 (12,5%) (Scheme 1). A probable mechanism for this formation of 2 involves a [1,5]-hydrogen shift in (Z)- 1 . Isomerisation of (E)- 1 to (Z)- 1 at 145° occurs via reversible sigmatropic [3,3]- and [5,5]-rearrangements of (E)- 1 to the cyclohexadienones 38 and 39 respectively (see Chapter A p. 1710, and Scheme 15). Formation of 3 from either (Z)- 1 or 2 is rationalized by a series of pericyclic reactions as outlined in Chapter A and Scheme 16. The tricyclic ketones 4 and 5 are undoubtedly formed by internal Diels-Alder reactions of the 6-pentadienyl-cyclohexa-2,4-dien-1-one 6 (Scheme 2). In fact, at 80° 6 is converted into 4 (5%) and 5 (35%). At 80° the cyclohexadienone derivative 7 furnished the corresponding tricyclic ketones 8 (15%) and 9 (44%) (Scheme 2). 5 and 9 contain a homotwistane skeleton. 8 and 9 are easily prepared by reaction of sodium 2,6-dimethylphenolate with 3-methyl-penta-2,4-dienyl bromide at ambient temperature, followed by heating, and finally separation by cristallization and chromatography. The cyclohexadienones 6 and 7 have mainly (E)-configuration. Here too (E) → (Z) isomerization is a prerequisite for the internal Diels-Alder reaction, and this partly takes place intramolecularly through reversible Claisen and Cope rearrangements (Scheme 17). On the other hand, experiments in the presence of 3,5-d₂-mesitol have shown (Table 1) that intermolecular reactions, involving radicals and/or ions, are also operating (see Chapter B , p. 1712). Two different modi (I and II) exist for intramolecular Diels-Alder reactions (Scheme 18). Whereas only modus I is observed in the cyclization of 5-alkenyl-cyclohexa-l,3-dienes, in that of (2)-cyclohexadienones 6 and 7 (Scheme 2) both modi are operating. Only in modus 11-type transitions is the butadienyl conjugation of the side chain retained, so that modus 11-type addition is preferred (Chapter C p. 1716). Analogously to the synthesis of the tricyclic ketones 4 , 5 , 8 and 9 , the tricyclic ketone 15 (Scheme 4) and the tetracyclic ketone 11 (Scheme 3) are prepared from mesitol, pentenyl bromide and cycloheptadienyl bromide, respectively. From the polycyclic ketones derivatives such as the alcohols 16 , 17 , 18 , 19 , 23 , 24 and 25 (Schemes 9 and 11), policyclic ethers 20 , 21 , 22 and 26 (Scheme 10), epoxides 30 , 32 (Scheme 13), diketones 31 , 33 (Scheme 13) and ether-alcohols 35 and 36 (Scheme 14) have been prepared. Most of these conversions show high stereoselectivity.     

Latex Fractionation by Sedimentation and Colloidal Crystallization: The Case of Poly(styrene-co-acrylamide)

Poly(styrene-co-acrylamide) (PS-AAM) latex was prepared, fractionated by sedimentation under gravity, and characterized by PCS, infrared spectra, secondary and backscattered electron imaging in the scanning electron microscope, and electron spectroscopy imaging in an analytical transmission electron microscope. Three latex fractions were obtained. The lower fraction was opalescent and its particles were the more uniform, concerning size, chemical composition, and topochemical features. This lower fraction was still further fractionated by zonal centrifugation in a density gradient, yielding two fractions with similar macrocrystal-forming abilities but different sizes and chemical compositions. These results confirm those previously obtained for the PS-HEMA latex. Copyright 2000 Academic Press.     

Designing new metal affinity peptides by random mutagenesis of a natural metal-binding site

The metal-binding site of a Helicobacter pylori ATPase 439 (heli(WT)-tag) was successfully used as a new fusion peptide for immobilized metal ion affinity chromatography (IMAC). It produced higher yields than the frequently used his6-tag. Due to stronger binding of the peptide to metal ions, harsher elution conditions were, however, necessary. This undesired side-effect was overcome by modifying the heli(WT)-tag by polymerase chain reaction-directed mutagenesis. The modified tags were screened by an automated high-throughput IMAC system, leading to a heliM14-tag peptide that could be eluted under conditions similar to those of the his6-tag but at the same time produced 20% higher yields of the desired protein.     

