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Aromatic oligoamides adopting helical conformations are synthesized by coupling carboxyl-terminated basic units having two, four, and eight residues to amine-terminated oligomer precursors. Coupling yields show no noticeable reduction with the size of the

(Chemical Equation Presented) The hydrogen bond rigidified backbones of aromatic oligoamides are temporarily interrupted by replacing the amide hydrogens with the acid-labile 2,4-dimethoxybenzyl (DMB) group, which allows the efficient preparation of long

Under mild conditions, trialkylalanes (Et3Al and Bu i3Al) in chlorine-containing solvents (CH 2Cl2 or ClCH2CH2Cl) react with cyclic acetals and orthoformates to form glycol monoethers and dialkylacetals, respectively, in high yields. The 1H NMR spectroscopic data demonstrate that CH2Cl2 or ClCH2CH 2Cl interacts with Bui3Al.

Ethylene acetals and ethylene ketals undergo reductive scission under the action of Bui2AlH in the presence of catalytic amounts of ZrCl4. With Et3Al and Bui3Al, reductive alkylation also occurs.

There are reports on the reduction of ethylene glycol acetals and ketals by aluminum hydrides to the corresponding monoethers. Considering that these compounds find wide application as solvents, plasticizers, and perfume ingredients, it was of interest to study the possibility of a selective hydrogenation of different 1,3-dioxacycloalkanes by industrial grade mixtures of diethylaluminum hydride and triethylaluminum. According to the data obtained for the reactions with cyclic acetals, triethylaluminum is 1. 5-2 times more active than diethylaluminum hydride. The activities of the five-membered ring acetals and ketals in the reduction and alkylation processes are similar; 2-phenyl-1, 3-dioxolane has the highest reactivity. Thus, 2-mono- and 2,2-disubstituted 1,3-dioxacyclanes form monoethers of the correepsponding diols by the action of diethylaluminum hydride and triethylauminum. In the case of triethylaluminum, ethylation of the carbon atom adjacent to the two oxygen atoms takes place.