Pd-Catalyzed Autotandem C–C/C–C Bond-Forming Reactions with Tosylhydrazones: Synthesis of Spirocycles with Extended π‑Conjugation

A new Pd-catalyzed autotandem process is presented by the reaction of tosyl­hydrazones of cyclic ketones and 2,2′-di­bromo­bi­phenyls and related systems. The process involves cross-coupling with tosyl­hydrazone followed by an intramolecular Heck reaction and gives rise to spiro­cyclic structures. Noteworthy, two C–C_Ar bonds are formed on the hydrazonic carbon during the process. Depending on the starting dibromide, an array of spiro­fluorenes, spiro­di­benzo­fluorenes, spiro­acridines, and spiro­anthracenes have been prepared. Thus, this methodology may be applied for the preparation of interesting structures useful in the development of optoelectronic materials.