Über Synthesen von alkylsubstituierten m-Aminophenolen aus o-Benzochinol-acetaten

Zusammenfassung Zur Synthese substituierter m-Aminophenole sind die durch Bleitetraacetat-oxydation von substituierten Phenolen zugänglichen o-Benzochinol-acetate geeignet¹. Ein Weg besteht in der Überführung der aus diesen Verbindungen leicht zugänglichen m-Hydroxybenzonitrile² in die entsprechenden m-Hydroxybenzoesäuren, die dann nach demSchmidt-Abbau¹² das Amin liefern.Beimzweiten Weg wird Phthalimid oder Succinimid mit dem o-Benzochinol-acetat in Reaktion gebracht. Die so entstandenen m-Phthalimino- bzw. m-Succiniminophenole können leicht in die freien Aminophenole umgewandelt werden.Voraussetzung für die Durchführbarkeit dieser Reaktion ist die Gegenwart einer zur Hydroxylgruppe o-ständigen Alkyloder Arylgruppe im ursprünglichen Phenol.     

Slow paramagnetic relaxation versus magnetic ordering of high-spin iron III in trigonal bipyramidal environments: Hyperfine splitting of the low temperature Mössbauer spectra of some high symmetry chloroferrate anion salts, [FeCl 5 2− ] and [FeCl5(CH3OH)2−]

A combination of Iron-57 Mössbauer spectroscopy and magnetic susceptibility measurements are used to show that the [FeCl₅ ^2–] and [FeCl₅-(CH₃OH)^–2] anions (stabilized in the solid state by large quaternary cations) undergo ferromagnetic order, T_critical6 K.     

Click-connected ligand scaffolds: macrocyclic chelates for asymmetric hydrogenation

Click chemistry is used to construct ligand scaffolds for a series of chiral diphosphites. Enantioselectivity as high as 97% ee is obtained using these click ligands in rhodium-catalyzed asymmetric hydrogenation. Control experiments and spectroscopic data suggest that a 16-membered P,P-macrocyclic Rh(I) chelate is formed.     

Efficient amide-directed catalytic asymmetric hydroboration

A series of acyclic beta,gamma-unsaturated amides are shown to undergo highly regio- (>95%) and enantioselective (93-99% ee) rhodium-catalyzed hydroboration with pinacolborane (PinBH) using simple chiral monophosphite or phosphoramidite ligands in combination with Rh(nbd)2BF4. The most effective ligands identified are phosphoramidite 4, derived from BINOL and N-methylaniline, and phosphite 5c, prepared from the (4'-tert-butyl)phenyl TADDOL analogue and phenol. For example, (E)-3-hexenoic acid phenylamide ((E)-1) undergoes rhodium-catalyzed hydroboration with PinBH (0.5 mol % Rh(nbd)2BF4, 1.1 mol % BINOL-derived phosphoramidite 4, THF, 40 degrees C, 2 h) affording an intermediate boronate ester which after oxidation with basic hydrogen peroxide gives the beta-hydroxy amide, (S)-3-hydroxyhexanoic acid phenylamide ((S)-3), in good yield (80%) and high enantiomeric purity (99% ee). Isomeric disubstituted (E)- and (Z)-alkenes give nearly identical results, and a trisubstituted alkene substrate is also shown to undergo efficient hydroboration (97% ee). Moderate catalyst loading (0.5 mol %) and reaction temperatures in 25-40 degrees C range are generally effective. N-Phenyl amides are generally more efficient than the corresponding N-benzyl or N,N-dibenzyl analogues. Pinacolborane is found to be more efficient than catecholborane.