Solvothermal Alcoholysis Routes for Recycling Polylactide Waste as Lactic Acid Esters

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] (<b>1</b>; 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

Synthesis and Structural Characterization of Magnesium Drug Complexes: Efficient Initiators for Forming Polylactide–Drug Conjugates

Five novel magnesium alkoxides supported by drug chelating agents <i>pridinolum</i> (PriOH = 1,1-diphenyl-3-(1-piperidinyl)-1-propanol) and <i>venlafaxinum</i> (VenlOH = (<i>RS</i>)-1-[2-dimethylamino-1-(4-methoxyphenyl)-ethyl]­cyclohexanol) were successfully synthesized and characterized. Direct reaction of PriOH and VenlOH with MgBu₂ (1:1) in toluene gives the dimeric compounds [Mg­(μ,η²-OPri)^<i>n</i>Bu]₂ (<b>1</b>) and [Mg­(μ,η²-VenlO)^<i>n</i>Bu]₂ (<b>2</b>), respectively. Furthermore, the crystallization of an equimolar mixture of <b>1</b> and <b>2</b> in toluene yields heteroleptic magnesium complex [Mg­(μ,η²-OVenl)­(η¹-OPri)]₂ (<b>3</b>). Moreover, reactions of <b>1</b> and <b>2</b> with 2 molar equivs of the corresponding drug–ligands give the homoleptic magnesium bis-alkoxides [Mg­(μ,η²-OPri)­(η¹-OPri)]₂ (<b>4</b>) and [Mg­(μ,η²-OVenl)­(η¹-OVenl)]₂ (<b>5</b>). The treatment of compound <b>1</b> with 2 equivs of VenlOH or <b>2</b> with 2 equivs of PriOH leads to the formation of <b>3</b>. Complexes <b>1</b>–<b>5</b> were characterized by elemental analysis, nuclear magnetic resonance, and single crystal X-ray diffraction (for <b>1</b>–<b>4</b>). It was found that complexes <b>1</b>–<b>5</b> are efficient initiators of the ring-opening polymerization of l-LA, yielding PLA-OPri and PLA-OVenl conjugates, respectively. Moreover, the ring-opening polymerization of l-LA initiated by <b>3</b> led to the simultaneous generation of a blend of poly-l-lactide conjugates with end-capped VenlO and PriO groups

Molecular Routes to Group IV Magnesium and Calcium Nanocrystalline Ceramics

The effect of alkaline-earth-metal alkoxides on the protonolysis of Cp₂M′Cl₂ (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 [M₂M′₂(μ₃-OEt)₂(μ-OEt)₄(OEt)₆(EtOH)₄] with M = Mg and M′ = Ti (<b>1</b>), Zr (<b>2</b>), and Hf (<b>3</b>), [Ca₆Ti₄(μ₆-O)₂(μ₄-O)₂(μ₃-OEt)₁₂(OEt)₁₂(EtOH)₆Cl₄] (<b>4</b>), and [M₂M′₂(μ₄-O)­(μ-OEt)₅(OEt)₄(EtOH)₄Cl]_<i>n</i> with M = Ca and M′ = Zr (<b>5</b>) and Hf (<b>6</b>) were prepared via elimination of the cyclopentadienyl ring from Cp₂M′Cl₂ as CpH in the presence of M­(OEt)₂ and ethanol (EtOH) as a source of protons. Meanwhile, similar reactions involving the initial substitution of Cl ligands by OEt groups in Cp₂M′Cl₂ (M′ = Ti, Zr, Hf) resulted in the formation of [M₂M′₂(μ₃-OEt)₂(μ-OEt)₄(OEt)₆(EtOH)₄] with M = Ca and M′ = Ti (<b>7</b>), Zr (<b>8</b>), and Hf (<b>9</b>). The precursors were characterized by elemental analysis, NMR spectroscopy, and single-crystal X-ray structural analysis. Magnesium compounds <b>1</b>–<b>3</b> decomposed at 750–850 °C to give MgTiO₃ along with small amounts of Mg₂TiO₄, Mg₂Zr₅O₁₂, or Mg₂Hf₅O₁₂ binary metal oxides. The thermolysis of calcium compounds <b>4</b> and <b>7</b>–<b>9</b> led to highly pure CaTiO₃, CaZrO₃, or CaHfO₃ perovskite-like oxide particles with diameters of 20–30 nm