Reactions of azulene and guaiazulene with all-trans-retinal and trans-cinnamaldehyde: comparative studies on spectroscopic, chemical, and electrochemical properties of monocarbenium-ions stabilized by expanded π-electron systems with an azulenyl or 3-gua

A facile preparation, molecular structures, and properties of the delocalized monocarbenium-ion compounds 3-6 are reported.