Bildung von 1,2,4‐Trithiolanen in Dreikomponenten‐Gemischen aus Phenyl‐azid, aromatischen Thioketonen und 2,2,4,4‐Tetramethylcyclobutanthionen: Eine Schwefel‐Transfer‐Reaktion unter Bildung von ‘Thiocarbonylthiolaten’ ((Alkylidensulfonio)thiolaten) als reaktive Zwischenstufen

Formation of 1,2,4‐Trithiolanes in Three‐Component Reactions of Phenyl Azide, Aromatic Thiones, and 2,2,4,4‐Tetramethylcyclobutanethiones: A Sulfur‐Transfer Reaction to ‘Thiocarbonyl‐thiolates’ ((Alkylidenesulfonio)‐thiolates) as Reactive Intermediates The reaction of PhN 3 and aromatic thioketones 18 (two‐component reaction) at 80° yields only the corresponding imines 22 , S, and N 2 . Under similar conditions, in the presence of sterically crowded 2,2,4,4‐tetramethyl‐cyclobutanethiones 19 (three‐component reaction), 1,2,4‐trithiolanes of type 20 are formed in good yields in addition to imines 22 ( Scheme 4 ). In case of 19a and 19c (X = CO, CS), the symmetrical trithiolanes 21a and 21b , respectively, are also isolated. With 4,4‐dimethyl‐2‐phenyl‐1,3‐thiazole‐5(4 H )‐thione ( 24 ) instead of aromatic thioketone 18 , imine 25 , trithiolane 21a , and 1,4,2‐dithiazolidine 26 are formed ( Scheme 5 ). A reaction mechanism for the formation of 1,2,4‐trithiolanes 20 and 21 , including an S‐transfer to generate ‘thiocarbonyl‐thiolates’ 2b and/or 2c and 1,3‐dipolar cycloaddition with a thioketone, is proposed in Scheme 7 .