A new approach for the synthesis of fused pyrroles. The synthesis of acyl substituted pyrrolo[1,2-x]azines

N-Acetonyl- and N-phenacyl quaternary salts of α-methyl substituted heterocycles 16, 17, 21, 23 and 26 were converted with DMFDMA into the corresponding 3-acylpyrrolo[1,2-a]pyridine 18 , 7-benzoylpyrrolo-[1,2-c]pyrimidine 22 , and 6-benzoylpyrrolo[1,2-a]pyrazine derivatives 24 and 27 . A concurrent reaction produced methyl and phenyl substituted pyrrolo[1,2-x]azines 19, 20, 25 and 28 .     

Negatively charged hyperbranched polyether-based polyelectrolytes

The preparation of carboxylated hyperbranched polyglycerols of narrow polydispersity was achieved by modification (78–90%) of the hydroxyl end groups via Michael addition of acrylonitrile, followed by hydrolysis. High conversion could only be achieved for low molecular weight starting materials (520 and 1,030 g mol⁻¹). The solution properties of the resulting materials were investigated by dynamic light scattering (DLS), showing the formation of large aggregates with size depending on the pH value. After deposition on a negatively charged mica surface, the structures observed by atomic force microscope (AFM) show the coexistence of aggregates and single macromolecules. Most interesting, in the case of the lower molecular weight sample (PG 520 g mol⁻¹), extended and ordered terrace structures were formed, which are unprecedented for hyperbranched polymers and are of interest for surface modification in general.     

LETTUCE SEED GERMINATION: EFFECTS OF HIGH TEMPERATURE AND OF REPEATED FAR-RED TREATMENT IN RELATION TO PHYTOCHROME

Abstract— At 37°C the active form of phytochrome in lettuce seed cannot function to promote subsequent germination. This effect of high temperature is distinct from thermal acceleration of dark reversion from the active form of phytochrome to the inactive form, and may be due to reversible denaturation of phytochrome.
Repeated brief irradiations with far-red light inhibit subsequent germination in the whole seed, whereas a similar irradiation regime results in a strong enhancement of the development of growth potential (ability to expand against an externally-imposed osmotic restraint) in the excised axial portion of the seed. A possible explanation for these two opposing results, in volving two different pigment systems with effective loci in different parts of the seed, is suggested.     

Umsetzung von Metall- und Metalloidverbindungen mit mehrfunktionellen Molekülen,XIX. Synthese von Amidoborazinen

Reaction of Metal and Metalloid Compounds with Polyfunctional Molecules. XIX. Synthesis of Amidoborazines By reaction of 2-chloro-1,3,4,5,6-pentamethylborazin with silylated carbonic acid amides and thioamides resp. the corresponding amidoborazines are obtained. By reaction of lithiated hexamethyldisilazane with 2-chloro-1,3,4,5,6-pentamethylborazine, the 2-hexamethyldisilazanyl-1,3,4,5,6-pentamethylborazine is formed. ¹H, ¹¹B, and ¹⁹F n.m.r. spectra, mass spectra and characteristic i.r. group frequencies are reported.     

A modular approach toward functionalized three-dimensional macromolecules: from synthetic concepts to practical applications

A new strategy for the preparation of functional, multiarm star polymers via nitroxide-mediated "living" radical polymerization has been explored. The generality of this approach to the synthesis of three-dimensional macromolecular architectures allows for the construction of nanoscopically defined materials from a wide range of different homo, block, and random copolymers combining both apolar and polar vinylic repeat units. Functional groups can also be included along the backbone or as peripheral/chain end groups, thereby modulating the reactivity and polarity of defined portions of the stars. This modular approach to the synthesis of three-dimensional macromolecules permits the application of these tailored materials as multifunctional hosts for hydrogen bonding, nanoparticle formation, and as scaffolds for catalytic groups. Examples of applications of the functional stars in catalysis include their use in a Heck-type coupling as well as an enantioselective addition reaction.     

Die Veresterungsgeschwindigkeiten der Nitrobenzoesäuren in Äthylenglykol und der Naphtoesäuren in Glyzerin

Zusammenfassung Es werden die monomolekuren Geschwindigkeitskonstanten der durch Chlorwasserstoff katalysierten Veresterung der Nitrobenzoesäuren in Glykol und der Naphthoesäuren in Glyzerin bei 25° gemessen und als Funktionen der Wasser- (w) und Salzsäurekonzentration (c) des Mediums durch Intrapolationsformeln dargestellt.Diese Konstanten nehmen in wasserwarmem Glyzerin und Glykol und in wasserreicherem Glyzerin proportional der Chlorwasserstoffkonzentration zu, in wasserreicherem Glykol aber rascher, was mit früheren Beobachtungen übereinstimmt. Fürc=1/6 undw=0.065 ist das Verhältnis der monomolekularen Konstanten der Benzoesäure zu jenen dero-,m- undp-Nitrobenzoesäure und der- und-Naphthoesäure in Äthylalkohol 10.0540.570.700.391.00, in Glykol 10·0380·690·79, in Glyzerin 10·0680·630·800·610·93. Die sterische Hinderung durch die Orthosubstitution ist somit hier in Glyzerin kleiner, in Glykol größer als in Äthylalkohol. Daher wird auch die Orthonitrobenzoesäure in Glyzerin rascher als in Glykol verestert, während sonst meist das umgekehrte Verhältnis besteht.Bei geringem Wassergehalt sind die Veresterungsgeschwindigkeiten in beiden Medien kleiner als in Äthylalkohol, bei größerem aber größer wegen der weitaus stärkeren verzögernden Wirkung des Wassers in letzterem.Unter den Versuchsbedingungen findet praktisch vollständige Veresterung statt, so daß die Wiederverseifung nicht zu berücksichtigen ist.Bei 183° verläuft die Selbstveresterung der Naphthoesäuren in Glyzerin ebenso wie die der bisher gemessenen Säuren nach der Gleichung für sesquimolekulare Reaktionen, deren Konstanten in Glyzerin, das etwa zwei Mole Wasser im Liter enthält, um rund 20% kleiner sind als in ursprünglich absolutem. In letzterem sind sie bei der-Naphthoesäure neunmal, bei der-Naphthoesäure elfmal kleiner als bei der Benzoesäure, woraus geschlossen wird, daß diese in Glyzerin von 183° nicht nur stärker als die-, sondern auch als die-Naphthoesäure dissoziiert sein muß, falls es sich bei der Selbstveresterung hauptsächlich um eine Wasserstoffionenkatalyse handelt.In Glyzerin und Glykol bei 25° über die Geschwindigkeit der Chlorhydrinbildung ausgeführte Versuche bestätigen den Befund von Kailan und Goitein.     

