Phosphazene base-catalyzed intramolecular cyclization for efficient synthesis of benzofurans via carbon-carbon bond formation.

An organic superbase, phosphazene P4-(t)Bu, functioned as an active catalyst for intramolecular cyclization of o-alkynylphenyl ethers via carbon-carbon bond formation to provide an efficient synthetic method for 2,3-disubstituted benzofurans derivatives under mild reaction conditions without the need for a metal catalyst.

Electron diffraction of ABX3 perovskites with both layered ordering of A cations and tilting of BX6 octahedra.

It is shown that 21 ABX(3) perovskites with tilted BX(6) octahedra and layered ordering of A cations can be generated on the basis of group-subgroup relations. These structures (with 16 different space groups) are classified into ten diffraction types in terms of the conditions for superstructure reflections caused by the ordering of A cations, tilting of BX(6) octahedra and structural absences. SAED (selected-area electron diffraction) allows the distinction of seven of the 21 different perovskites, while additional symmetry analysis by CBED (convergent-beam electron diffraction) is needed for the remaining 14 structures. The space groups of lithium lanthanum titanate pseudomorphs (with discrete chemical compositions) are successfully deduced by electron diffraction experiments.