3 research outputs found
Heteroarylboronates in Rhodium-Catalyzed 1,4-Addition to Enones
RhodiumĀ(I)-catalyzed
1,4-addition of aryl and alkenylboronic acids
to Ī±,Ī²-unsaturated carbonyl compounds is well established,
but the transfer of heteroaryl residues in this reaction remains underdeveloped.
We have studied heteroaryl MIDA and pinacol boronates as alternatives
to the labile boronic acid counterparts. Under racemic conditions,
12 adducts with heteroaryl residues, among them unsubstituted 3- and
4-pyridinyl, 2-furanyl, thienyl, and pyrrolyl groups, were obtained
in moderate to excellent yields. The enantioselective version of the
reaction proved highly sensitive to the electronic character of the
heteroaryl substituents, with boronates carrying electron-rich residues
giving modest to high yields but consistently high enantiomeric excesses
Efficient Pseudo-enantiomeric Carbohydrate Olefin Ligands
Highly efficient pseudo-enantiomeric olefin ligands were designed from d-glucose and d-galactose. These ligands yield consistently excellent levels of enantioselectivity in Rh(I)-catalyzed 1,4-additions of aryl- and alkenylboronic acids to achiral enones and high diastereoselectivity with chiral substrates. Contrary to established olefin ligands, they are obtained enantiomerically pure via short syntheses without racemic resolution steps, making them a valuable addition to the arsenal of chiral ligands with olefinic donor sites
Conformal and Highly Luminescent Monolayers of Alq<sub>3</sub> Prepared by Gas-Phase Molecular Layer Deposition
The gas-phase molecular layer deposition
(MLD) of conformal and highly luminescent monolayers of trisĀ(8-hydroxyquinolinato)Āaluminum
(Alq<sub>3</sub>) is reported. The controlled formation of Alq<sub>3</sub> monolayers is achieved for the first time by functionalization
of the substrate with amino groups, which serve as initial docking
sites for trimethyl aluminum (TMA) molecules binding datively to the
amine. Thereby, upon exposure to 8-hydroxyquinoline (8-HQ), the self-limiting
formation of highly luminescent Alq<sub>3</sub> monolayers is afforded.
The growth process and monolayer formation were studied and verified
by in situ quartz crystal monitoring, optical emission and absorption
spectroscopy, and X-ray photoelectron spectroscopy. The nature of
the MLD process provides an avenue to coat arbitrarily shaped 3D surfaces
and porous structures with high surface areas, as demonstrated in
this work for silica aerogels. The concept presented here paves the
way to highly sensitive luminescent sensors and dye-sensitized metal
oxides for future applications (e.g., in photocatalysis and solar
cells)