In
this work, we investigated the possible use of polylactide (PLA),
a biodegradable polymer obtained from renewable biofeedstock, to produce
a range of industrially useful lactic acid esters. We describe a simple
and convenient solvothermal alcoholysis method for large-scale recycling
of PLA resins or residues from disposable packaging in the presence
of the appropriate alcohol under catalyst-free or catalytic conditions.
This process proceeds easily both without and with a catalyst. The
results show that the best catalytic activities involve magnesium
and calcium alkoxides synthesized in situ from organometallic or metallic
precursors and an alcohol. We determined the crystal structure of
the chiral mononuclear postcatalyst [Ca(LAc)2(EL)2] (1; LAc = lactic acid anion, EL = ethyl lactate),
obtained directly from the reactor. Particular emphasis is placed
on the operating conditions and high activity of the catalyst used.
Key factors that affect the catalytic activity and reaction mechanism
are also highlighted.
Furan-fused oxatriphyrin(3.1.1) acts as a ligand towards boron(III), phosphorous(III), and phosphorous(V) ions. The coordination abilities are adjusted by changes of the oxidation state. Two coordination modes are possible, depending on the central-ion entrapped in the oxatriphyrin(3.1.1) environment. A free base, structurally similar to the complexes, can be easily obtained by regioselective reduction. The resulting molecules are highly emissive after conversion into a phlorin-like oxatriphyrin(3.1.1) frame (NON donors), and show chiral activity caused by the presence of a tetrahedral carbon.
The effect of alkaline-earth-metal alkoxides on the protonolysis of CpM'Cl (M' = Ti, Zr, Hf; Cp = cyclopentadiene) was investigated. This approach enabled the design of compounds with well-defined molecular structures to generate high-purity binary metal oxides. Single-source molecular precursors with structures of [MM'(μ-OEt)(μ-OEt)(OEt)(EtOH)] with M = Mg and M' = Ti (1), Zr (2), and Hf (3), [CaTi(μ-O)(μ-O)(μ-OEt)(OEt)(EtOH)Cl] (4), and [MM'(μ-O)(μ-OEt)(OEt)(EtOH)Cl] with M = Ca and M' = Zr (5) and Hf (6) were prepared via elimination of the cyclopentadienyl ring from CpM'Cl as CpH in the presence of M(OEt) and ethanol (EtOH) as a source of protons. Meanwhile, similar reactions involving the initial substitution of Cl ligands by OEt groups in CpM'Cl (M' = Ti, Zr, Hf) resulted in the formation of [MM'(μ-OEt)(μ-OEt)(OEt)(EtOH)] with M = Ca and M' = Ti (7), Zr (8), and Hf (9). The precursors were characterized by elemental analysis, NMR spectroscopy, and single-crystal X-ray structural analysis. Magnesium compounds 1-3 decomposed at 750-850 °C to give MgTiO along with small amounts of MgTiO, MgZrO, or MgHfO binary metal oxides. The thermolysis of calcium compounds 4 and 7-9 led to highly pure CaTiO, CaZrO, or CaHfO perovskite-like oxide particles with diameters of 20-30 nm.
Be independent: Under basic conditions a furan ring entrapped in an aromatic macrocycle readily recovered the properties characteristic for a free molecule and assimilated a water molecule forming the Achmatowicz rearrangement product with a 3‐pyranone subunit built in. Coordination of palladium(II) created a complex stabilizing the second tautomer with two sp3 carbon atoms (oxygen red, water green, palladium purple, and the aryl group blue).
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