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A series of focally substituted organothiol dendrons of the first through third generation were used to construct adlayers on a gold surface. The presence and structural features of these adlayers were confirmed by X-ray photoelectron spectroscopy, infrared spectroscopy, and ellipsometry. The relative coverage and/or permeability of these adlayers was studied using capacitance and electrochemical blocking experiments. It was found that as the number of hyperbranches in the dendron increased from one to three, the dendron adlayers became initially less and then more permeable. This result indicated a tradeoff between size and packing efficiency when using these molecules to cover a surface. These data also suggest that the dendrons have formed homogeneous but permeable adlayers on the gold surface rather than adlayers consisting of islands of material. These adlayers showed large differences in their ability to trap and hold a small molecule, trans-cyclohexanediol, within them.

The reaction of preformed mixed acetals derived from (α-hydroxyalkyl)dimethylallylsilane with a number of aromatic and aliphatic aldehydes in the presence of Lewis acids results in a highly diastereoselective intramolecular allylation reaction. The reaction proceeds through a cyclic synclinal SE‘ addition of the allylsilane to an intermediate oxocarbenium ion. The reaction occurs exclusively by an intramolecular process as determined by means of a cross-over experiment. The relative stereochemistry was determined by the conversion of one of the allylation products to a known (stereodefined) aldol-type product. A greater degree of diastereoselectivity is obtained by in-situ formation of an oxocarbenium ion from (α-hydroxyhexyl)dimethylallylsilane and an aldehyde in the presence of boron trifluoride etherate. The diastereoselectivity of the in-situ allylation reaction typically exceeds 100:1 in favor of the syn adduct. However, reactions with electron rich aryl aldehydes resulted in a diminished degree of d...