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

Org Lett. 2014 Apr 18;16(8):2264-7. doi: 10.1021/ol500778u. Epub 2014 Apr 7.

Abstract

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.