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A series of thiazolo[5,4-d]thiazoles with bipolar character has been designed and synthesized. Compounds 4a-d and 5a,b consist of a central thiazolo[5,4-d]thiazole as the electron acceptor (A) and a terminal 9,9´-spirobifluorene...

The acid catalysed triple self-condensation of 1-thien-2-ylethanone (2-acetylthiophene) and five related compounds is presented. Tetrachlorosilane used as the Lewis acid produces dry hydrogen chloride which catalyzes the self-condensation process. Depending on the reaction conditions and the substitution of the carbonyl substrates, the reaction can proceed as a [2+2+2] cyclotrimerization towards C 3 -symmetric 1,3,5trisubstituted benzenes, or as the single-type aldol condensation leading to 1,3-disubstituted (E)-β-methylchalcones. This is important for the design of new aromatic/olefinic compounds beyond the model structures. Synthesis of 4'-fluoro-3,5-di-(2-thienyl)biphenyl through a mixed-type aldol reaction using erbium triflate is discussed. Mechanistic rationale is provided.

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Substituted thiophene-2-carbaldehydes 1a-d were utilized in the synthesis of symmetrically substituted thiazolo [5,4-d]thiazoles 3a-d. Bis(5,thiazoles with thiophene core at the termini are the most employed in the chemistry of materials but exhibit insufficient solubility in majority of organic solvents with notable impact on the low yields of products. Accordingly, the synthetic approach towards 2,5-dithiophen-2-yl-thiazolo [5,4-d]thiazole (3a) and its substituted derivatives 3b-d is discussed under the various reaction conditions. Appropriate structural characterisations are included with emphasis on relationship between structure and physicochemical properties highlighting the UV-Vis and fluorescence.