A study of [Co2(alkyne)(binap)(CO)4] complexes (BINAP=(1,1'-binaphthalene)-2,2'-diylbis(diphenylphosphine))

Understanding the interaction of chiral ligands, alkynes, and alkenes with cobaltcarbonyl sources is critical to learning more about the mechanism of the catalytic, asymmetric Pauson-Khand reaction. We have successfully characterized complexes of the type [Co2(alkyne)(binap)(CO)4] (BINAP=(1,1'-binaphthalene)-2,2'-diylbis(diphenylphosphine)) and shown that diastereomer interconversion occurs under Pauson-Khand reaction conditions when alkyne=HC[triple bond]CCO2Me. Attempts to isolate [Co2(alkyne)(binap)(CO)x] complexes with coordinated alkenes led to the formation of cobaltacyclopentadiene species.     

Optisch aktive übergangsmetall-komplexe : XXV. Substituenteneinflüsse auf die intramolekulare epimerisierung von tetragonal-pyramidalen molybdanund wolfram-komplexen

The synthesis, IR, ¹H NMR and UV spectra of optically active square pyramidal cyclopentadienyldicarbonyl-molybdenum and -tungsten complexes with Schiff bases, derived from methyl-substituted pyridine carbaldehyde(2) and S-(—)-α-methylbenzylamine, are described. The epimerisation of these complexes, measured polarimetrically at 75–97°C in DMF, follows a 1^st order rate law and represents a regular pentatopal skeletal rearrangement. The inductive effect of a methyl group in the para position of a pyridine ring leads to a retardation of the epimerisation compared to unsubstituted complexes. The rate constants decrease even more if an ortho methyl group is introduced into the pyridine system, since additional steric effects are introduced. If the metal complex contains a 4,6-dimethyl-substituted Schiff base as a chelating ligand, the contributions of a 4- and a 6-methyl group are additive. A benzene ring fused to the 5,6-positions of the pyridine system also leads to stabilisation of the configuration.     

Molecular aspects of superconductivity: The role of the one-particle term at the gap formation

An exact solution for the electron-vibrational problem of the nonadiabatic molecular system has been obtained. By the quasi-particle transformation technique, the fermionic Hamiltonian has been derived and solved at the ab initio level. Results clearly and unambiguously show that the gap formation due to nonadiabatic electron–phonon coupling is mediated by the one-particle electron–phonon interaction term, whereas the two-particle one represents just a correction to the correlation energy. The temperature dependence of the gap and electronic specific heat connected with the electron–phonon coupling have also been derived.     

Covalent chemistry and conformational dynamics of topologically chiral amide-based molecular knots

The readily available in gram quantities tris(allyloxy)knot of the amide-type 5 (knotane) can be completely and partially deprotected with nBu(3)SnH in the presence of a palladium catalyst resulting in hydroxyknotanes 7-9. These, in turn, react with diethylchlorophosphate giving rise to knotanes equipped with between one and three phosphoryl groups. Sulfonylation of bis(allyloxy)monohydroxyknotane 8 with p-toluenesulfonyl chloride and, following removal of one or two allyl groups from the intermediate monosulfonate 13, give rise to sulfonyloxy-allyloxy-hydroxy- and sulfonyloxy-dihydroxy-knotanes 15 and 14, respectively. This provides a convenient method for the preparation of knotanes with any substitution pattern. All new knotanes have been isolated in preparative amounts and as highly pure substances with an exception of allyloxy-dihydroxyknotane 9. This compound could only be obtained as a mixture with the corresponding monohydroxy-derivative 8. The structures of all synthesized compounds were established by means of FAB and MALDI TOF mass spectrometry, (1)H and (31)P NMR spectroscopy. The triphosphorylated knotane 10 exhibits high solubility in alcohols, allowing its complete enantiomeric resolution with a commercially available chiral HPLC column. (1)H,(1)H DQF-COSY correlation spectroscopy along with H/D exchange experiments and ab initio calculations provided the first detailed (1)H NMR signal assignments of knotanes in [D(6)]DMSO solution. The combination of variable temperature (1)H and (31)P NMR spectroscopy and molecular modeling has been applied to study the conformational behavior of the new knotanes in different solvents. It has been shown that in DMSO solution at room temperature knotanes exist in a relatively rigid nonsymmetrical conformation similar to that found in the solid state while faster conformational exchange leading to the average D(3) symmetrical structure was detected in a number of other solvents.