Synthesis of photochromic dithienylethenes having quinoline and Triazolo[4,3-a]quinoline bridges

Pronounced effects on switching efficiency of diarylcycloalkenes upon cycloalkene ring contraction

“…On the other hand, extended p-conjugation has little effect on the quantum yields of ring closure in the C5F-compounds but causes a huge decrease in the quantum yields of ring closure in the C4F-compounds. Altogether, these findings reveal the important role of ring tension in the [4,6]-ring system, which supports the opening of the cyclohexadiene ring in the closed form but impedes its closing in the open form.…”

“…Fig. 1) positions for functionalizations are mainly the bridging unit A, 4 the heteroatom in the 5-membered-ring (X = CH 2 , S, O, NH), 5 the substituents Y at the reactive center, 6 and the more peripheral substituents R. 7 Whereas wide variations of R and X have been applied for rational design and tuning of photochemical properties, the substituent Y is usually restricted to the methyl group, and the structural element A to a 5-or 6-membered ring.…”

Synthesis and photochromism of some mono and bis (thienyl) substituted oxathiine 2,2-dioxides

“…The change in appearance of the sample is clearly visible from the photograph presented in Figure 6 with the unirradiated sample appearing pale yellow and a post-irradiated sample developing a red / brown hue. [17][18][19][20][21][22] However, it is clear from this study that for good photochromic performance the presence of two substituted thiophene units at the termini of the central ethene bond combined with further unsaturation in the central oxathiine moiety is essential. 1,2 Our exploration of the application of the oxathiine moiety as the central core in photochromic systems continues and is presently focussed on both further extending the lateral conjugation using substituted (hetero)aromatic systems and enhancing the photocolouration process.…”

“…P-type photochromic dithienylethenes such as 1-open, which readily undergoes reversible conversion to the coloured isomer 1-closed, (Scheme 1) are fundamental switching units which have been used to modulate a variety of physical and optical properties. 1 Structural variation of the essential 1,2-bis(2,5-dimethylthiophen-3-yl)ethene core has been frequently explored by modification of the 2,5-dimethylthiophene moiety 1,2 and to a somewhat lesser extent by variation of the perfluorocycle, particularly replacement of the latter with a 5-membered heterocyclic unit to afford 2, wherein the heterocycle has been selected from imidazole, 3,4 imidazolium, 5 pyrrole, 6 thienophosphole, 7 phosphindolothiophene, 8 thiophene, [9][10][11] thiopyranothiophene, 12 silole, 13,14 1,3-dithiole 15 and thiazole 16 and less commonly with a sixmembered unit leading to 2 where the heterocyclic unit includes quinoxaline, 17 triazoloquinoline, 18 pyridazine, 19 thiazine, 20 1,2-oxazine 21 and 1,2,4-triazine. 22…”

An expedient synthesis of thienylacetic acids using the Willgerodt-Kindler reaction under PTC conditions

“…Derivatives of 3-thienylacetic acids are important intermediates in the synthesis of drugs, 1 pesticides 2 and multifunctional photochromic molecular systems possessing fluorescent, [3][4][5] magnetic 6 and complexing properties. 7 The basic methods used for the synthesis of these compounds are based on hydrolysis of the corresponding nitriles, 8 the reduction of ketoacids, 9 Arndt-Eistert 10 and Willgerodt-Kindler 11 reactions.…”