Synthesis, identification and quantification of oligomers from polyester coatings for metal packaging.

Polyester can coatings protect both food and packaging from mutual contamination. Even though, can coatings may release Non-Intentionally Added Substances (NIAS) in addition to Intentionally Added Substances (IAS). As NIAS are mainly constituted by cyclic or linear side products that are formed during the polymerization process, we focused our attention on these oligomeric species of molecular weight <1000 Da. These oligomers were obtained from two different polyester resins, each synthesized from four monomers (two phthalic acids and two diols), and from the corresponding final enamel can coatings using ethanol at 95% and 50% at 60 °C for 4 h and 10 days, respectively, as food simulants. HPLC-ESI-MS analysis on the extracts allowed identifying various cyclic and linear oligomers. For the conclusive identification of the different oligomers and their isomeric structures, ad hoc standards were synthesized by acylation reaction between alkyl diols and phthaloyl chlorides. By comparison of 1H NMR spectra, linear and cyclic oligomers were characterized by finding the major presence of 2 + 2 cyclic compounds. The 16 synthesized standards, 4 linear and 12 cyclic compounds were used to establish a method for quantification of linear and cyclic oligomers in enamel migration samples by micro HPLC-high-resolution MS (HRMS). The results showed no significant differences between the amounts of cyclic oligomers extracted with both ethanol concentrations (50 and 95%) and time contact. The extracts showed only a small amount of linear compounds and a prevalence of 2 + 2 cyclic oligomers. The work shows the great importance of the synthesis of specific standards to allow exact quantification in food contact material migrates.

Aminofluorination of 2-alkynylanilines: a Au-catalyzed entry to fluorinated indoles.

The scope and limitations of gold-catalyzed tandem cycloisomerization/fluorination reactions of unprotected 2-alkynylanilines to have access to 3,3-difluoro-2-aryl-3H-indoles and 3-fluoro-2-arylindoles are described. An unprecedented aminoauration/oxidation/fluorination cascade reaction of 2-alkynylanilines bearing a linear alkyl group on the terminal triple bond is reported.

Brønsted acid catalyzed cascade reactions of 2-[(2-aminophenyl)ethynyl]phenylamine derivatives with aldehydes: a new approach to the synthesis of 2,2'-disubstituted 1H,1'H-3,3'-biindoles.

An unusual Brønsted acid catalyzed cascade reaction of 2-[(2-aminophenyl)ethynyl]phenylamine derivatives with aryl(heteroaryl)aldehydes to afford an efficient alternative entry into 2,2'-disubstituted-1H,1'H-3,3'-biindoles under metal-free conditions is reported.

One-pot gold-catalyzed aminofluorination of unprotected 2-alkynylanilines.

A tandem gold(I)-catalyzed aminocylization/fluorination and a two-step, one-pot gold(III)-catalyzed cyclization/electrophilic fluorination provide a convenient and general method for the synthesis of 3,3-difluoro-2-substituted-3H-indoles in good yield under mild conditions. Extension of the procedure to the synthesis of 2-aryl-3-fluoro-1H-indoles is described. The reaction proceeds smoothly in green ethanol and does not require any base, acid, or N-protective group.

An alternative one-pot gold-catalyzed approach to the assembly of 11H-indolo[3,2-c]quinolines.

A new one-pot approach was developed to construct the 11H-indolo[3,2-c]quinoline scaffold through a gold-catalysed reaction of 2-[(2-aminophenyl)ethynyl]phenylamine derivatives with aldehydes. The broad scope and the high regioselectivity of this new protocol as well as the mild and neutral reaction conditions make it a viable alternative to the previously reported procedures.