Synthese von ‘Push-Pull’-Diacetylenen

Synthesis of ‘Push-Pull’ Diacetylenes The first synthesis of push-pull diacetylenes of type 1 is described. Reaction of perchlorobutenyne ( 8 ) with two equivalents of dialkylamine, followed by dechlorination using two equivalents of butyllithium gives lithio-dialkylamino-diynes 7 . Final acylation of these intermediates leads to push-pull diacetylenes 1b–1e in good yields. The method allows the introduction of both push and pull substituents in a simple one-pot-procedure. In addition, 1a is prepared by hydroxymethylation of lithio-morpholino-diyne 7c , followed by oxidation with manganese dioxide in acetone.     

Versuche zur Synthese von ‘Push-Pull’-Diacetylenen

Attempted Synthesis of Push-Pull Diacetylenes Two alternative synthesis of push-pull diacetylenes of type 1 (5-amino-2,4-alkadiynals) are investigated. A bromination-dehydrobromination sequence starting with 5-dimethylamino-2,4-pentadienal ( 2 ) as well as the application of the well-known Cadiot-Chodkiewicz coupling reaction give new intermediates 3–5 , and 7 and 8 , respectively, but fail to give the target molecules 1 .     

Synthese von ‘Push-Pull’-Oligoacetylenen

Synthesis of ‘Push-Pull’-OligoAcetylenes ‘Push-pull’ triacetylenes 11a , b , c , as well as ‘push-pull’ tetraacetylene 13b have been prepared by reaction of the corresponding trichloroene(oligoinyl)amines 9 and 10 with 2 mol-equiv. of BuLi followed by acylation. The sequences (Schemes 3 and 4) are very simple and straightforward, they could in principle be applied to the synthesis of ‘push-pull’ pentaAcetylenes 15 and hexaacetylenes 17 (Scheme 5). Main limitations are the moderate yields as well as the low thermal stability of push-pull oligoacetylenes.     

Synthese von ‘Push-Pull’- Eninen

Synthesis of ‘Push-Pull’ Enynes ‘Push-pull’ enynes 1a–1f are easily available by Pd catalyzed coupling of stannyl-ynamines 15 and silylynamines 16 with β-iodo-enones 8 (Schemes 7 and 8).     

Der ‘Push-Pull’-Effekt von ‘Push-Pull’-Oligoacetylenen. Eine 13C-NMR-Untersuchung

The ‘Push-Poll’ Effect of ‘Push-Pull’ Oligoacetylenes. A ¹³C-NMR Investigation According to ¹³C-chemicaI shifts of ‘push-pull’ oligoacetylenes 1 – 4 , the ‘push-pull’ effect (i.e. π delocalization induced by ‘push-pull’ substituents) rapidly decays in this series. To correct for other than π -charge-density effects, Δδ values of symmetrically placed C-atoms of the oligoacetylene chain are discussed. Stereoelectronic resteffects (SER) of the substituents on terminal C-atoms of PP-ketones 1a – 3a and PP -esters 1b – 4b are estimated from the residual Δδ of the asymptotes of Fig. 3. Fig. 4 convincingly shows that Δδ values are dramatically decreasing with increasing number n of acetylene units between the push and pull substituents. Assignment problems of ‘push-pull’ triacetylenes 3 have been solved by ¹³C labelling of the CO group of 3a .     

Synthese von ‘D-Isothreonin’ und ‘L-Alloisothreonin’ aus L-Alanin

Synthesis of ‘D -Isothreonine’ and ‘L -Alloisothreonine’ Starting from L -Alanine Starting from L -alanine, ‘D -isothreonine’ ( = (2R, 3S)-3-amino-2-hydroxybutanoic acid) and ‘L -alloisothreonine’ ( = (2S, 3S)-3-amino-2-hydroxybutanoic acid) were synthesized.     

Synthese von enantiomerenreinen ‘Grasshopper’-Ketonen und verwandten Verbindungen

Synthesis of Optically Pure Grasshopper Ketone and of Its Diastereoisomers and Related Compounds Starting from our previously described synthon 1 , the synthesis of four enantiomerically pure grasshopper ketons (diastereoisomeric 4-(2′,4′-dihydroxy-2′,6′,6′-trimethylcyclohexylidene)but-3-en-2-ons) and of their oxo derivatives was performed. Spectral and chiroptical data are presented.     

Synthese und Struktur von AlTaO4

Synthesis and Structure of AlTaO₄ Single crystals of AlTaO₄ were prepared between 1310–1360°C and investigated by X-ray single crystal methods. It crystallizes with tetragonal symmetry (a = 460.6₅; c = 298.5 pm; space group D–P4₂/mnm). AlTaO₄ has got a statistical metal distribution with rutil structure. It shows metastable character in respect to lower temperatures.     

Bisaminophosphane – Synthese,Struktur und Reaktivität

Bisaminophosphanes – Synthesis, Structure, and Reactivity Different pathways for the synthesis of bis(alkylamino)phosphanes RP(N(H)R′)₂ are described. t‐BuP(N(H)‐ Dipp)₂ (Dipp = 2,6‐i‐Pr₂–C₆H₃) was structurally characterized by single crystal X‐ray diffraction. The reactivity of the compounds was examplarily investigated using t‐BuP(N(H)t‐Bu)₂. Its reaction with Me₃Al and R₂AlH (R = Me, Et, i‐Bu) in 1 : 1 and 1 : 2 stoichiometrie yield monosubstituted compounds of the type t‐BuP(N(H)t‐Bu)(N(AlR₂)t‐Bu).     

Festkörper-Polymerisation eines ‘Push-Pull’-Diacetylens

Solid-State Polymerisation of a ‘Push-Pull’-Diacetylene Solid-state polymerisation of ‘push-pull’-diacetylene 5-(diphenylamino)-1-phenylpenta-2,4-diyn-1-one ( 1d ), initiated by heating of crystals of 1d at 90°, gives ‘push-pull’ poly-diacetylene 2d . X-Ray results and spectroscopic data of monomer 1d as well as of polymer 2d are discussed.     

13C-NMR-Spektren von Cyclopropenen und Benzocyclopropenen

The substituent parameters of methyl-, halogen-, methoxycarbonyl- and phenyl-substituted cyclopropenes as well as of cyclopropenone and diphenylcyclopropenone are determined from the ¹³C chemical shifts. The influence of the carbonyl group on the chemical shifts and charge densities is studied in the cyclopropenones. The interaction between the cyclopropene nucleus and the annulated benzene ring in benzocyclopropenes is evaluated with the aid of the ¹³C NMR spectra of di- and tetraphenyl-substituted benzocyclopropene derivatives and of dimethyl 1H-cyclopropa[a]naphthalene-1,1-dicarboxylate. The J values are shown to be better indicators of structural changes than the δ values. α-Effects of substituents give a good correlation with Hammett σ₁-values.