1,3-Dipole mit zentralem S-Atom aus der Umsetzung von Aziden mit Thiocarbonyl-Verbindungen: Eine unerwartete MeS-Wanderung im Abfangprodukt eines ‘Thiocarbonyl-aminids’ mit Dithiobenzoesäure-methylester

1,3-Dipoles with a Central S-Atom from the Reaction of Azides and Thiocarbonyl Compounds: An Unexpected MeS Migration in the Trapping Product of a ‘Thiocarbonyl-aminide’ with Methyl Dithiobenzoate Reaction of PhN₃ with O-methyl thiobenzoate ( 11a ) and thioacetate ( 11c ) as well as with the dithio esters 11b,d at 80° yields the corresponding imidates and thioimidates 12 (Scheme 3). The formation of 12 is rationalized by a 1,3-dipolar cycloaddition of the azide and the C?S group followed by successive elimination of N₂ and S. In the three-component reaction of 11b , PhN₃, and the sterically crowded thioketone 1a , 1,2,4-trithiolane 13a and 1,4,2-dithiazolidine 3a are formed in addition to 12b (Scheme 4). The heterocycles 13a and 3a are trapping products of 1a and ‘thiocarbonyl-thiolate’ 5a and ‘thiocarbonyl-aminide’ 2a (Ar?Ph), respectively (Scheme 6). These 1,3-dipoles are formed as reactive intermediates. Surprisingly, in the presence of catalytic amounts of acids, the major product is the (methyldithio)cyclobutyl thioimidate of type 14 (Scheme 5), formed by an acid-catalyzed MeS migration in dithiazolidine 17 . A reaction mechanism is proposed in Scheme 7.