1,2,3-Thiadiazoles with Unsaturated Side Chains; Synthesis, Polymerization, and Photocrosslinking

Abstract

1,2,3-Thiadiazoles with polymerizable functionalities in the 4-position were synthesized as potential negative photoresists. The polymerization to soluble, film-forming materials must leave the heterocyclic rings intact, because they are needed for photocrosslinking reactions to give insoluble materials. 1,2,3-Thiadiazoles 1 cycloeliminate N 2 on irradiation. The resulting 1,3-diradicals 2 have various options for stabilization processes leading to alkynes 3 or to higher heterocycles 5-12. The generation of atomic sulfur and its involvement in these subsequent reactions must be avoided. Therefore, systems like model compound 1a, in which the 1,3diradicals form 2-methylene-1,3-dithioles (dithiafulvenes) 9 were selected here. Optimization gave ultimately two materials for application as photoresists. Monomer 1c could be polymerized in the presence of boron trifluoride to soluble 1c¢, which on irradiation formed 1c¢¢ as a cross-linked insoluble polymer. Furthermore, thiadiazole 1f was attached to polystyrene 26. The resulting soluble polymer 1i¢ yielded the insoluble material 1i¢¢ on irradiation.

Synthesis, antimicrobial and in vitro antitumor activities of a series of 1,2,3-thiadiazole and 1,2,3-selenadiazole derivatives

“…1,2,3-Thiadiazole derivative 4a was prepared from the corresponding ketone 1a, as described previously 19 but with a different methodology, as shown in Figure 1 . The synthetic procedure started from ketone 1a that was prepared following a specific procedure.…”

“…The synthetic procedure started from ketone 1a that was prepared following a specific procedure. 19 Ketone 1a was transformed into the corresponding epoxide derivative 2a through oxidation with m-chloroperbenzoic acid. The hydrazone derivative 3a was obtained from the condensation reaction between compound 2a and ethyl carbazate.…”

Mechanistic Investigations on the Photoisomerization Reactions of Five-Membered Ring Heterocyclic Molecules Containing Sulfur and Selenium Atoms

“…1,2,3-Thiadiazoles and their derivatives have attracted intense interest because of their use in the study of fundamental chemistry problems and potential applications . It is well-accepted that various 1,2,3-thiadiazoles can exhibit biological activity such as antibacterial, antiviral, , antitumor, antiallergic, systemic acquired resistance, , fungicidal, − and insecticidal activity, as well as being DNA photocleavers and reagents in photolitography. − Also, 1,2,3-thiadiazoles have been introduced into other active compounds as an active moiety for lead discovery …”

“…To the best of our knowledge, so far, there has been neither experimental nor theoretical study for the photochemical mechanisms of both 1 and 6 . It is astonishing how little is known about the mechanisms of the photochemical reactions of 1 and 6 because these molecules are so important in bioorganic and organic chemistry. − Accordingly, using a more sophisticated quantum chemical theory, the study of the potential energy surfaces of 1,2,3-thiadiazole ( 1 ) and 1,2,3-thiadiazole ( 6 ) systems is undertaken. The goal of this study is to combine both observed experimental works and theoretical examinations to provide a comprehensive understanding of the excited-state behaviors of 1,2,3-thiadiazoles and 1,2,3-selenadiazoles.…”

Early Events in the Photochemistry of 1,2,3-Thiadiazole Studied by Ultrafast Time-Resolved UV–Vis and IR Spectroscopies

“…1,2,3-Thiadiazoles and their derivatives make up an important class of molecules in organic synthesis , and medicinal chemistry and have received particular attention as photo-cross-linkers in biology and chemistry, , DNA photocleavers, and reagents in photolitography. , Light-induced extrusion of molecular nitrogen from 1,2,3-thiadiazoles leads to the formation of intermediates such as thiirene and thioketene, whose presence was deduced from studies of photolyzed products or indicated by direct observation by means of infrared spectroscopy in cryogenic matrices. − In the latter studies Krantz and Laureni have established that photolysis of 1,2,3-thiadiazoles 1 (Scheme ) results in thiirene 3, thioketene 4 , and ethynethiol 5 . − The existence of the intermediate 1,3-diradical 2 cannot be claimed as certain (see review ). Moreover, its experimental detection would be difficult if the 1,3-diradical was unstable as implied by computational studies placing thioketene, ethynethiol, and thiirene well below the 1,3-diradical in energy. , Alternatively, these products may be born directly in the thiadiazole excited state in concert with nitrogen extrusion (rearrangement in excited state, RIES), by analogy to ketene formation in photoinduced concerted process in diazo carbonyl compounds …”