Synthesis and Structures of Two 9,10-Dihydro-9,10-distannaanthracenes

The 9,9,10,10-tetramethyl- and 9,9,10,10-tetra- tert -butyl-9,10-dihydro-9,10-distannaanthracenes have been synthesized and characterized. The X-ray crystallographic analysis of 9,10-dihydro-9,10-distannaanthracenes showed that the central tricyclic framework of the tetramethyl derivative has a butterfly conformation with a dihedral angle of 143°, while the central six-membered ring of the tetra- tert -butyl derivative has a planar structure. The synthesis and structure of a novel tribenzostannepin are also described.