New Functionalized Polycycles Obtained by Photocatalytic Oxygenation Using Mn(III) Porphyrins in Basic Media

According to our earlier observations, the products of photocatalytic oxygenations of furan and thiophene derivatives of benzobicyclo[3.2.1]octadiene with anionic and cationic manganese(III) porphyrin at pH = 7 strongly depended on the type and position of the heteroatom in the aromatic ring, as well as the charge of the photocatalyst. Hence, a significant pH increase (to 10) in these systems offered a reasonable tool to affect the diversity and yields of the oxygenation products. They were quantitatively separated by TLC and identified with NMR analyses. The results clearly indicated that the increase of HO− concentration, in most cases, considerably changed the product yield, e.g., enhanced it to 70% for the hydroxy-furyl derivative. Accordingly, the selectivity of the oxygenation of the furan compound could be improved in this way. In the case of one thienyl compound, however, even an additional product appeared, while the yields of the products of the other thiophene derivative (with cationic catalyst) decreased to zero, suggesting the application of lower pH for preparative purposes. The pH effects indicate that oxygenation reactions in these systems involve more photochemically generated oxidative agents, e.g., •OH and (P)Mn(V)=O), the role of which is affected by the pH increase in various ways.

Synthesis of a polycaprolactone-based material with shape-memory and mendability

new thermoset has been prepared from a bismaleimidic terminated polycaprolactone polyester and a tris-furan compound acting as a crosslinker via the Diels-Alder reaction between the furan and maleimide functionalities. Owing to the reversibility of the Diels-Alder chemistry and the increased mobility of the crosslinked polyester chains, this material had the ability to mend scratches under mild temperature conditions. The synthesized precursors and resulting crosslinked material were characterized using 1H NMR, FT-IR, GPC, TGA and DSC methods. The scratch mendability of the material was investigated using optical microscopy.

A gold-catalyzed 1,2-acyloxy migration/intramolecular cyclopropanation/ring enlargement cascade: syntheses of medium-sized heterocycles

A gold catalyzed 1,2-acyloxy migration/intramolecular cyclopropanation/ring enlargement cascade of furan substrates provides a new highly efficient procedure for the formation of ten and eleven-membered ring compounds. A new transformation type of intermolecular furan compound catalyzed by a gold catalyst was reported.