The starting materials in the Piloty-Robinson pyrrole synthesis are 2 equivalents of an and . The product is a pyrrole with specific substituents in the 3 and 4 positions. The aldehyde reacts with the diamine to an intermediate di- (R–C=N−N=C–R), which, with added , gives ring-closure and loss of to the pyrrole.
Six meso-substituted dipyrromethanes were prepared by the reaction of 2-(-decylthio)pyrrole/aldehyde/InCl3 (2.2:1:0.2 ratio) followed by hydrodesulfurization.
Synthesis and characterization of Boc-protected 4 …
N2 - (Chemical Equation Presented) The synthesis of N-acyl 3,4-disubstituted pyrroles can be accomplished directly from hydrazine and an aldehyde via a Piloty-Robinson pyrrole synthesis. The use of microwave radiation for the cyclization and pyrrole formation greatly reduces the time necessary for this process and facilitates moderate to good yields from hydrazine for the corresponding 3,4-disubstituted products (5-12). By simple hydrolysis, the free N-H pyrroles can be accessed after the Piloty-Robinson reaction and then used directly in the synthesis of octaethylporphyrin (H2OEP, 14) and octaethyltetraphenylporphyrin (H2OETPP, 15).