The simplest hemiindigo, 5a (Table ), has been reported in the literature. The typical procedure for the synthesis of Z-5a is a twostep, one-pot protocol that involves an initial hydrolysis of an acetate (base, methanol, 100C) and subsequent condensation with a respective aldehyde, which usually requires several hours to days in solvents like methanol, toluene or DMF. The purification process of Z-5a involves neutralization and subsequent purification via extraction or chromatography. An inert atmosphere is required to minimize side reactions leading to indigo formation as a byproduct (Scheme 1). Even with this precaution, the formation of indigo can rarely be completely avoided, presenting significant challenges to the purification process and photophysical studies. This is due to indigo's low, though not insignificant, solubility in most solvents and its strong UV/Vis absorption.