115. 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 Dithiobenzoesaeure-methylester

Article abstract of DOI:10.1002/hlca.19950780609

Reaction of PhN3 with O-methyl thiobenzoate (11a) and thioacetate (11c) as well as with the dithio esters 11b, d at 80 deg C 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 13 and 3a are trapping products of 1a and 'thiocarbonyl-aminide' 5a and 'thiocarbonyl-amidine' 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.