Oxydative Kupplung von Indolinen und 1,2,3,4-Tetrahydrochinolinen mit Kaliumpermanganat. 153. Mitteilung über Alkaloide

It is shown that treatment of indolines like 4a-methyl-1,2,3,4,4a,9a-hexahydrocarbazole ( 1 ) and even indoline-alkaloids like 5 or 6 (cf. scheme 1) with KMnO₄ in boiling acetone solution leads to the indolenines 10, 29 and 33 , respectively, and, in relatively high yields, to N,N′- or C,N-coupling products (cf. schemes 2 and 5). The results of the oxidation of 6- or 8-methoxy-indolines are shown in schemes 3 and 4, respectively. Analogous ‘dimeric’ dehydrogenation products are observed when tetrahydroquinolines ( 8 and 9 , resp.) are treated with KMnO₄ (cf. schemes 7 and 8, resp.). The formation of the bis-compounds is almost certainly due to the coupling of two intermediate indolenyl or tetrahydroquinolyl radicals. The cleavage of the hydrazine derivatives 11 or 17 (scheme 9) also leads to ‘dimeric’ C,N-coupling products. By heating the hydrazine derivative 17 with aqueous HCl, a complete cleavage into indoline 2 and the indolenines 16 and 20 is observed. The reaction is rationalized in scheme 10. So far no naturally occurring alkaloids related to the above mentioned C,N-coupling products have been found.     

Zur Struktur und Reaktivität von stannylierten Propylaminen und -sulfiden. Kristall- und Molekülstruktur von Bis(3-dimethylchlorostannylpropyl)sulfid S(CH2CH2CH2SnMe2Cl)2

Structure and Reactivity of Stannylated Propyl Amines and Propyl Sulfides. Crystal and Molecular Structure of Bis(3-chlorodimethylstannylpropyl)sulfide S(CH₂CH₂CH₂SnMe₂Cl)₂ The synthesis and reactivity of stannylated propyl amines and propyl sulfides, respectively, E(CH₂CH₂CH₂SnMe₃)₂ ( 1 , E ? NMe; 2 E ? S) and N(CH₂CH₂CH₂SnMe₃)₃ 3 are reported. 1 and 3 react with dimethyl dichlorostannane under thermal cyclisation to 1,5-dimethyl-5-chloro-1aza-5-stannabicyclo[3.3.0^1,5]octane Me(Cl)Sn(CH₂CH₂CH₂)₂NMe 4 and 5-chloro-1-aza-5-stannatricyclo[3.3.3.0^1,5]-undecane ClSn(CH₂CH₂CH₂)₃N 5 , respectively. The reaction of 2 with dimethyl dichlorostannane leads to the formation of bis(3-chloro-dimethylstannylpropyl)sulfide S(CH₂CH₂CH₂SnMe₂Cl)₂ 6 , whereas the treatment of 2 with tin tetrachloride yields the bis(3-di-chloro-methylstannylpropyl)sulfide S(CH₂CH₂CH₂SnMeCl₂)₂ 7 . The ¹H, ¹³C, and ¹¹⁹Sn NMR data are discussed. 6 crystallizes in the ortho-rhombic space group Pna2₁ with the unit cell parameters a = 2275.0(1), b = 733.6(2), c = 1062.0(4) pm, V = 1.77273 nm³, Z = 4. The structure was refined to a final R value of 0.041. Both tin atoms adopt distorted trigonal bipyramidal configurations as a result of intramolecular interactions with the bridging sulphur. The sulphur and the chlorine atoms occupy the apical positions. The Sn? S distances amount to 309.7(4) and 311.8(4) pm.     

Isomeric [RuCl2(dmso)2(indazole)2] complexes: ruthenium(II)-mediated coupling reaction of acetonitrile with 1H-indazole

Reaction of the antitumor complex trans-[Ru(III)Cl4(Hind)2]- (Hind = indazole) with an excess of dimethyl sulfoxide (dmso) in acetone afforded the complex trans,trans,trans-[Ru(II)Cl2(dmso)2(Hind)2] (1). Two other isomeric compounds trans,cis,cis-[Ru(II)Cl2(dmso)2(Hind)2] (2) and cis,cis,cis-[Ru(II)Cl2(dmso)2(Hind)2] (3) have been obtained on refluxing cis-[Ru(II)Cl(2)(dmso)(4)] with 2 equiv. of indazole in ethanol and methanol, respectively. Isomers 1 and 2 react with acetonitrile yielding the complexes trans-[Ru(II)Cl2(dmso)(Hind){HN=C(Me)ind}].CH3CN (4.CH3CN) and trans,cis-[Ru(II)Cl2(dmso)2{HN=C(Me)ind}].H2O (5.H2O), respectively, containing a cyclic amidine ligand resulting from insertion of the acetonitrile C triple bond N group in the N1-H bond of the N2-coordinated indazole ligand in the nomenclature used for 1H-indazole. These are the first examples of the metal-assisted iminoacylation of indazole. The products isolated have been characterized by elemental analysis, IR spectroscopy, UV-vis spectroscopy, electrospray mass-spectrometry, thermogravimetry, differential scanning calorimetry, 1H NMR spectroscopy, and solid-state 13C CP MAS NMR spectroscopy. The isomeric structures of 1-3 and the presence of a chelating amidine ligand in 4 and 5 have been confirmed by X-ray crystallography. The electrochemical behavior of 1-5 and the formation of 5 have been studied by cyclic voltammetry.     

