Synthesis and Reactivity of Allenylporphyrins

Shane Plunkett, Katja Dahms, Mathias O. Senge
2013 European Journal of Organic Chemistry  
Several different methods have been utilized in an effort to allow for the effective the effective synthesis of a new class of porphyrins, bearing the synthetically intriguing propadienyl (or allenyl) functional group. Of these, successive HWE couplings proved impossible, but Pd-catalyzed cross couplings enabled quick and easy synthetic access to allenylporphyrins. Suzuki-Miyaura cross coupling conditions of bromoporphyrins with allenylboronic acid pinacol ester were optimized and represent the
more » ... first successful use of this boronic acid in a Suzuki-type coupling. While this routine proved successful for the synthesis of porphyrins possessing aromatic substituents a more robust method involving Sonogashira coupling of a bromoporphyrin with N,Ndiisopropylprop-2-yn-1-amine followed by Pd catalyzed rearrangement was developed to give allenylporphyrins in high yields. The applicable metalation states of the porphyrin core were also investigated in both routes with mixed results. The utility of the addition of the allenyl functional group was then probed using both directly linked allenylporphyrins and those bearing a phenyl "spacer". ____________ [a]
doi:10.1002/ejoc.201201535 fatcat:ddjmjghuefagtfobny53rnkpsi