The Use of Cobalt-Mediated Cycloisomerisation of Ynedinitriles in the Synthesis of Pyridazinohelicenes

Abstract

A cobalt-mediated [2+2+2] cycloisomerisation of ynedinitriles to helical pyridazines in good to high yields was developed. The construction of the pyridazine nucleus from one alkyne and two nitrile units is proposed to follow either a conventional organometallic mechanism or to be triggered by a single-electron transfer from a Co-II species.

Various [5]-, [6]- and [7]helicene pyridazines were prepared.

Keywords

• cobalt
• cyclization
• helical structures
• heterocycles
• radicals