FORMATION OF 1,2,4-TRITHIOLANES IN 3-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 thiokctones 18 (two-component reaction) at 80 degrees yields only the correspending 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(4H) (24) instead of aromatic thioketone 18. imine 25, trithiolane 21a. and 1.4,2-dithiazolidine 26 art Termed (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.