Pd-Catalyzed autotandem C-C/C-C bond forming reactions with tosylhydrazones: Synthesis of spirocycles with extended π-conjugation

A new Pd-catalyzed auto-tandem 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 intra-molecular Heck reaction and gives rise to spirocyclic structures. Noteworthy, two C-CAr bonds are formed on the hy-drazonic carbon during the process. Depending on the starting dibromide, an array of spiro fluorenes, spiro dibenzo-fluorenes, spiro acridines. and spiro anthracenes have been prepared. Thus, this methodology may be applied for the preparation of interesting structures useful in the development of optoelectronic materials