A Facile Preparation of (4-Aminophenyl)(3-guaiazulenyl)methyliumHexafluorophosphate: Comparative Studies on Spectroscopic,Chemical, and Electrochemical Properties of Monocarbenium Ionand p-Benzoquinodimethane Monoiminium Ion Compounds

摘要

Reaction of guaiazulene with 4-aminobenzaldehyde in CH3OH in the presence of hexafluorophosphoric acid at25 °C for 2 h gives the title compound, with an equiv of HPF6, in 56% yield. Interestingly, a solution of the obtainednew monocarbenium ion compound, forming a protonated amino group (4-H_3N~+PF_6~-), in CH_3CN is allowed to stand atroom temperature for 48h, gradually converting to a new 4-(3-guaiazulenyl)methylene-2,5-cyclohexadiene-l-iminiumhexafluorophosphate, completely. Furthermore, reductions of the above two products with NaBH_4in a mixed solvent ofEtOH and CH3CN afford 4-amino-1-(3-guaiazulenylmethyl)benzene, selectively. Comparative studies on spectroscopic,chemical, and electrochemical properties of the monocarbenium ion compound with those of the 4-methylene-2,5-cyclohexadiene-l-iminium ion compound, are reported.