Regioselektive 1,3-Dipolare Cycloadditionen eines ‘Thiocarbonyl-methanids’ ((Alkylidensulfonio)methanids) mit aromatischen Sulfinen

摘要: Reaction of the spirocyclic 2,5-dihydro-l,3,4-thiadiazole 7 and thiobenzophenone S-oxide (6a) in THF at 45° yielded 1,3-dithiolane 1-oxide 8, thiirane 9, diazane derivative 10 a ratio 61:15:23 (Scheme 2). The formation 8 is rationalized by 1,3-dipolar cycloaddition ‘thiocarbonyl-methanide’ 1, generated from thermal elimination N2, C=S bond sulfine 6a. Cyclization intermediate 1 leads to 9. Under same conditions, adamantane-2-thione (6b) or 2,2,4,4-tetramethyl-3-thioxocyclobutanone (4) reacted give only 9 but no cycloadduct type 4 ). With aim favor mixture 6a 1.1 equiv. was heated without any solvent sealed tube. products slightly different that thermolysis THF. An analogous experiment with 9H-fluorene-9-thione (6c) 13 5 It most interesting cycloadditions sulfines 6c proceeded regioselectivity. A reaction mechanism for unexpected proposed Scheme 7. key step base-catalyzed ring opening nucleophilic addition thereby formed thiolate 21 onto sulfonium ion 19