Linear polymers with monodendron side groups adsorb on highly oriented pyrolytic graphite (HOPG) in a remarkably regular pattern. The wormlike molecules have been depicted individually by scanning force microscopy with their long axis aligned according to the 3-fold symmetry of HOPG. The positional and orientational order of the adsorbed molecules is explained by the specific interaction of the alkyl substituents of the monodendrons with the HOPG surface. Direct evidence of the epitaxial adsorption was found by scanning tunneling microscopy of monolayers of the monomeric dendrons on HOPG. Ordering depended on the number of the alkoxy substitutes on the monodendrons. If the substitution of the monodendrons by the alkoxy groups was too dense, regular adsorption of the alkyl tails was impeded.

A series of Pd(II) complexes containing chiral diamine ligands were investigated as asymmetric catalysts for the rearrangement of allylic imidates to allyl amides. The best catalysts were cations obtained by dechlorination of dichloro[(S)-2-(isoindolinylmethyl)-N-methylpyrrolidine]palladium(II) (17) with silver salts in CH2Cl2. Catalyst 18 was studied thoroughly and shown by 1H NMR and X-ray crystallography analysis to be a C 1 symmetric dimer (Figure ). A series of related catalysts 22−27 having various counterions and anionic ligands were also prepared and studied as asymmetric catalysts for the rearrangement of allylic N-(4-trifluorophenyl)benzimidate 29 to allylic benzamide 30 (eq 4). Rearrangement of 29 in CH2Cl2 (48 h at 40 °C) in the presence of 5 mol % of 18 affords (−)-30 in 69% yield and 55% ee. Enantioselection is increased to 60% when an isomerically pure sample of 18 is employed. Chemical correlation of allylic benzamide 30 with (R)-norvaline established that (−)-30 has the R absolute configuration (Scheme ). A cyclization-induced rearrangement mechanism (Scheme ) requires that in the major pathway the imidate nitrogen attacks the re face of the olefin with Pd coordinated to the si face. These studies constitute the first report of asymmetric catalysis of the rearrangement of allylic imidates to allylic amides. However, significant hurdles remain to be overcome before the enantioselective rearrangement of allylic imidates becomes a practical route to enantioenriched nitrogen compounds.

Functional membranes containing spatially ordered, structurally defined, ion-selective pores are fundamental building units in biology, but present a synthetic challenge

Synthesis and characterization of methacrylate-monofunctionalized crown ether compounds based on derivatives of 2-hydroxymethyl-l,4,7,10,13-pentaoxacyclopentadecane and 4'-hydroxymethyl-1,4,7,10,13-pentaoxabenzocyclopentadecane is described. By differential scanning calorimetry (DSC) and thermooptical analysis (TOA) it is shown that the synthesized compounds and their sodium triflate complexes exhibit columnar mesophases.