Photochemie von tricyclischen β, γ-γ′, δ′-ungesättigten Ketonen. 50. Mitteilung über Photoreaktionen

Photochemistry of tricyclic β, γ-γ′, δ′-unsaturated ketones The easily available tricyclic ketone 1 (cf. Scheme 1) with a homotwistane skeleton yielded upon direct irradiation the cyclobutanone derivative 3 by a 1,3-acyl shift. Further irradiation converted 3 into the tricyclic hydrocarbon 4 . However, acetone sensitized irradiation of 1 gave the tetracyclic ketone 5 by an oxa-di-π-methane rearrangement. Again with acetone as a sensitizer the ketone 5 was quantitatively converted to the pentacyclic ketone 6 . The conversion 5 → 6 represents a novel photochemical 1,4-acyl shift. The possible mechanisms are discussed (see Scheme 7). The tricyclic ketone 2 underwent similar types of photoreactions as 1 (Scheme 2). Unlike 5 the tetracyclic ketone 9 did not undergo a photochemical 1,4-acyl shift. The epoxides 10 and 14 derived from the ketones 1 and 2 , respectively, underwent a 1,3-acyl shift upon irradiation followed by decarbonylation, and the oxa-di-π-methane rearrangement (Schemes 3 and 4). The diketone 18 derived from 1 behaved in the same way (Scheme 5). The tetracyclic diketone 21 cyclized very easily to the internal aldol product 22 under the influence of traces of base (Scheme 5). Upon irradiation the γ, δ-unsaturated ketone 24 underwent only the Norrish type I cleavage to yield the aldehyde 25 (Scheme 6).     

Die Wasserstoffbrückenbildung als primärer Elementarvorgang bei der Ionisation schwacher Säuren und bei Säure-Basen-Katalysen in wäßriger Lösung

The mechanism of the ionisation of weak acids was elucidated according to the interpretation of the acid—base-catalysis of the mutarotation of α-glucose by the author. The primary elementary reaction of the ionisation of weak acids is the exothermic formation of the hydrogen bridge of the acid with the polar solvent. The secondary reaction is the endothermic total transfer of the proton to the solvent. The thermodynamic values of both elementary reactions were determined for the ionisation of different weak acids in aqueous solution and in this way a contribution was made to the thermodynamics of intermediate reactions which was propagated by the autorh. The formation of hydrogen bridge at the acid—base-catalysis of the mutarotation of α-glucose is discussed from the point of view of the mechanism of ionisation of weak acids. Furthermore the limits of the validity of theBrönsted equation for the acid—base-catalysis of the mutarotation of α-glucose were demonstrated.     

Axially Dissymmetric Bis(triaryl)phosphines in the Biphenyl series: Synthesis of (6,6′-dimethylbiphenyl-2,2′-diyl)bis(diphenylphosphine) (‘BIPHEMP’) and analogues,and their use in Rh(I)-catalyzed asymmetric isomerizations of N,N-diethylnerylamine

The axially dissymmetric diphosphines (?)-(R)- and (+)-(S)-(6-6′-dimethylbiphenyl-2,2′-diyl)bis(diphenyl-phosphine) ((?)-(R)- 10 and (+)-(S)- 10 ; ‘BIPHEMP’) have been synthesized, starting from (R)- and (S)-6,6′-dimethylbiphenyl-2,2′-diamine ((R)- and(S)- 16 ), respectively, via Sandmeyer reaction, liathiation, and phosphinylation. Moreover, racemic 4,4′- dimethyl- and 4,4′-bis(dimethylamino)-substituted analogues 11 and 12 respectively, and the 6,6′-bridged analogues 1,11-bis(diphenylphosphino)-5,7-dihydrodibenz[c,e]oxepin (13) were synthesized and resolved into optically pure (R)- and(S)-enantiomers via complexation with di-μ-chlorob is {(R)-2-[1-(dimethylamino)ethyl]pheny-C? N}dipalladium(II) ((R)- 18 ). The molecular structures of the diphosphines (S)- 10 and (R)- 13 and of two derived cationic Rh(I) complexes,[Rh((S)- 10 )(nbd)]BF₄ and [Rh((R)- 13 )(nbd)]BF 4 were determined by x-ray analyses. Absolute configurations were established for (+)-(S)- 10 by X-ray analyses of both the free diphosphine and of the derived Rh(I) complex, and for (?)-(R)- 13 by X-ray analysis of the derived Rh(I) complex. Configurational assignments for the substituted BIPHEMP analogues 11 12 were achieved by means of ¹H-NMR comparisons. The BIPHEMP ligand 10 and analogues 11 , 12 and 13 are the first examples of optically active bis(triaylphosphines) containing the axially dissymmetric biphenyl moiety. All these new diphosphines proved to be excellent asymmetry-inducing ligands in Rh(I)-catalyzed isomerizations of N,N-diethylnerylamine affording citronellat enamine of 98-99% ee.