One-Pot Reductive Methylation of Nitro- and Amino-Substituted (Hetero)Aromatics with DMSO/HCOOH: Concise Synthesis of Fluorescent Dimethylamino-Functionalized Bibenzothiazole Ligands with Tunable Emission Color upon Complexation was written by Osusky, Patrik;Smolicek, Maros;Nociarova, Jela;Rakovsky, Erik;Hrobarik, Peter. And the article was included in Journal of Organic Chemistry in 2022.Formula: C7H4N2O2S This article mentions the following:
One-pot reductive N,N-dimethylation of suitable nitro- and amino-substituted (hetero)arenes e.g., 6-nitrobenzothiazole can be achieved using a DMSO/HCOOH/Et3N system acting as a low-cost but efficient reducing and methylating agent. The transformation of heteroaryl-amines can be accelerated by using DMSO/oxalyl chloride or chloromethyl sulfide as the source of active CH3SCH2+ species, while the exclusion of HCOOH in the initial stage of the reaction allows avoiding N-formamides as resting intermediates. The developed procedures are applicable in multigram-scale synthesis, and because of the lower electrophilicity of CH3SCH2+, they also work in pathol. cases, where common methylating agents provide N,N-dimethylated products e.g., I in no yield or inferior yields due to concomitant side reactions. The method is particularly useful in one-pot reductive transformation of 2-H-nitrobenzazoles to corresponding N,N-dimethylamino-substituted heteroarenes. These, upon Cu(II)-catalyzed oxidative homocoupling, afford 2,2′-bibenzazoles II (Z = S, NMe; R1 = H, Me; R2 = H, N(Me)2; R3 = H, N(Me)2) substituted with dimethylamino groups as charge-transfer N,N ligands with intensive absorption/emission in the visible region. The fluorescence of NMe2-functionalized bibenzothiazoles II remains intensive even upon complexation with ZnCl2, while emission maxima are bathochromically shifted from the green/yellow to orange/red spectral region, making these small-mol. fluorophores, exhibiting large emission quantum yields and Stokes shifts, an attractive platform for the construction of various functional dyes and light-harvesting materials with tunable emission color upon complexation. In the experiment, the researchers used many compounds, for example, 6-Nitrobenzothiazole (cas: 2942-06-5Formula: C7H4N2O2S).
6-Nitrobenzothiazole (cas: 2942-06-5) belongs to thiazole derivatives. Thiazoles are a class of five-membered rings containing nitrogen and sulfur with excellent antitumor, antiviral and antibiotic activities. Thiazole sulfonation occurs only under forcing conditions: the action of oleum at 250 °C for 3 hours in the presence of mercury(II) sulfate leads to 65% formation of 5-thiazole sulfonic acid.Formula: C7H4N2O2S
Referemce:
Thiazole | C3H3NS – PubChem,
Thiazole | chemical compound | Britannica