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–CAr 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.