Monomolecular films of phenolic esters.
Abstract The properties of three phenolic esters, characterized by gradual changes in their molecular constitution, have been evaluated in pure monomolecular films, as well as in mixed films with stearic acid. The pressure-area isotherms for the pure compounds reflect a similar orientation for compounds I (resorcinol monoundecanoate) and II (4-chlororesorcinol 1-undecanoate) at the air-water interface. At pressures corresponding to the limiting area per molecule, the molecules are apparently rather erect and anchored to the aqueous subphase surface by the phenolic-OH function; at lower pressures, the molecules are less erect, with their aliphatic chains randomly intertwined. The isotherm characteristics for III (4-chlorophenyl undecanoate), on the other hand, are compatible with an orientation in which the molecule is anchored to the aqueous subphase surface by its ester function, with both the aliphatic chain and the substituted phenyl ring projecting upwards. Isotherms for 1:1 mixtures of each of the phenolic esters with stearic acid indicate that the properties of the mixed films were controlled, generally, by the esters (at low pressures) and by stearic acid (at high pressures), after the esters had been forced out of area-determining positions in the films. The experimentally derived isotherms for the mixtures were compared with those calculated from the isotherms of the pure components, and observed deviations from additive behavior discussed.
Effect of griseofulvin upon lipid films at the air-water interface.
The effect of griseofulvin upon monomolecular films of stearic acid and cholesterol has been determined by comparing the pressure-area curves obtained when these film-forming materials were spread on a redistilled water substrate and one consisting of a solution of griseofulvin in redistilled water.
Enantioselective Synthesis of Dihydropyrans. Catalysis of Hetero Diels−Alder Reactions by Bis(oxazoline) Copper(II) Complexes
C2-symmetric bis(oxazoline)−Cu(II) complexes 1 and 2 catalyze the inverse electron demand hetero Diels−Alder reaction of α,β-unsaturated carbonyl compounds (heterodiene) with electron-rich olefins (heterodienophile) in high diastereo- and enantioselectivity. α,β-Unsaturated acyl phosphonates and β,γ-unsaturated α-keto esters and amides are effective heterodienes, while enol ethers and sulfides function as heterodienophiles. A range of substitution patterns is possible on the heterodiene:  terminal alkyl, aryl, alkoxy, and thioether substituents are all tolerated. The enantioselective synthesis of dihydropyrans by this method has been shown to be straightforward:  cycloadditions may be conducted with as little as 0.2 mol % of the chiral catalyst and are readily run on multigram scale. The reactions exhibit a favorable temperature−enantioselectivity profile, with selectivities exceeding 90% even at room temperature. A simple reaction protocol that employs a solid air-stable catalyst, convenient reaction tem...