Fluorinated dihydroindeno[2,1-c][1,2,6]thiadiazines: The first synthesis, structural characterization and reactivity

3-(1-Amino-2,2,2-trifluoroethyliden)-1,1,4,5,6,7-hexafluoro-2-iminoindan (1) and 3-(1-amino-2,2,2-trifluoroethyliden)-1,1,4,5,6,7-hexafluoro-2-methyliminoindan (7) reacted with SOCl2 to give previously unknown 4a-chloro-5,6,7,8,9,9-hexafluoro-4-(trifluoromethyl)-4a,9-dihydroindeno[2,1-c][1,2,6]thiadiazine (2) and 5,6,7,8,9,9-hexafluoro-1-methyl-4-(trifluoromethyl)-1,9-dihydroindeno[2,1-c][1,2,6]thiadiazine 2-oxide (8), respectively. When treated with methanol, compound 2 formed 5,6,7,8,9,9-hexafluoro-4a-methoxy-4-(trifluoromethyl)-4a,9-dihydroindeno[2,1-c][1,2,6]thiadiazine (9), whereas the reaction with water gave 5,6,7,8,9,9-hexafluoro-4-(trifluoromethyl)-3,9-dihydroindeno[2,1-c][1,2,6]thiadiazine 2-oxide (5). The latter reacted with SOCl2, acetyl chloride and trifluoroacetic anhydride to give compound 2, 5,6,7,8,9,9-hexafluoro-4-(trifluoromethyl)-4a,9-dihydroindeno[2,1-c][1,2,6]thiadiazin-4a-yl acetate (13) and trifluoroacetate 15, respectively. Solution of compound 2 in trifluoromethanesulfonic acid generated 5,6,7,8,9,9-hexafluoro-4-trifluoromethyl-9H-indeno[2,1-c][1,2,6]thiadiazinylium (11), which was transformed, under the action of water, to sulfoxide 5. The structures of compounds 8, 9, 13 were confirmed by single crystal X-ray diffraction. The reaction pathways were analyzed on the basis of DFT calculations

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► The first synthesis of fluorine-containing dihydroindeno[2,1-c][1,2,6]thiadiazines.
► Nontrivial chemical properties.
► Multinuclear NMR spectroscopy and single crystal X-ray diffraction.