Development of Nickel and Zirconium Mediated Cycloadditions for the Synthesis of Substituted Pentacene

Abstract

The regioselectivity of the [2+2+2] cycloaddition of nickel-benzynes and 1,3-diynes could be maintained when asymmetrically substituted 1,3-diynes were employed. The ability to incorporate an asymmetric 1,3-diyne into the oligoacene backbone provided substituents that could be differentiated in subsequent reactions. Conversion of silyl alkynes to bromo alkynes allowed Bergman aromatization of the naphthalenes to occur. The substituted anthracenes formed could then be treated with bis(triphenylphosphine)dichloro-nickel(II) and sodium amalgam to produce a nickelaryne. Application of the [2+2+2] cycloaddition methodology to the longer nickel-aryne in the presence of a 1,3-diyne resulted in an iterative pathway for the synthesis of substituted pentacene. Preliminary efforts for the direct polymerization of poly[n]acene are herein described including the investigation of a possible [4+2] cycloaddition of zirconium-benzyne and 1,3-diynes.