A new chiral benzo[1,2-b:4,5-b′]dithiophene-based oligothiophene has been synthesized and spectroscopically characterized in solution and in the solid state. The electronic circular dichroism (ECD) spectra of the thin films revealed the occurrence of an uncommon phenomenon, consisting of the inversion of the circular dichroism sign by sample flipping. To the best of our knowledge, this is unprecedented in samples where no preferential orientation of the chromophores has been induced, and must be due to spontaneous local anisotropies. It reveals peculiar features upon the usual solvent annealing procedure, but finally results in stable and very strong signals, which are perfectly reproduced in sign, and relative and even absolute magnitude. Although the recorded signal cannot be considered as a true ECD spectrum, it corresponds to a very large discrimination of light circular polarization, which is well explained by means of the Mueller matrix analysis and does not depend on instrumental defects. It is a genuine property of this material, which correlates with polarized optical microscopy (POM) images and only depends on the self-assembling properties of this molecule. This phenomenon may have relevant implications, on account of its strength and of the interest of oligothiophenes in current optoelectronic devices.

The acyl Sonogashira reaction represents an extension of Sonogashira cross-coupling to acid chlorides which replace aryl or vinyl halides, while terminal acetylenes are used as coupling partners in both reactions. The introduction of a carbonyl functional group on the alkyne backbone determines a radical change in the reactivity of the products. Indeed, α,β-alkynyl ketones can be easily converted into different heterocyclic compounds depending on the experimental conditions employed. Due to its potential, the acyl Sonogashira reaction has been deeply studied with particular attention to the nature of the catalysts and to the structures of both coupling compounds. Considering these two aspects, in this review, a detailed analysis of the literature data regarding the acyl Sonogashira reaction and its role in the synthesis of several heterocyclic derivatives is reported.