A Sequential Activation of Alkyne and C-H Bonds for the Tandem Cyclization and Annulation of Alkynols and Maleimides through Cooperative Sc(III) and Cp*-Free Co(II) Catalysis.

[4 + 2] oxidative Diels-Alder reaction of readily available alkynols with maleimide is achieved for the rapid access of pthalimide-fused multicyclic compounds. The reaction is proposed to go through a sequence of Sc(OTf)-catalyzed electrophilic cyclization, ligand exchange with Cp*-free cobalt, and C-H activation followed by maleimide insertion.

Evaluating the fracture toughness and flexural strength of pressable dental ceramics: an in vitro study.

The study was undertaken to evaluate the biaxial flexural strength, biaxial flexural strength after etching with 9 % HF acid and fracture toughness of three commonly used pressable all ceramic core materials. Ninety glass ceramic specimens were fabricated from three commercially available leucite based core ceramic material (1) Esthetic Empress, (2) Cergo, and (3) Performance Plus. Thirty discs of each material were divided into three groups of 10 discs each.