The synthesis and molecular structures of 2,5-diarylpyrroles, $[{\text{pyr}}^{{\text{Ar}}_{\text{2}} } ]$H (Ar = Ph, 2,4-Xyl)

Abstract

2,5-Di(2,4-xylyl)pyrrole, $[{\text{pyr}}^{{\text{2,5 - Xy1}}_{\text{2}} } ]$H, has been synthesized by reaction of the diketone [XylC(O)CH₂]₂ with NH₄OAc in AcOH; the diketone itself is obtained by condensation of XylC(O)Me with XylC(O)CH₂Br in the presence of Ti(OPrⁱ)₄. The molecular structures of both $[{\text{pyr}}^{{\text{2,5 - Ph}}_{\text{2}} } ]$H and $[{\text{pyr}}^{{\text{2,5 - Xy1}}_{\text{2}} } ]$H have been determined by single crystal X-ray diffraction, thereby demonstrating that an ortho methyl substituent increases the dihedral angle between the aryl and pyrrolyl groups from 14.5° in $[{\text{pyr}}^{{\text{2,5 - Ph}}_{\text{2}} } ]$H to 24.1° in $[{\text{pyr}}^{{\text{2,5 - Xy1}}_{\text{2}} } ]$H.