RESUMO
A Brønsted acid catalyzed aza-Friedel-Crafts reaction of indolizines with 3-hydroxyisoindolinones has been established, which constructs isoindolinone derivatives bearing a tetrasubstituted stereocenter in good to high yields and enantioselectivities. Notably, this strategy provides a new access to C1-functionalization of indolizines with excellent regioselectivities. Moreover, this intriguing C1-regioselective transformation was induced under thermodynamic control.
RESUMO
An asymmetric [3+3] cyclization of nitroenynes and 3-pyrrolyloxindoles has been realized with a chiral bifunctional squaramide catalyst. This Michael/Friedel-Crafts cascade strategy provides a facile and efficient access to enantioenriched polycyclic aza-spirooxindoles with 32-95% isolated yields and excellent stereocontrol under mild reaction conditions.
RESUMO
Three-dimensional open porous graphitic carbon nitride with cyano groups (3D OPG-C3N4-CN) has been fabricated by a facile two-step process that combines NaCl-assisted freeze-drying with calcination. NaCl not only works as a template for the 3D open porous structure, but also facilitates the decomposition of g-C3N4 around 500 °C to some extent. Meanwhile, a moderate amount of cyano groups acting as electron capture centers are introduced at the edge of the 3D open porous g-C3N4 during the formation process. Compared with bulk g-C3N4 without NaCl assistance, the 3D OPG-C3N4-CN exhibits improved light absorption, reduced carrier recombination and more active sites. As a result, the enhanced hydrogen production of 3D OPG-C3N4-CN reaches up to 1590 µmol h-1 g-1 when using Pt as a cocatalyst, which is about six times as much as that of the bulk g-C3N4.