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The chemical depolymerisation of poly(bisphenol A carbonate) (BPA-PC) was studied using α-hydroxyketones as nucleophiles to give bisphenol A as the original monomer and the corresponding vinylene carbonates as co-products. The optimisation revealed that 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) is an efficient organocatalyst to perform this reaction under mild conditions (25 °C in 2-MeTHF). The success of TBD was attributed to the fact that it can both activate α-hydroxyketones and BPA-PC, through hydrogen bonding. The substrate scope was then investigated with a range of α-hydroxyketones to give vinylene carbonates (symmetrical and unsymmetrical, aromatic, heteroaromatic and alkyl) with moderate to high yields (30–97%, 13 examples). Scale-up experiments were also conducted to highlight the synthetic utility of this method. Finally, it was demonstrated that vinylene carbonates can be produced from waste polycarbonate contained in compact disks (CDs) and other BPA-PC containing materials, thus providing a safe and economical access to these species. [ABSTRACT FROM AUTHOR]

The selective oxidation of α,α-diglycerol was studied using oxygen as a clean oxidant in the presence of a palladium/neocuproine complex. After optimization of the reaction parameters, the mono-oxidation product was obtained with 93% NMR yield (up to 76% isolated yield). The product was named "diglycerose" considering that it mainly exists as a cyclic hemi-ketal form. [ABSTRACT FROM AUTHOR]

The α-alkylation of acetophenone with benzyl alcohol through borrowing hydrogen has been studied using nickel catalysis. Ni/SiO2-Al2O3 was found to be the best catalyst for this transformation and the corresponding alkylated acetophenone was obtained with 93% isolated yield. Following the objectives of clean and sustainable chemistry, the reaction occurs under solvent-free conditions and requires only a catalytic amount of base. This protocol was next applied to a wide range of ketones and alcohols and the desired products were isolated with 18–86% yields (26 examples). The recovery and recyclability of the nickel catalyst was also investigated and it was found to be active over 5 runs without significant loss of activity. Surprisingly, the active catalyst appears to include an amorphous nickel hydroxide layer. [ABSTRACT FROM AUTHOR]

Herein, the preparation of methyl oleate α-hydroxyketone from the corresponding 1,2-diol was investigated using both homogeneous and heterogeneous systems. Homogeneous conditions using a Pd(OAc)2/neocuproine complex were first developed using oxygen as a sole oxidant under mild conditions (MeOH, 50 °C). Under these conditions, the conversion of diol reached 95%, and α-hydroxyketone was obtained with 97% selectivity. The access to α-hydroxyketone has also been studied by dehydrogenation using a range of heterogeneous catalysts under solvent-free conditions at high temperatures (160–180 °C). Dehydrogenation using activated Ru/C under vacuum provided α-hydroxyketone with 93% conversion and 82% GC yield. The optimized conditions were applied to a range of oleochemical diols, including a vegetable oil derivative, to obtain the corresponding α-hydroxyketones with up to 74% isolated yields. [ABSTRACT FROM AUTHOR]

Amphiphilic sorbitan acetals have been prepared from sorbitan by acetalisation using linear aliphatic aldehydes or by transacetalisation starting from the corresponding aldehyde diethylacetals. A series of sorbitan acetals has been obtained with 29–81% isolated yields. It has been shown that these sorbitan acetals exist as a mixture of five-membered and six-membered regioisomers. Hydrogenolysis of the mixtures gave the corresponding sorbitan ethers as a mixture of 3 regioisomers with 55–85% isolated yields. A one-pot two-step procedure was also optimized from sorbitan giving similar results. The amphiphilic properties of sorbitan acetals and ethers were evaluated and both families exhibit interesting surfactant properties. [ABSTRACT FROM AUTHOR]

A direct synthesis of paracetamol (acetaminophen) from hydroquinone has been developed using ammonium acetate as an amidating agent. The reaction proceeds in acetic acid at elevated temperatures without any metallic catalyst. Under these conditions, paracetamol was obtained with high yield and selectivity (>95%). The reaction has also been carried out on the multi-gram scale (44 g of hydroquinone) and a potential process has been proposed based on the recycling of the solvent and by-products. This amidation protocol has also been extended to other phenol derivatives. [ABSTRACT FROM AUTHOR]

The catalytic activity and enantioselectivity in the kinetic resolution of (±)-1-naphthylethanol with a range of structurally related 3,4-dihydropyrimido[2,1-b]benzothiazole-based catalysts is examined. Of the isothiourea catalysts screened, (2S,3R)-2-phenyl-3-isopropyl substitution proved optimal, giving good levels of selectivity in the kinetic resolution of a number of secondary alcohols (S values up to >100 at ~50% conversion). Low catalyst loadings (0.10-0.25 mol%) of the optimal isothiourea can be used to generate enantiopure alcohols (>99% ee) in good yields.

Cascade reaction sequences incorporating N-heterocyclic carbene-based organocatalysis have been developed that allow the direct preparation of a range of (+/-)-4-phenoxycarbonylazlactones in good isolated yields (66-84%) from the corresponding N-p-anisoyl amino acids.

N-Heterocyclic carbenes promote the formal [2+2] cycloaddition of ketenes with N-tosyl imines to give the corresponding beta-lactams in good to excellent isolated yields; chiral NHCs give beta-lactams in high e.e. after crystallisation.